MINI REVIEW   Open Access    

Out of the box thinking: challenges and future perspectives for food-grade nutraceutical delivery systems

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  • Food-grade nutraceuticals often have unstable properties and are easily decomposed under the influence of light, heat, pH, and other conditions during processing and digestion. Moreover, many hydrophobic nutraceuticals are characterized by poor solubility, low bioaccessibility, and low bioavailability, which limits the widespread utilization of food-grade nutraceuticals. With the development of food-grade nutraceutical delivery system technology (FNDS), the utilization barrier of food-grade nutraceuticals has been gradually overcome, so that food-grade nutraceuticals are increasing in their effective used. However, the development of FNDS still faces many challenges. Herein, the safety of FNDS is first discussed. In addition, the stability of FNDS in different environments remains to be improved. Besides, the FNDS also has the challenge of off-target effect. In the future, the development direction of FNDS might be exploring the multi-nutrient co-delivery system, designing new types of FNDS, and clarifying the nutraceuticals release mechanism, and their final fate. The challenges and future perspectives of FNDS have been considered critically and summarized in this review, to promote the development of FNDS and the wide application of nutraceuticals.
  • Huangqin tea (HQT, Fig. 1), also called Huangjin tea in Chinese, has a long history of consumption in China[1]. It is a healthy herbal tea crafted from the aerial parts of Scutellaria baicalensis Georgi, S. scordifolia Fisch, S. amoena C. H. Wrigh, and S. viscidula Bung[24]. Unlike traditional tea made from Camellia sinensis (L.) O. Kuntze, HQT lacks stimulating components and is renowned for clearing heat and dry dampness, eliminating toxins, promoting digestion, and soothing fire[1,5]. It can be enjoyed both as a hot beverage and as a cold drink, and modern research suggests that HQT exhibits several pharmacological properties, such as anti-inflammatory, chemopreventive effects of colorectal cancer[6], anti-aging[7], cardiovascular protection, hypoglycemic effect, hypolipidemic effect, anti-tumor, anti-bacterial, anti-influenza virus, and enhance human resistance[812]. The predominant compounds found in HQT are flavonoids and essential oils and its potential health benefits are likely attributed to the presence of distinctive flavonoids, including isocarthamidin-7-O-β-D-glucuronide, carthamidin-7-O-β-D-glucuronide, apigenin-7-O-β-D-glucopyranside, chrysin-7-O-β-D-glucuronide, scutellarin, baicalin, wogonoside, and chrysin[1318].

    Figure 1.  The aerial parts of S. baicalensis Georgi, dried and brewed Huangqin tea.

    HQT is made using simple ingredients and has a straightforward preparation method. Traditionally, the above-ground portions of Scutellaria species have been utilized for crafting HQT, with the differentiation between stems and leaves remaining unessential. During the hot summer season (July to August), the aerial parts (stem, leaves, flowers) of these species of Scutellaria from a single source are collected and cut into small sections, which are then directly dried for later use. Alternatively, freshly harvested branch and leaf sections may undergo a transformative process through multiple rounds of steaming and subsequent drying within a steamer. Once suitably conditioned, they find their place within sealed containers, poised for extended storage periods. The brewing ritual commences by incorporating 7−8 g of this tea into 2 L of water, with subsequent replenishments of water at intervals 2−3 times. As the brewing ritual concludes, HQT graces the senses with a resplendent golden infusion—earning it another name, 'Huangjin tea'.

    HQT boasts a range of health advantages and is frequently gathered from the upper sections of Scutellaria species plants cultivated in the vicinity, intended for tea consumption. In recent years, large planting bases have been established in several regions, such as Beijing, Inner Mongolia Wuchuan, Yakeshi, Hebei Chengde, Shanxi Province, and Shandong Province, to comprehensively develop S. baicalensis resources. HQT has gained more attention and is now produced by specialized operating companies in various grades, such as bulk tea, bagged tea, and unique tea culture[12].

    To provide up-to-date information on the chemical composition, bioactivity, and safety aspects of the Scutellaria genus from HQT, this review paper has collected related literature from various databases, such as PubMed, Web of Science, Sci Finder, Scopus, Baidu Scholar, China National Knowledge Internet (CNKI), Wanfang and Weipu Data. This paper aims to draw attention to the need for further research and application of HQT in preventing and managing certain chronic diseases.

    HQT can be derived from several Scutellaria species. S. baicalensis is the most extensively cultivated, with a significant biomass in its aerial parts. Consequently, the primary source of HQT is the aerial part of S. baicalensis, and research focused on these aerial parts is also the most extensive.

    The aerial part and the root of S. baicalensis share similarities in their primary constituents, notably the significant presence of flavonoids, which are regarded as the main active components. However, there are specific chemical differences between the above-ground and underground parts of S. baicalensis. Our preliminary experiments have revealed the disparities in chemical composition between these two parts[18]. Notably, the root of S. baicalensis finds its primary use in medicinal applications, characterized by notably higher expression levels of specific 4′-deoxyflavones compared to the aerial organs. In contrast, the above-ground parts of the plant are employed to prepare tea. This differentiation in utilizing these plant components reflects the accumulated wisdom of generations cultivated through extensive periods of tasting and experience.

    This section provided an in-depth review of the chemical composition of the plant from which HQT is derived. Additionally, a specific emphasis on reviewing the aerial parts of S. baicalensis, which serve as the primary source of HQT has been placed.

    In the 1970s, researchers began to study the chemical composition of the aerial parts of S. baicalensis. The flavonoids are the most abundant chemical components in the aerial parts (flowers, stems, and leaves), and about 54 flavonoid compounds were identified (Table 1, Fig. 2). Most of them are flavonoids, dihydro flavonoids, and glycosides. The main glycoside-forming sugars are arabinose, glucose, and glucuronide, with the most abundant glucuronide glycosides. The optimization of extraction processes can yield a remarkable total flavonoid content of up to 5% in the stems and leaves of S. baicalensis[19].

