Figures (7)  Tables (2)

    • Figure 1. 

      Key chemical constituents of Hypericum perforatum. Different colors represent chemical classes: Naphthodianthrones, Phloroglucinol Derivatives, Xanthones, Phenylpropanoids, Proanthocyanidins, Catechins, Biflavonoids, Flavonoids.

    • Figure 2. 

      Hypericin accumulation in Hypericum perforatum organs: (a) bud, (b) stamens, (c) leaf. Hypericin (1) is accumulated in Dark Glands (DGs) of the aerial parts of the plants like (a) sepals and petals, (b) stamens, and (c) leaves.

    • Figure 3. 

      Key points to hypericin biosynthesis research.

    • Figure 4. 

      Hypericin biosynthesis as presented by Rizzo et al.[17]. In bold: enzymes involved in reactions' catalysis. Abbreviations: OKS: Oktaketide Synthase, PKC: Polyketide Cyclase, TER: Thioesterase, POCP: Phenolic Oxidative Coupling Protein, BBE: Berberine Bridge Enzyme, 2-ODD: 2-oxoglutarate and Fe(II)-dependent oxygenase, UGT: UDP-glucosyltransferase.

    • Figure 5. 

      Hyperforin accumulation in Hypericum perforatum organs: (a) fruit, (b) leaf. Hyperforin (2) is accumulated in formations like vittae (Vi) and vesicles (Ve) on the (a) fruit capsule, and in the (b) Pale Glands (PGs) of the leaves.

    • Figure 6. 

      Biosynthesis of Hyperforin (2) and its homologue Adhyperforin according to Wu et al.[37,38]. In bold: enzymes involved in reactions' catalysis and prenyl-groups. Abbreviations: BCAT: branched-chain amino acid aminotransferase, BCKDH: branched-chain alpha-keto acid dehydrogenase, CCL: CoA ligase, PKS: Polyketide synthase, PT: Prenyltransferase, DMAPP: dimethylallyl-diphosphate, GPP: geranyl-diphosphate.

    • Figure 7. 

      Formation of the xanthone skeleton[65−67]. In bold: enzymes involved in reactions catalysis. Abbreviations: BPS: benzophenone synthase, CYP81AA1 (TXS1) and CYP81AA2 (TXS2): bifunctional cytochrome P450 enzymes, X6H: xanthone 6-hydroxylase.

    • Class Substance
      Naphodianthrones (precussors and derivatives) Hypericin
      Pseudohypericin
      Protohypericin
      Protopseudohypericin
      Skyrin
      Skyrin-6-O-ß-glucopyranoside
      Emodin
      Emodin dianthrone
      Phloroglucinol derivatives Hyperforin
      Adhyperforin
      Hyperfirin
      Adhyperfirin
      Furohyperforin
      Xanthones 1,6-dihydroxy-5-methoxy-4′,5′-dihydro-4′,4′,5′-trimethylfurano-(2′,3′:3,4)-xanthone
      4,6-dihydroxy-2,3-dimethoxyxanthone
      cis-kielcorin
      Magniferin
      1,3,6,7-tetrahydroxyxanthone
      Phenylpropanoids Caffeic acid
      Chlorogenic acid
      Flavonoids Quercetin
      Quercitrin
      Hyperoside
      Rutin
      Biflavonoids I3,II8-Biapigenin
      Amentoflavone
      Proanthocyanidins Procyanidin B2
      Catechins Catechin
      Epicatechin

      Table 1. 

      Key chemical constituents of Hypericum perforatum[1,14−18].

    • Genes involved in hypericin biosynthesis Genes involved in hyperforin biosynthesis
      Confirmed by the functional characterization of the respective protein HpPKS2[34] BCKDH[37]
      CLL[37]
      PKS[37]
      PT1-4[38]
      Hypothetical based on transcriptional data POCP1-4[35]
      TER[17]
      BBE[17]
      Rejected by experiments HYP1[36] HpPKS1[39]

      Table 2. 

      Genes suggested to participate in hypericin and hyperforin biosynthesis.