    Table 1.  Flavonoids of HQT.
    NumberNameFormulaSpeciesRef.
    12',5-Dihydroxy-3',6,7,8-tetramethoxyflavoneC19H18O8S. baicalensis[17]
    22',6-DihydroxyflavoneC15H10O4S. baicalensis[16]
    33',4',5,5',7-PentamethoxyflavoneC20H20O7S. baicalensis[16]
    44',5-Dihydroxy-3',5',6,7-tetramethoxyflavoneC19H18O8S. baicalensis[22,27]
    54',5-Dihydroxy-7-methoxyflavanoneC16H14O5S. baicalensis[16]
    65,4′-Dihydroxy-6,7,8,3′-tetramethoxyflavoneC19H18O8S. baicalensis[17]
    75,2′-Dihydroxy-6,7,8-trimethoxyflavoneC18H16O7S. baicalensis[17]
    85,2′-Dihydroxy-6,7,8,3′-tetramethoxyflavoneC19H18O8S. baicalensis[17]
    95,2′-Dihydroxy-7,8-dimethoxyflavoneC17H14O6S. baicalensis[17]
    105,2′-Dihydroxy-7,8,6′-trimethoxyflavoneC18H16O7S. baicalensis[17]
    115,6,7,3',4'-Pentahydroxyflavone-7-O-glucuronideC21H20O13S. baicalensis[13]
    125,6,7,4'-TetrahydroxydihydroflavoneC15H12O6S. baicalensis[17]
    135,6,7-Trihydroxy-4'-methoxyflavoneC16H12O6S. baicalensis[15]
    145,7-Dihydroxy-6-methoxyflavanonC16H14O5S. baicalensis[17]
    155,7,4′-Trihydroxy-6-methoxyflavanoneC16H14O6S. baicalensis[22]
    165,7,4'-TrihydroxyflavanoneC15H12O6S. baicalensis[13]
    17(2S)-5,7,8,4'-Tetrahydroxyflavanone 7-O-β-D-glucuronopyranosideC21H20O12S. baicalensis[21]
    18(2S)-5,6,7,4'-Tetrahydroxyflavanone 7-O-β-D-glucuronopyranosideC21H20O12S. baicalensis[21]
    196-Hydroxyluteolin-7-O-glucuronideC21H18O13S. baicalensis[13]
    207-MethoxychrysinC16H14O4S. baicalensis[16]
    21ApigeninC15H10O5S. baicalensis, S. amoena,
    S. scordifolia, S. viscidula
    [17,2125]
    22Apigenin-4'-glucopyransideC21H20O10S. baicalensis[17]
    23Apigenin-6-C-glucoside-8-C-arabinosideC26H28O14S. baicalensis[13]
    24Apigenin-7-O-β-D-glucopyransideC21H20O10S. baicalensis[17]
    25Apigenin-7-O-β-D-glucuronideC21H18O11S. baicalensis, S. amoena,
    S. scordifolia
    [13,23,24]
    26Apigenin-7-O-methylglucuronideC22H20O11S. baicalensis[28]
    27BaicaleinC15H10O5S. baicalensis, S. amoena,
    S. scordifolia, S. viscidula
    [2225]
    28Baicalein-7-O-D-glucopyransideC21H20O10S. baicalensis[22]
    29BaicalinC21H18O11S. baicalensis, S. amoena,
    S. scordifolia, S. viscidula
    [16,2325]
    30CarthamidinC15H12O6S. baicalensis[13,20]
    31Carthamidin-7-O-β-D-glucuronideC21H20O12S. baicalensis[22]
    32ChrysinC15H10O4S. baicalensis, S. amoena,
    S. scordifolia
    [13,2124]
    33Chrysin-7-O-β-D-glucuronideC21H20O9S. baicalensis, S. amoena[23,29]
    34DihydrobaicalinC21H20O11S. baicalensis[22,28]
    35Dihydrooroxylin AC21H20O11S. baicalensis[13]
    36GenkwaninC16H12O5S. baicalensis[16]
    37IsocarthamidinC15H10O6S. baicalensis[20,28]
    38Isocarthamidin-7-O-β-D-glucuronideC21H20O12S. baicalensis[28]
    39IsoschaftsideC26H28O14S. baicalensis[13,16]
    40IsoscutellareinC15H10O6S. baicalensis[21,30]
    41Isoscutellarein 8-O-β-D-glucuronideC21H18O12S. baicalensis[21]
    42Kaempferol 3-O-β-D-glucopyranosideC21H20O11S. baicalensis[13,28]
    43LuteolinC15H10O6S. baicalensis[22,30]
    44Norwogonin-7-O-glucuronideC21H18O12S. baicalensis, S. amoena[13,17,23]
    45Oroxylin AC16H12O5S. baicalensis, S. amoena[17,23]
    46Oroxylin A-7-O-D-glucopyransideC22H22O10S. baicalensis[22,28]
    47Oroxylin A-7-O-β-D-glucuronideC22H20O11S. baicalensis, S. amoena[13,23]
    48PinocembrinC16H12O5S. baicalensis[13]
    49Pinocembrin-7-O-glucuronideC21H20O11S. baicalensis[13,16,22]
    50SalvigeninC18H16O6S. baicalensis[21]
    51ScutellareinC15H10O6S. baicalensis[28]
    52ScutellarinC21H18O12S. baicalensis, S. amoena,
    S. scordifolia, S. viscidula
    [2325,29]
    53WogoninC16H12O5S. baicalensis, S. amoena,
    S. scordifolia, S. viscidula
    [2125]
    54WogonosideC22H20O11S. baicalensis, S. viscidula[13,25]
     | Show Table
    DownLoad: CSV
    Figure 2.  Chemical structure of flavonoids in HQT.

    In 1976, Takido et al.[20] isolated two flavanone derivatives, carthamidin and isocarthamidin, for the first time as natural products from the leaves of S. baicalensis. Later, Yukinori et al.[21] identified two new flavanones, (2S)-5,7,8,4'-tetrahydroxyflavanone 7-O-β-D-glucuronopyranoside and (2S)-5,6,7,4'-tetrahydroxyflavanone 7-O-β-D-glucuronopyranoside), in the leaves of S. baicalensis. Eight compounds of chrysin, wogonin, apigenin, salvigenin, scutellarein, isoscutellarein, apigenin 7-O-glucuronide, and isoscutellarein 8-O-glucuronide were also isolated. Wang et al.[15] used column chromatography to isolate seven flavonoids (wogonin, chrysin, 5,6,7-trihydroxy-4'-methoxyflavone, carthamindin, isocarthamidin, scutellarein, and chrysin 7-O-β-D-glucuronide) from a water extract of the leaves of S. baicalensis. Liu et al.[13] identified 21 flavonoids in the stems and leaves of S. baicalensis by HPLC-UV/MS and NMR, and found one flavonone (5,6,7,3',4'-Pentahydroxyflavone-7-O-glucuronide) was a new compound. Zhao[17] firstly isolated 5,6,7,4′-tetrahydroxyflavanone 7,5,7-dihydroxy-6-methoxyflavanone, oroxylin A, 5,4′-dihydroxy-6,7,8,3′-tetramethoxyflavone, 5,2′-dihydroxy-6,7,8,3′-tetramethoxyflavone, 5,2′-dihydroxy-7,8,6′-trimethoxyflavone, 5,2′-dihydroxy-7,8-dimethoxyflavone, 5,2′-dihydroxy-6,7,8-trimethoxyflavone, apigenin 4'-β-D-glucopyranoside, and apigenin-7-β-D-glucopyranoside from the aerial parts of S. baicalensis. Ma[22] firstly isolated 5,7,4'-trihydroxy-6-methoxyflavone, 5,4'-dihydroxy-6,7,3',5'-tetramethoxyflavone, from stems and leaves of S. baicalensis. Wang et al.[16] isolated 5,4'-dihydroxy-7-methoxyflavanone, genkwanin, 7-methoxychrysin, 3',4',5,5',7-pentamethoxyflavone from 60% ethanol extracts for stems and leaves of S. baicalensis for the first time. Also, the compounds of carthamidin-7-O-β-D-glucuronide, oroxylin A-7-O-β-D--glucuronide, and chrysin were isolated from this plant for the first time.

    The concentration of these chemical components in HQT varies depending on the plant part utilized. Employing the HPLC-DAD method, Shen et al.[18] established that the aerial parts (stems, leaves, and flowers) of S. baicalensis are rich in flavonoids, resembling the roots in composition but exhibiting significant disparities in content. The contents of isocarthamidin-7-O-β-D-glucuronide (106.66 ± 22.68 mg/g), carthamidin-7-O-β-D-glucuronide (19.82 ± 11.17 mg/g), and isoscutellarein-8-O-β-D-glucuronide (3.10 ±1.73 mg/g) were the highest in leaves. The content of apigenin-7-O-β-D-glucopyranoside (18.1 ± 4.85 mg/g) and chrysin-7-O-β-D-glucuronide (9.82 ± 5.51 mg/g) were the highest in flowers. HQT has a high content proportion of flavone glycosides, which is closely related to the activity of HQT. The concentrations of the nine main flavonoids in HQT infusions were measured using HPLC. The content of isocarthamidin-7-O-β-D-glucuronide (52.19 ± 29.81 mg/g) was the highest; carthamidin-7-O-β-D-glucuronide (31.48 ± 6.82 mg/g), chrysin-7-O-β-D-glucuronide (10.65 ± 0.40 mg/g) and apigenin-7-O-β-D-glucopyranside (5.39 ± 0.92 mg/g) were found at moderate levels in HQT samples. As for flavone aglycones, scutellarin (12.77 ± 1.14 mg/g), baicalin (1.88 ± 0.48 mg/g), isoscutellarein-8-O-β-D-glucuronide (2.84 ± 0.60 mg/g), wogonoside (0.23 ± 0.02 mg/g) and chrysin (0.03 ± 0.01 mg/g) has lower content in HQT[6].

    Although there are few studies on the chemical constituents of the aerial parts of S. amoena, S. scordifolia, and S. viscidula it has been shown that the compounds of the aerial parts are similar to S. baicalensis. The aerial parts of S. amoena contain the compounds of baicalein, baicalin, oroxylin A, oroxylin A-7-O-β-D-glucuronide, wogonin, chrysin, chrysin-7-O-β-D-glucuronide, norwogonin, 5,7-dihydroxy-6,8-dimethoxyflavone, scutellarin[23]. Zhang et al.[24] identified compounds of chrysin, wogonin, baicalein, apigenin, apigenin-7-O-β-D-glucoside, baicalin, and scutellarin in whole plants of S. scordifolia. The stems and leaves of S. viscidula all contain compounds of wogonoside, apigenin, baicalein, wogonin, baicalin, and scutellarin. The contents of baicalein, wogonoside, wogonin, and apigenin in the stem of S. viscidula were higher than those in the stem of S. baicalensis. In the leaves of the two species, the content of scutellarin was higher, while the content of other compounds was lower[25]. The content of scutellarin in S. viscidula was stem (2.30%) > leaf (1.78%) > flowers (0.38%)[26].

    The aerial parts of S. baicalensis are rich in essential oils, and the taste of HQT is closely related to this. The flowers of S. baicalensis are thought to have a Concord grape aroma, while HQT has a bitter flavor with distinctive herbal notes. Extensive analysis has identified 145 components in the essential oil obtained from the aerial parts of S. baicalensis. These components span various chemical classes, such as alkanes, carboxylic acids, fatty acids, monoterpenes/oxygenated monoterpenes, sesquiterpenes triterpenoids and Vitamins (Supplemental Table S1), which have demonstrated their efficacy in combatting bacteria, reducing inflammation and inhibiting tumor growth[2731]. Among these, major constituents include germacrene D (5.4%−39.3%), β-caryophyllene (29.0%), caryophyllene (18.9%), eugenol (18.4%), caryophyllene (15.2%), caryophyllene oxide (13.9%), (E)-β-caryophyllene (11.6%), 5-en-3-stigmasterol (11.3%), carvacrol (9.3%), thymol (7.5%), vitamin E (7.4%), neophytadiene (7.3%), γ-elemene (6.2%), 1-octen-3-ol (6.1%), allyl alcohol (5.5%), bicyclogermacrene (4.8%), myristicin (4.7%), acetophenone (4.6%), α-amyrin (4.6%), β-amyrin (4.4%), germacrene d-4-ol (4.3%), spathulenol (4.2%), β-pinene (4.1%), α-humulen (4.0%), 1-vinyl-1-methyl-2-(1-methylvinyl)-4-(1-methylethylidene)-cyclohexane (4.0%) are found in the aerial parts of S. baicalensis from different places[2731].

    Takeoka et al.[27] identified 64 components in volatile components of S. baicalensis flowers by solid-phase microextraction and analyzed them by GC and GC-MS. These flowers were collected at San Francisco State University (USA). Among the flower volatiles, the content of β-caryophyllene, germacrene D, δ-cadinene, γ-muurolene, and γ-cadinene were more than 3%. The essential oil obtained from the stem of S. baicalensis is mainly composed of diphenylamine, 2,2-methylenebis (6-tert-butyl-4-methylphenol), bornyl acetate, β-caryophyllene, germacrene D and 1-octen-3-ol.[32]. Gong et al.[28] analyzed and identified the specific chemical constituents of the aerial parts of S. baicalensis by using GC-MS technology and identified 37 compounds in total, such as allyl alcohol, acetophenone, caryophyllene, α-humulene, germacrene D, and γ-elemene. The plant material was collected in the Qinling Mountains in China. Lu et al.[29] found a big difference in essential oil components between the aerial and root of S. baicalensis from Kunming Botanical Garden, Yunnan Province (China). The aerial part of S. baicalensis mainly contained enols and sterols such as neophytadiene and vitamin E. However, it has the same compounds as the roots, such as nerolidol, hexadecanoic acid, 1,2-benzenedicarboxylic acid, squalene, stigmast-4-en-3-one, and partial alkanes. Recently, Wang et al.[31] found the essential oil level of the aerial parts of S. baicalensis was 0.09% (v/w, based on fresh weight) while its density was 0.93 g/mL, and obtained 31 components accounting for 97.64% of the crude essential oil, including sesquiterpenoid, monoterpenoids, phenylpropanoids, and others. It is also reported that the major components of the essential oil from the aerial parts of S. baicalensis were myristicin, eugenol, caryophyllene, caryophyllene oxide, germacrene D, spathulenol, and β-pinene, with eugenol as the most abundant. The sample of the aerial parts were harvested from Tangshan City (China). The composition of S. baicalensis essential oils varies according to the plant part used, geographical location, and growing conditions.

    Zgórka & Hajnos[33] identified the phenolic acid compounds of aerial parts of S. baicalensis by solid-phase extraction and high-speed countercurrent chromatography: p-coumaric acid, ferulic acid, p-hydroxybenzoic acid, and caffeic acid. Chirikova & Olennikov[34] found that the aerial part of S. baicalensis contains 11 kinds of saturated fatty acids and nine kinds of unsaturated fatty acids, among which the palmitic acid content is the highest. Chlorogenic acid, fernlic acid, protocatechuic acid, vanillic acid, rosmarinic acid, caffeic acid, p-hydroxybenzoic acid, and p-coumaric acid were also detected.

    Zhao [17] isolated four sterol compounds: β-sitosterol-3-O-β-D-glucoside, α-apinasterol, β-sitosterol, and four ester compounds: methoxyphaeophorbide, p-hydroxybenethyl ethanol hexadecanoic methyl ester, ethoxyphaeophorbide, and n-octadecanol, lutein from the aerial parts of S. baicalensis.

    It is reported that flavonoids and diterpenes are the two main groups of active constituents in the genus Scutellaria. However, only one diterpene (scutebaicalin) was identified in the stems and leaves of S. baicalensis[35].

    By atomic absorption spectrophotometry, Yuan et al.[36] determined the contents of 11 metal elements in different parts of S. baicalensis. It was found that the leaves and stems of S. baicalensis were rich in Mg, K, Cr, Ni, Co, Fe, Mn, and Pb. Meanwhile, Yan et al.[37] developed an inductively coupled plasma mass spectrometry method and determined 23 kinds of inorganic elements in the stems and leaves of S. baicalensis from eight regions. Although there were no differences in the types of inorganic elements in the stems and leaves of S. baicalensis from the different areas, the content of these elements varied significantly. Among these elements, Fe, Zn, Cu, Mn, Cr, Co, Ni, Sr, B, and Ni were essential human body elements. The content of Al (516.83 μg/g) and Fe (700.62 μg/g) was the highest, while the content of B (31.54 μg/g), Ti (23.10 μg/g), Mn (65.64 μg/g), Sr (62.27 μg/g), and Ba (89.68 μg/g) was relatively high.

    Olennikov et al.[38] studied the water-soluble polysaccharides from the aerial parts of S. baicalensis from Russia and found that the polysaccharides from S. baicalensis gradually accumulated before flowering and progressively decreased after flowering.

    Yan et al.[39] found that the stems and leaves of S. baicalensis were rich in amino acids, and there was no difference in the kinds of amino acids among different producing areas, but there was a significant difference in the contents of amino acids. The content of proline, threonine, glutamic acid, lysine, glutamine, and arginine was higher, and the content of methionine, hydroxyproline, and citrulline was low.

    Several studies have focused on the functional properties of HQT, with increasing attention given to the aerial parts of S. baicalensis as the main raw material for HQT production. S. baicalensis stems and leaves flavonoids (SSF) are considered the functional components of HQT. Modern pharmacology has shown that the flavonoids extracted from the stem and leaf of S. baicalensis have been found to possess anti-inflammatory, anti-bacterial, antiviral, antipyretic and analgesic, anti-tumor, hepatoprotective, antioxidant, hypoglycemic, hypolipidemic, detoxification, myocardial ischemia protection, brain injury protection, and immunomodulatory effects. However, few studies have been conducted on the individual flavonoid compounds in the total flavonoid extract from S. baicalensis. Therefore, this paper aims to summarize and supplement the current research on the functional properties of HQT and its primary raw material (S. baicalensis) extract.

    Injury and infection could lead to inflammation, which plays a key role in the accelerated pathogenesis of immune-mediated disease[40]. Tong et al.[41], Zhou et al.[42], and Zhao et al.[43] found that S. baicalensis stem-leaf total flavonoid (SSTF) could inhibit acute exudative inflammation caused by xylene, glacial acetic acid, and egg white and also have a significant inhibitory effect on chronic inflammatory of granulation tissue hyperplasia. Wang et al.[44] observed the effect of SSTF on the aerocyst synovitis of the rat model and found that it could reduce capillary permeability, reduce the aggregation of neutrophils and basophils in tissues, reduce histamine, bradykinin, and other substances that increase vascular permeability, which is conducive to the recovery of vascular permeability in inflammation. Studies have shown that the SSTF significantly inhibits specific and non-specific inflammatory responses and can regulate the body's cellular and humoral immune functions. The mechanism of action is closely related to the effective reduction of capillary permeability, inhibition of PGE2 and NO synthesis in vivo, reduction of TNF-α expression, and reduction of inflammatory exudation[45,46]. SSTF (200 mg/kg) could balance the CD+4 Tlymphocyte subsets Th1/Th2 cells and the related cytokines IL-10 and IFN-γ in the rheumatoid arthritis model[47]. SSTF (17.5, 35 and 70 mg/kg for 38 d) could significantly improve the impairment of relearning ability and retention ability on memory impairment and nerve inflammation in chronic cerebral ischemia rats, which might be due to the inhibition of the proliferation of astrocyte and balanced the expression of the inflammatory factors in the brain[48]. Besides, the extract of S. baicalensis stem-leaf shows anti-inflammation effects both in vitro and in vivo. In cultured macrophage cells (RAW 264.7), the extract of S. baicalensis stem-leaf showed a strong anti-inflammation effect, which inhibited the expression of IL-1β. Similarly, it suppressed the LPS-induced transcriptional activity mediated by NF-κB in fish aquaculture[49]. S. baicalensis stems and leaves (3, 6, and 12g /kg, gavage for 7 d, once per day) have anti-inflammatory effects on 2% carrageenan-induced acute pleurisy in rats, and the mechanism of action may be related to the reduction of the production of inflammatory factors and the down-regulation of TRPV1 signaling protein[50]. The combination of S. baicalensis stems- Polygonum cuspidatum (3.5, 7, and 14 g/kg, gavage for 7 d) has a protective effect on lipopolysaccharide-induced acute lung injury rats, and its mechanism may be related to down-regulating the expression of TRPV1 and inhibiting the levels of TNF-α and IL-1β in inflammatory cells[50]. It is also reported that S. baicalensis stem-leaf combined with Morus alba (4, 8, and 16 g/kg/d, gavage, 10 d) has a protective effect on rats with acute pneumonia induced by lipopolysaccharide, and the mechanism might be related to the reduction of inflammatory factors and the down-regulation of TRPV1 signaling pathway[51]. Besides, the network pharmacology showed that S. baicalensis stem-leaf could prevent and control COVID-19 by intervening in 30 targets and 127 pathways, potentially preventing and treating inflammation caused by COVID-19[52].

    Based on the studies, S. baicalensis stem-leaf extract shows promising anti-inflammatory properties. These effects are likely mediated through a combination of factors, including the modulation of immune responses, reduction of inflammatory mediators, and potential interactions with signaling pathways like TRPV1. However, it's important to note that while these studies provide valuable insights, further research, including clinical trials, is needed to establish the full extent of its benefits and its potential for therapeutic applications in humans.

    Scutellaria baicalensis stem and leaf aqueous extract exhibit different degrees of inhibition of 36 strains from 13 kinds of bacteria, such as Staphylococcus aureus, Staphylococcus, Streptococcus pneumoniae, alpha-hemolytic streptococcus, beta-hemolytic streptococcus and Escherichia coli. This shows that anti-bacterial activity against Staphylococcus aureus is strong (MIC50 0.94 g/L, MBC 0.94 g/L). In vivo (217 mg/kg), it protects against the death of mice infected by Staphylococcus aureus and shows a certain dose-dependence[53]. Zhang et al.[54] found that the stem and leaves of S. baicalensis against Staphylococcus aureus and Shigella dysenteriae with MIC values of 1 and 4 mg/mL, respectively. Besides, it is reported that the water extract of the aerial part of S. baicalensis could inhibit the growth of several common pathogenic bacteria in aquacultures, such as Aeromonas hydrophila, Edwardsiella tarda, Vibrio alginolyticus and V. harveyi[49].

    Zhao et al.[55] found that the active part of the stem and leaf of S. baicalensis could inhibit the cytopathic effect caused by 10 kinds of viruses such as Coxsackie B virus, influenza virus, parainfluenza virus, adenovirus, respiratory syncytial virus, and herpes simplex virus. It is suggested that the active parts of the stem and leaf of S. baicalensis can be used for the prevention and treatment of influenza virus, parainfluenza virus, coxsackievirus, and other related infectious diseases.

    These findings indicate that S. baicalensis stem and leaf extract possess anti-bacterial and antiviral properties, making it a potentially valuable natural resource for combating infections caused by various pathogens. However, while these results are promising, further research, including clinical trials, would be necessary to fully establish the effectiveness and safety of using S. baicalensis extract for preventing or treating bacterial and viral infections, including COVID-19.

    In a series of studies, Tong et al.[41] demonstrated that SSTF at a dosage of 20 mg/kg significantly reduced body temperature in rats with fever induced by subcutaneous injection of a 10% dry yeast suspension. Zhang et al.[56] conducted research on the antipyretic effect of scutellarin, an extract from S. baicalensis stems and leaves, in febrile rabbits and observed an antipyretic substantial impact induced by pyrogen. Yang et al.[57] conducted several animal experiments, where they discovered that intraperitoneal injection of effective doses of SSTF (42.2 and 84.4 mg/kg) exhibited a specific inhibitory effect on infectious fever in experimental animals. Moreover, intraperitoneal injection of appropriate SSTF doses (30.1, 60.3, and 120.6 mg/kg), as found in Yang et al.'s experiments[58], effectively inhibited the pain response in experimental animals. Furthermore, Zhao et al.[59] noted that SSTF exhibited a certain inhibitory effect on the pain response in experimental animals subjected to chemical and thermal stimulation.

    These findings suggest that S. baicalensis stem and leaf extract may have antipyretic and analgesic effects, particularly its total flavonoid component. These effects could be beneficial for managing fever and providing pain relief. However, as with any natural remedy, further research, including controlled clinical trials in humans, is necessary to fully understand the effectiveness, safety, and optimal dosing of S. baicalensis extract for these purposes.

    Amyloid protein (Aβ) has been widely recognized as the initiator of Alzheimer's disease (AD)[60]. The SSTF can improve cognitive function and delay the process of dementia. SSTF has been found to exert neuroprotective effects in AD animal models through various mechanisms. Ye et al.[61] demonstrated that oral administration of SSTF (50 mg/kg) could effectively improve cognitive function and reduce neuronal injury in Aβ25-35-3s -induced memory deficit rats. The underlying mechanisms may involve inhibiting oxidative stress and decreasing gliosis[62,63]. Furthermore, SSTF was shown to reduce Aβ-induced neuronal apoptosis by regulating apoptosis-related proteins Bax and Bcl-2[64]. Subsequent studies further validated the neuroprotective effects of SSTF. Cheng et al.[65] found that SSTF treatment inhibited neuronal apoptosis and modulated mitochondrial apoptosis pathway in composited Aβ rats. Ding & Shang[66] found that the SSF improves neuroprotection and memory impairment in rats due to its inhibition of hyperphosphorylation of multilocus Tau protein in rat brains. SSTF has also been found to exert neurogenesis-promoting effects by regulating BDNF-ERK-CREB signaling[12] and activating the PI3K-AKT-CREB pathway[67].

    In further studies, Ding et al.[11] proposed that the effect of SSF on promoting neurogenesis and improving memory impairment may be related to the regulation of abnormal expression of Grb2, SOS1, Ras, ERK, and BDNF molecules in the BDNF-ERK-CREB signaling pathway. Zhang et al.[68] found that SSF (25, 50, and 100 mg/kg) could significantly modulate okadaic-induced neuronal damage in rats, which provides a basis for evaluating SSF as a means to reduce tau hyperphosphorylation and Aβ expression in Alzheimer's disease. Cao et al.[69] found that SSTF (100 mg/kg, 60 d) may alleviate tau hyperphosphorylation-induced neurotoxicity by coordinating the activity of kinases and phosphatase after a stroke in a vascular dementia rat model. Gao et al.[70] demonstrated that the stems and leaves of S. baicalensis (SSF, 25, 50, and 100 mg/kg/d, 43 d) could inhibit the hyperphosphorylation of tau in rats' cerebral cortex and hippocampus induced by microinjection of okadaic acid, which may be related to the activities of protein kinase CDK5, PKA and GSK3β. Furthermore, Liu et al.[67] demonstrated that SSF (35, 70, and 140 mg/kg/d, 43 d) improved composited Aβ-induced memory impairment and neurogenesis disorder in rats through activated the PI3K-AKT-CREB signaling pathway and up-regulated the mRNA and protein expression of TRKB, PI3K, AKT, CREB and IGF2. More recently, a new study demonstrated that SSF (35, 70, and 140 mg/kg) alleviated myelin sheath degeneration in composited Aβ rats, potentially modulating sphingomyelin metabolism[71]. Collectively, these findings suggest that SSTF holds therapeutic potential for AD by targeting multiple Alzheimer's pathogenesis-related processes.

    Li et al.[72] confirmed that SSTF (5 mg/kg) could improve the behaviors and the numbers of dopaminergic neurons in the substantia nigra in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease in mice, and these beneficial activities appear to be associated with the reduction of the level of serum malondialdehyde.

    These studies suggest that S. baicalensis stem and leaf extract have the potential to exert neuroprotective effects in various neurodegenerative conditions, including Alzheimer's disease and Parkinson's disease. These effects could be attributed to its ability to modulate oxidative stress, apoptosis, signaling pathways, and protein hyperphosphorylation. However, as with any potential therapeutic agent, further research is needed to establish the full extent of its benefits, optimal dosages, and mechanisms of action, as well as its potential applications in human patients.

    In recent years, ischemic cerebrovascular disease has seriously threatened human health. Cerebral ischemia is one of the leading causes of death. It can occur in focal or global ischemia, with most cases associated with ischemic stroke[73]. Neuronal protection against oxidative damage has been proposed as a potential therapeutic strategy to avoid damage during ischemic stroke[74]. It is reported that SSTF can reduce neuronal apoptosis and free radical damage caused by heart and brain ischemia. Zhao et al.[75] have found that the pretreatment of SSTF (100 mg/kg/d) can protect the ischemia-reperfusion myocardium by enhancing the activity of the anti-oxidative enzyme, inhibiting lipid peroxidation and attenuating the oxygen-free radicals-mediated damage to the myocardium in rats. In further studies, Zhao et al.[76] proposed that SSTF (50, 100, or 200 mg/kg/d, 7 d) pretreatment could alleviate the neuronal damage incurred by ischemia-reperfusion, demonstrating a neuroprotective effect in focal ischemia-reperfusion rat model, which may involve the prohibition of the apoptosis of the neurons. Yu et al.[77] confirmed that SSTF (17.5, 35, and 70 mg/kg/d, 7 d) could attenuate cardiomyocyte apoptosis during ischemia reperfusion injury by down-regulating the protein expression of the JAK2 gene. Qin et al.[78] found that SSF (17.5, 35, and 70 mg/kg/d, 38 d) can decrease the expression of the NMDAR in hippocampus, and increase the expression of VEGF in the cerebral cortex of chronic cerebral ischemia rats.

    Focal cerebral ischemia-reperfusion can result in neuronal loss but strongly promotes activation and proliferation of hippocampal glial cells. Losing hippocampal neurons is considered one of the basic pathological mechanisms of cognitive impairment[79]. Zhao et al.[79] found that the pretreatment with SSTF (100 and 200 mg/kg) could improve neurological function after focal cerebral ischemia-reperfusion injury, with preventive and protective effects. Shang et al. found flavonoids from S. baicalensis (35−140 mg/kg) could attenuate neuron injury and improve learning and memory behavior in rats with cerebral ischemia/reperfusion[80]. In further studies, Kong et al.[81] found that the mechanisms of the protective effects on the brain against cerebral ischemia/reperfusion injury of SSTF may involve decreasing the content of brain water, increasing microvascular recanalization, reducing the apoptosis of hippocampal neurons, and attenuating free radical damage. Bai et al.[82] proposed that SSTF (100 mg/kg/d, 7 d) could protect the neurological function in rats following I/R injury by alleviating the damage to the ultrastructure of cerebral cortex neurons and synapse. Yan et al.[83] found that SSTF (100 mg/kg/d, 7 d) pretreatment can exert preventive, protective effects on cerebral tissue by relieving brain edema, decreasing neural damage, promoting microvascular repatency, and increasing enzyme activity. It has been reported that the SSTF may protect neurons and their synaptic structures in multiple ways, but whether this mechanism enhances the resistance of neurons to damage or increases the repair function remains to be further explored.

    Essential hypertension is a common chronic cardiovascular disease, which can lead to multiple target organ damage, such as heart, brain, and blood vessels. It is a risk factor for coronary heart disease, heart failure, and other cardiovascular diseases. It is reported that SSTF (17.5, 35.0, and 70 0 mg/kg, 8 weeks) can inhibit myocardial remodeling in primary hypertensive rats, and the medium dose exerts the best inhibitory effect, and the mechanism may be related to inflammatory response induced by inhibiting the NF-κB signaling pathway[84].

    S. baicalensis stem and leaf extract have the potential to provide neuroprotective effects in conditions related to ischemic cerebrovascular disease and hypertension. Its ability to modulate oxidative stress, inflammation, and apoptotic pathways appears to contribute to its beneficial effects. However, further research is needed to fully understand the mechanisms and optimal usage of SSTF for these therapeutic purposes.

    Aging is associated with the deterioration of physiological function and the decline of cognitive ability[85]. It is reported that the alcohol extracts from roots, stems, leaves, and flowers of S. baicalensis (400 mg/kg, 7 weeks) could regulate the content of differential metabolites in urine samples of D-gal-induced aging-model rats to different degrees and play a certain role in improving the metabolic disorders of aging rats[7]. A further study investigated the anti-aging effects and potential mechanisms of S. baicalensis leaves and flower extract. S. baicalensis leaves (400 and 800 mg/kg, 7 weeks) have an anti-aging effect, which can improve the acquired alopecia, slow response, and other characteristics of aging rats, increase the spontaneous activity of aging rats, and reduce the damage of lipid peroxidation and glycosylation induced by D-galactose[86]. The S. baicalensis flowers extract (400 and 800 mg/kg, 7 weeks) could effectively reverse the cognitive decline and oxidative stress injury and alleviate liver pathological abnormalities in the D -galactose-induced aging rats, which are involved in the glutamine-glutamate metabolic pathway[85].

    S. baicalensis extracts, particularly those from leaves and flowers, may have anti-aging properties by regulating metabolic disorders, improving cognitive function, reducing oxidative stress, and alleviating aging-related physiological abnormalities. However, further research is necessary to fully understand the mechanisms underlying these effects and to determine the potential of these extracts for human applications in addressing age-related issues.

    The SSTF (200 mg/kg d, 35 d) can reduce the joint damage of collagen-induced arthritis mice and balance the CD+4 T lymphocyte subsets Th17 and Treg cells[87]. Besides, on the multiple sclerosis model, the SSTF (100, 200 mg/kg d, 16 d) displayed a protective effect on experimental autoimmune encephalomyelitis rats through a balance of the CD+4 Tlymphocyte subsets Th17 and Treg cells[88]. Zhang et al.[89] have found that SSTF attenuated EAE disease severity, accompanied by enhanced Treg frequency and level of Treg-associated cytokines (IL-10 and TGF-β), as well as downregulated Th17 frequency and expression of Th17-related cytokines (IL-17 and IL-23).

    It is reported that the essential oils from the aerial parts of S. baicalensis showed toxicity against booklice (Liposcelis bostrychophila) with an LC50 of 141.37 μg/cm2. The components of myristate, caryophyllene, eugenol, and caryophyllene oxide displayed dramatic toxicity against the L. bostrychophila, with LC50 values of 290.34, 104.32, 85.75, and 21.13 μg/cm2, respectively[31].

    Guo & Xu[90] have found that SSTF could inhibit the proliferation of Hela cells obviously (p< 0.01). Tang et al.[10] have found that SSTF could play an anti-colon cancer role by up-regulated the expressions of Cleaved Caspase-3 and the ratio of Bax/Bcl-2 (p < 0.05 and 0.01) and significantly down-regulated the expressions of MMP-2 and MMP-9 in HCT116 cells (p < 0.05 and 0.01). Recently, Shen et al.[6] studied the chemopreventive effects of HQT against AOM-induced preneoplastic colonic aberrant crypt foci in rats and found HQT inhibits AOM-induced aberrant crypt foci formation by modulating the gut microbiota composition, inhibiting inflammation and improving metabolomic disorders.

    Cardiovascular disease is one of the most important threats to human health. Hyperlipidemia is a major risk factor for atherosclerosis, which can cause various cardiovascular and cerebrovascular diseases. Different doses of SSTF (50, 100, and 200 mg/kg) can effectively reduce the body weight increase of rats with hypertriglyceridemia, reduce the serum levels of triglyceride(TG), total cholesterol(TC), low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C), which indicate that SSTF has the effect of regulating blood lipid[91].

    Oxidative stress is important in developing tissue damage in several human diseases[92]. The antioxidant capacities of separated organs (flower, leaf, stem, and root) of S. baicalensis were conducted by DPPH, ABTS+, and RP methods, respectively. The results showed that the antioxidant activity of the root (66.9 ± 0.3, 121.6 ± 0.5, and 80.2 ± 0.4 μg/mL) was the highest, followed by the leaf (68.4 ± 1.3, 128.2 ± 2.1, and 135.8 ± 2.0 μg/mL), stem (127.8 ± 3.1, 199.2 ± 1.7, and 208.2 ± 8.3 μg/mL) and flower (129.8 ± 6.3, 285.7 ± 4.7, and 380.3 ± 14.2 μg/mL)[93]. The antioxidant activities of the extracts of the aerial part of S. baicalensis and separated organs were conducted by DPPH assay and reducing power method with the antioxidant ability 7.73–8.83 mg TE/g DW and 51.48–306.09 mg TE/g DW, respectively. The content of total polyphenols and total flavonoids were significantly positively correlated with the reducing power[94]. Liu et al.[95] found that the flavonoids extracted from the stems and leaves of S. baicalensis (SSF, 18.98, 37.36, and 75.92 μg/mL) could protect rat cortical neurons against H2O2-induced oxidative injury in a dose-dependent manner. Cao et al. found that SSTF could alleviate the damage of human umbilical vascular endothelial cells injured by H2O2 and reduce their apoptosis, which may be related to the increasing level of Bcl-2[96].

    Preventive treatment with SSTF (50, 100, and 200 mg/kg) could significantly inhibit the blood glucose increase induced by alloxan in mice, and SSTF treatment could reduce the blood glucose level in diabetic mice. Both the prevention group and the treatment group could increase the activity of serum superoxide dismutase and decrease the content of malondialdehyde[97]. Liu et al.[98] found that SSTF (75 and 150 mg/kg) could significantly reduce blood glucose and blood lipid and improve insulin resistance in type 2 diabetic rats with hyperlipidemia.

    Yang et al.[99] found that SSTF (35 mg/kg/d, 8 weeks) could resist hepatic fibrosis by inhibiting the expression of α-smooth muscle actin in Hepatic Stellate Cells. In vivo, it is reported that SSTF (50, 100, and 200 mg/kg) could significantly reduce alanine transaminase activities in serum, increase the expression of superoxide dismutase and reduce the content of malondialdehyde in acute hepatic injury mice induced by carbon tetrachloride and ethanol[100].

    These findings suggest that S. baicalensis stem and leaf extract hold promise in promoting various aspects of health, including immune modulation, antioxidant activity, anti-tumor effects, cardiovascular health, oxidative stress protection, and more. However, further research, including clinical studies, is necessary to better understand the full therapeutic potential and safety of these effects in human applications.

    Flavonoids are considered the main active components in HQT. As the active substance basis of HQT, the safety of SSTF has also been investigated. After 90 d of oral administration of SSTF (0.5, 1, and 2 g/kg) to rats, no abnormal changes were observed in all indexes, and no delayed toxic reactions or obvious toxic reactions were observed, indicating that the toxicity of SSTF is low[101]. The LD50 value of SSTF was 14.87 g/kg is equivalent to 68.5 times the maximum dose in the pharmacodynamic test of mice, and the experiment confirms the safety of oral administration of the SSTF. Intraperitoneal injection of SST showed certain toxicity in mice, with an LD50 value of 732.11 mg/kg[102]. Liu et al.[103] conducted a systematic safety assessment experiment on the aqueous extract of S. baicalensis stem and leaves based on the China National Standard 'Guidelines for the Safety Evaluation of Food Toxicology (GB15193-2014)'. The results indicated that S. baicalensis stem and leaves are non-toxic, non-teratogenic, and non-mutagenic. Acute toxicity tests in mice revealed a Maximum Tolerated Dose of 15.0 g/kg. A 90-d feeding trial showed no changes in toxicological damage in animals, even at a high dosage of 8.333 g/kg (equivalent to 100 times the recommended human daily intake), suggesting the safety and non-toxicity of consuming S. baicalensis stem and leaves. In addition, HQT has long been used in folklore, and no toxicity has been reported.

    These findings collectively indicate that HQT is generally safe for consumption. However, as with any herbal product, it's important to follow recommended dosages and consult healthcare professionals, especially for individuals with pre-existing health conditions or medications.

    In recent years, HQT, a non-Camellia tea with a long history in China, has attracted attention due to its diverse pharmacological activities. Among various Scutellaria species, S. baicalensis is the most extensively studied and cultivated source for HQT. The aerial parts, including flowers, stems, and leaves, serve as the principal source of HQT preparation. HQT are rich in flavonoids and volatile components with various beneficial effects. To date, about 295 compounds have been identified from HQT, including approximately 54 flavonoid compounds and 145 volatile components identified online. The current research on the activity of HQT primarily focuses on flavonoid compounds, with limited studies on the larger quantity of volatile oil compounds.

    Additionally, the processing and brewing techniques used to prepare HQT may influence the bioactivity of its flavonoid content, although few studies have investigated this. More research is necessary to optimize the processing and brewing techniques to maximize the health benefits of HQT. Comparative studies reveal that the aerial parts of S. baicalensis, while sharing similarities with the roots, contain varying flavonoid compositions. Limited research on S. scordifolia, S. amoena, and S. viscidula, indicates the presence of comparable flavonoid compounds in their aerial parts. Although individual flavonoids like baicalin, wogonin, and scutellarin have demonstrated various therapeutic properties, it is essential to consider the synergistic effects of these compounds when consumed together in the form of tea. These findings contribute to laying the groundwork for quality assessment of HQT and offer insights into potential health benefits.

    HQT is mainly derived from the aerial parts of S. baicalensis. Recent studies have increasingly recognized the pharmacological value of the aerial parts of S. baicalensis. Preliminary pharmacological studies have shown that the aerial parts of S. baicalensis may possess beneficial activities in antioxidant, anti-tumor, antiviral, anti-bacterial, protection of ischemia-reperfusion injured neural function, neuroprotective effects against brain injury, and blood lipid regulation. These findings suggest that the value of using HQT may be attributed to these pharmacological activities. Although HQT is generally safe for consumption, further investigation is required to understand its safety profile, particularly in special populations such as pregnant or lactating women, children, and individuals with pre-existing medical conditions. Additionally, potential interactions between the flavonoids in HQT and conventional medications must be examined to ensure their safe and effective use with pharmaceutical treatments. In addition, although the safe dose of HQT on rodents has been studied, the safe dose for humans has yet to be determined.

    In conclusion, these initial research results support the potential health benefits of HQT and encourage more in-depth studies on its raw materials. Further studies are necessary to elucidate the synergistic effects of the flavonoids in HQT, optimize the processing and brewing techniques for maximum bioactivity, and investigate the safety profile and potential interactions with conventional medications. A comprehensive understanding of HQT will contribute to developing evidence-based recommendations for promoting health and well-being.

    The authors confirm contribution to the paper as follows: Conceptualization and writing: Quan Y, Li Z, Meng X, Li P, Shen J; Figure and table modification: Quan Y, Li Z, Meng X, Li P; review and editing: Wang Y, He C, Shen J. All authors reviewed the results and approved the final version of the manuscript.

    The datasets generated during and/or analyzed during the current study are available from the corresponding author on reasonable request.

    This research was funded by the Shandong Provincial Natural Science Foundation, China (ZR2022QH147, ZR2022QH165) and the Innovation Team and Talents Cultivation Program of National Administration of Traditional Chinese Medicine (No. ZYYCXTD-D-202005).

  • The authors declare that they have no conflict of interest.

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  • Cite this article

    Zhang Y, Wang Y, Zhang K, Lin X, Xue Y, et al. 2024. Out of the box thinking: challenges and future perspectives for food-grade nutraceutical delivery systems. Food Materials Research 4: e027 doi: 10.48130/fmr-0024-0022
    Zhang Y, Wang Y, Zhang K, Lin X, Xue Y, et al. 2024. Out of the box thinking: challenges and future perspectives for food-grade nutraceutical delivery systems. Food Materials Research 4: e027 doi: 10.48130/fmr-0024-0022

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Out of the box thinking: challenges and future perspectives for food-grade nutraceutical delivery systems

Food Materials Research  4 Article number: e027  (2024)  |  Cite this article

Abstract: Food-grade nutraceuticals often have unstable properties and are easily decomposed under the influence of light, heat, pH, and other conditions during processing and digestion. Moreover, many hydrophobic nutraceuticals are characterized by poor solubility, low bioaccessibility, and low bioavailability, which limits the widespread utilization of food-grade nutraceuticals. With the development of food-grade nutraceutical delivery system technology (FNDS), the utilization barrier of food-grade nutraceuticals has been gradually overcome, so that food-grade nutraceuticals are increasing in their effective used. However, the development of FNDS still faces many challenges. Herein, the safety of FNDS is first discussed. In addition, the stability of FNDS in different environments remains to be improved. Besides, the FNDS also has the challenge of off-target effect. In the future, the development direction of FNDS might be exploring the multi-nutrient co-delivery system, designing new types of FNDS, and clarifying the nutraceuticals release mechanism, and their final fate. The challenges and future perspectives of FNDS have been considered critically and summarized in this review, to promote the development of FNDS and the wide application of nutraceuticals.

    • There are many kinds of food-grade nutraceuticals which are derived from a wide range of sources. Some important nutraceuticals have the functions of anti-inflammatory, anti-diabetic, anti-cancerous, and improving digestion, such as resveratrol, naringin, quercetin, carotenoids, fat-soluble vitamins, and flavonoids[1]. Nutrient fortification has been carried out in some foods to improve human health. However, some food-grade nutraceuticals have undesirable flavors, such as tannins, which are strongly astringent[2]. Besides, most food-grade nutraceuticals are highly sensitive to harsh environments, and their bioaccessibility or bioavailability after oral administration is low, which makes their application greatly restricted. For example, when affected by light, heat, and different acid-base conditions during processing, food-grade nutraceuticals often decompose and lose their efficacy[3]. In addition, the high concentration of salt ions, the complex enzyme digestion system, and different kinds of microbiota in the digestive tract will also cause the loss of activity of food-grade nutraceuticals. Even if food-grade nutraceuticals can reach the intestinal tract, their bioaccessibility will be greatly reduced due to their hydrophobicity[1]. If the food-grade nutraceuticals need to enter the bloodstream to work, they must cross three sequential cellular barriers including apical endocytosis, intracellular trafficking, and basolateral exocytosis[4]. Even if the food-grade nutraceuticals enter the blood circulation, they are difficult to accumulate in the target organs and often cause damage to non-target organs.

      With the development of food nutrient delivery system technology (FNDS), especially promoted by the drug delivery technology, the utilization barrier of food-grade nutraceuticals has been gradually overcome, so that food-grade nutraceuticals are more and more effectively used. These FNDS can improve the solubility of food-grade nutraceuticals, enhance resistance to the environment, effectively transport food-grade nutraceuticals into the body, and target them to the organ[5]. However, the industrial application of FNDS faces many challenges. In addition, the future development direction of FNDS might affect the future development of the food industry (such as the functional beverage industry). Therefore, the challenges and future perspectives of FNDS are critically considered and summarized in this review as shown in Fig. 1, to promote the development and wide application of FNDS.

      Figure 1. 

      The challenges and future perspectives of food-grade nutraceutical delivery system[25,26].

    • The safety of FNDS, especially nano-delivery systems, has received attention from many researchers. This is because the composition, dose, size, morphology, hydrophobicity, and hydrophobicity aggregation of delivery systems may affect their toxicity[6]. In addition, under the complex environments of the digestive tract, the FNDS may react with the substances in the body or in the delivery system, affecting its metabolic fate, and eventually may have side effects on the body. Another point to consider is that the nano-FNDS, due to its small size can easily penetrate biological barriers such as intestinal mucus and tight junctions, enter the bloodstream, and eventually accumulate in different organs[7]. Long-term exposure to nanocarriers may result in cytotoxicity, fibrosis, oxidative stress, immune response, inflammation, and so on[7]. Inorganic nanocarriers, such as silicon dioxide, titanium dioxide, zinc oxide, etc., are easily accumulated in the heart, liver, and kidneys, etc., and when the amount is too much, reactive oxygen species can be generated to promote oxidative stress and damage organs[8]. Food-grade biomacromolecules (such as polysaccharides, proteins, and lipids) have good biocompatibility and degradability, and can be digested in the human gastrointestinal tract[9]. Therefore, delivery systems consisting of these biomacromolecules are generally considered safe. Only in some special cases, it may be toxic to the body. Some emulsion droplets contain indigestible interfacial layers or indigestible oil phase. Therefore, these indigestible bases prevent the enzymatic hydrolysis of the droplets. These unhydrolyzed emulsion droplets can potentially be absorbed in their intact forms. As a result, their final fate is not clear and they may have potential toxic effects on the human body[10]. Besides, it might be toxic that the carbohydrates or proteins (the building block of the nutrient delivery systems) are absorbed by their intact form[9]. For example, ovalbumin can be instantly absorbed from the distal intestine via the paracellular and clathrin- and receptor-mediated endocytic pathways. Eventually, this can lead to food allergies[10,11].

    • In the process of food manufacturing, transportation, storage, and marketing, FNDS is affected by environmental factors, such as temperature, humidity, light, and pH[3]. Food-grade nutraceuticals affected by these adverse environments may not only lead to the loss of precious nutraceuticals, but also greatly limit their industrial application. Additionally, the digestive environment also has a significant impact on the stability of the FNDS[1], as shown in Table 1. Although orally administered FNDS pass through the mouth very quickly, the structure of some substances may change significantly. After reaching the stomach, the FNDS may be degraded due to the highly acidic environment (pH 1.0~2.5) and the presence of various digestive enzymes, such as lipases, pepsins, and so on[12]. In the intestine, the presence of pancreatic enzymes (lipases, proteases, and amylases) and the intestinal environment with a pH of 6.0–7.0 can also cause the leakage of cargoes, so that food-grade nutraceuticals cannot reach the target organs[12]. It is worth noting that the structure of FNDS built with a single kind of protein or polysaccharide is poor in stability and is easily affected by the surrounding environment. Delivery systems are much more stable if built using two or multiple substances. For example, when whey protein and saccharide form a covalent complex, it can not only combine the advantages of the two biopolymers together, but also sometimes show new functional properties that the parent biopolymers do not have, with excellent delivery effects[13]. Bovine serum albumin (BSA) is an important building material of FNDS. Compared with BSA alone, saccharides-covalently modified BSA showed better binding strength and stability in the study of binding curcumin-carrying systems[14]. This is because the introduction of saccharides gives BSA better solubility and prevents BSA molecule aggregation. Moreover, since saccharides grafting promotes polarization of BSA molecules, the van der Waals forces and hydrogen bonds between curcumin and BSA are also enhanced[14]. In the study by Liu et al., the lactoferrin–chlorogenic acid conjugate was prepared via alkali treatment. Then, the conjugate was glycosylated with glucose by the Maillard reaction. Finally, the ternary conjugates (lactoferrin-chlorogenic acid-glucose) was obtained in this experiment. The ternary conjugates (lactoferrin-chlorogenic acid-glucose) were used to encapsulate β-carotene as a model biologically active macromolecule, and the ternary conjugates could enhance the physicochemical stability of β-carotene emulsions[15].

      Table 1.  Environmental conditions and functions of various parts of the human digestive tract[1].

      Digestive organs Residence time pH Enzyme Ionic concentration Function
      Mouth cavity 5~60 s 6.2~7.6 α-amylase 0.060 M Chewing breaks down food components and saliva acts as the lubricant. Amylase can catalyze the hydrolysis of starch into maltose, glucose, dextrin and so on.
      Stomach 30 min~4 h 1.0~2.5 Pepsin, lipase 0.152 M The stomach mainly produces protein enzymatic hydrolysis, lipase hydrolysis and other reactions, and the extremely low pH can effectively kill microorganisms.
      Small intestine 1~2 h 6.0~7.4 Lipase, pancreatin 0168~0.172 M The absorption of nutrients mainly occurs in the small intestine, including the release of endogenous active ingredients and the breakdown of food by endogenous enzymes.
      Colon 12~24 h 5~7 Microbiota-secreted enzyme 0.100 M The colon provides a natural environment for the growth of microbial flora, and nutrients in the colon mainly interacts with the colonized microbial flora.
    • In addition to protecting nutrients from destruction, another very important function of FNDS is to deliver cargo to target organs. However, in the process of transportation, due to the changes in the surrounding environment, the delivery system is easily damaged and it is difficult to reach the target location, as described previously. The mechanism of targeting mainly depends on the ability of FNDS to respond to changes in the microenvironment of the digestive tract. At present, some FNDS such as pH response, enzyme response, mucus penetration, and adhesion have been reported[16]. Generally, pH-sensitive FNDS contain groups that are sensitive to hydrogen ions and hydroxide, which can trigger force changes between intramolecular or intermolecular with pH changes, and then show changes in the properties of FNDS at the macro level. For example, the pH-sensitive hydrogels contain weakly acidic or weakly alkaline groups. Changes in pH can cause changes in the equilibrium state between the ionized and non-ionized types of these groups[17]. At low pH, the protonated acidic group interacts with the electronegative group in the hydrogels, and the hydrogel's pore size decreases and they are shrinking on a macro level. The nutraceuticals are not released at this time. With the increase of pH, the acidic groups dissociate, and the mutual attraction between polymer molecules weakens, resulting in the expansion of hydrogel pore size. Then, the cargoes will be released[18]. The FNDS responding to enzymes in the colon must be degraded and released by the catalysis of biological enzymes such as β-mannanase and glucanase, which are secreted by colon bacteria. The mucus penetration delivery system needs to be small and able to move through the mucus without restriction. For example, in the study of Li et al., they found that the pea albumin isolates hydrolyzed by enzymes trypsin was successfully used to prepare pea protein nanomicelles with gastrointestinal stability and strong permeability. Using capsaicin as a hydrophobic nutrient model, the nanocarrier system can effectively penetrate the mucus, increase the permeability of capsaicin by 2.5 times, and has excellent ability to overcome the mucus barrier[19].

    • With the improvement of living standards, human lifestyle is also changing. Single nutrients in daily life can no longer meet the growing health needs of human beings. Therefore, people pay more attention to the diversity and balance of nutrient intake. Developing the FNDS loaded with multiple nutraceuticals, that is, a multi-nutrient co-delivery system, is expected to become the future development direction. It has been reported that the multi-nutrient co-delivery system possesses several advantages such as achieving synergistic effects, formulating the proportion and dosage of different food-grade nutraceuticals, and controlling the release of food-grade nutraceuticals[1]. For example, liposomes are often used to co-encapsulate hydrophobic and hydrophilic substances because they have both a lipid bilayer and an aqueous compartments[1]. In the study by Krishna et al.[20], a droplet-based microfluidic device was used to synthesize the curcumin and quercetin co-encapsulated liposomes (made of phosphatidylcholine and cholesterol). The greatest encapsulation achieved for quercetin and curcumin was 36% ± 2.7% and 68% ± 9.2%, respectively. In vitro studies on FaDu oral carcinoma cells revealed that the co-delivery of quercetin and curcumin within liposomes synergistically enhanced their anticancer properties compared to liposomes with either quercetin or curcumin[20]. In addition, nanoparticles, emulsions, microcapsules, hydrogels, and related products have also been studied for nutraceutical co-delivery[21].

    • Most of the FNDS studied by previous researchers contain only one type of carrier, such as liposomes, emulsions, gels, etc. If two or more FNDS with different advantages are combined to develop a compound FNDS, they will have the advantages of different FNDS at the same time and may have a synergistic effect to achieve more efficient nutrient delivery. For example, emulsion gels, also known as gelled emulsions or emulgels, are complex colloidal materials in which both emulsion droplets and gels exist[22]. The gel materials of emulsion gels are usually polysaccharide (e.g., κ-carrageenan, alginate, and starch), and protein (e.g., gelatin and WPI), which can resist the destruction of the emulsion by stomach acid and protease. Due to mechanical action, chemical reaction, enzyme catalysis, and other processes, the emulsion will be released from the gel matrix, incorporated in the co-digested lipid droplets, interact with endogenous lipid surface-active compounds (mainly phospholipids and bile salts) promoting the formation of mixed micelles, and eventual transportation of the mixed micelles to the small intestinal epithelium[22]. In the study by Zhao et al., model hydrophilic (riboflavin) and hydrophobic (lycopene) ingredients were encapsulated in the internal water and oil phases of water-in-oleic acid in-water (W/O/W) emulsions, respectively. These emulsions were then dispersed into calcium alginate gels. Finally, it was found that the delivery system was able to stabilize in the simulated gastric fluid and release nutraceuticals in the simulated intestinal fluid. It not only improved the photostability of nutraceuticals but also improved the bioaccessibility of co-delivered nutraceuticals[23].

    • At present, most of the research on the release mechanism of FNDS has been carried out in vitro simulation conditions, rather than in animals or even humans[24]. A thorough understanding of the release mechanism of nutraceuticals and their final fate in the body will not only help to better design FNDS with more complete functions but also expand their application in the food industry. The common release mechanisms include desorption mechanisms (adsorption and desorption of food-grade nutraceuticals and FNDS), diffusion mechanisms (diffusion of nutraceuticals through the carrier matrix or capsule wall), dissolution mechanisms (dissolution of nutraceuticals in the release medium), and degradation mechanisms (release of nutraceuticals after the degradation of carrier materials, including swelling and corrosion of polymer materials) (Fig. 1)[25,26]. The release of nutraceuticals from FNDS mainly depends on the interaction of nutraceuticals, carrier, and release medium. If the binding force between the nutrient and the carrier is greater than the force between the carrier and the releasing medium, the nutrient release is mainly based on the degradation mechanism, and the release rate is mainly controlled by the swelling and dissolution process of the carrier material[27]. On the contrary, if the nutrient release mechanism is mainly diffusion, the release rate is controlled by the nutrient migration and diffusion process. When the nutrient is uploaded to the carrier in the form of adsorption, the drug is released through the process of desorption. After the nutraceuticals arrive in the intestine intact and are successfully released, it is still unclear whether they can enter the bloodstream to reach the targeted organs[26]. There are four ways for carriers and nutraceuticals to pass through the intestinal mucosal barrier. First, hydrophobic carriers mainly pass through the intestinal mucosa through the transcellular pathway; second, hydrophilic carriers cannot pass through the cell membrane and must first be transported through the cell bypass (but are limited by tight junction). The third is receptor-mediated nutrient uptake through intestinal mucosal channels. The fourth is the efflux pump on the intestinal mucosa to expel nutraceuticals through the cell membrane[28]. Li et al. found that nanotubes loaded with mangiferin could be prepared by self-assembly of hydrolyzed α-lactalbumin peptide fragments. The nanotubes were found to instantly and reversibly open the tight junctions between cells, facilitating the transport of nutraceuticals into the bloodstream[29].

    • FNDS can improve the solubility of food-grade nutraceuticals, enhance resistance to the environment, effectively transport food-grade nutraceuticals into the body and target specific organs. However, the current safety assessment of FNDS is not enough, and more extensive toxicological tests should be conducted in the future to ensure the safe use of FNDS. To protect food-grade nutraceuticals from destruction, developing FNDS that can resist harsh environments remains a thorny problem. An important function of FNDS is targeted delivery. However, the current oral FNDS have poor targeting in the body, especially to achieve targeting of internal organs or specific cells. In the future, the development direction of FNDS might be to develop multi-nutrient co-delivery systems to play the synergistic effect of food-grade nutraceuticals. Designing novel FNDS can combine the advantages of different delivery systems, such as the stability of the gel and the ability of liposomes to simultaneously load hydrophilic and hydrophobic food-grade nutraceuticals. In addition, attention should also be paid to the mechanism by which nutraceuticals are released from FNDS and the final fate of nutraceuticals so that the nutraceuticals can fully exert their effects. There is no doubt that the industrial application of FNDS is still a long way off, and there is still the need for further exploration in the future.

    • The authors confirm contribution to the paper as follows: writing - original draft, writing - review and editing, funding acquisition: Zhang Y; conceptualization: Wang Y, Xue Y; software: Wang Y, Zhang K; investigation: Zhang K; visualization: Lin X; formal analysis: Xue Y; validation: Zhang Z; methodology: Lin X, Zhang Z. All authors reviewed the results and approved the final version of the manuscript.

    • Data supporting this work is available within the article.

      • This study is supported by the Chinese Universities Scientific Fund (2024TC177).

      • The authors declare that they have no conflict of interest.

      • Copyright: © 2024 by the author(s). Published by Maximum Academic Press on behalf of Nanjing Agricultural University. This article is an open access article distributed under Creative Commons Attribution License (CC BY 4.0), visit https://creativecommons.org/licenses/by/4.0/.
    Figure (1)  Table (1) References (29)
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    Zhang Y, Wang Y, Zhang K, Lin X, Xue Y, et al. 2024. Out of the box thinking: challenges and future perspectives for food-grade nutraceutical delivery systems. Food Materials Research 4: e027 doi: 10.48130/fmr-0024-0022
    Zhang Y, Wang Y, Zhang K, Lin X, Xue Y, et al. 2024. Out of the box thinking: challenges and future perspectives for food-grade nutraceutical delivery systems. Food Materials Research 4: e027 doi: 10.48130/fmr-0024-0022

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