Abstract
The active medicinal constituents in Hypericum perforatum, used to treat depression and skin irritation, include flavonoids and xanthones. The carbon skeletons of these compounds are formed by chalcone synthase (CHS) and benzophenone synthase (BPS), respectively. Polyclonal antisera were raised against the polyketide synthases from Hypericum androsaemum and their IgG fractions were isolated. Immunoblotting and immunotitration were used to test the IgGs for crossreactivity and monospecificity in H. perforatum leaf protein extract. Immunofluorescence localization revealed that both CHS and BPS are located in the mesophyll. The maximum fluorescence levels were observed in approx. 0.5 and 1 cm long leaves, respectively. The fluorescence intensity observed for CHS significantly exceeded that for BPS. Using histochemical staining, flavonoids were detected in the mesophyll, indicating that the sites of biosynthesis and accumulation coincide. Our results help understand the biosynthesis and underlying regulation of active H. perforatum constituents.
Highlights
Medications containing extracts from the flowering upper parts of the medicinal plant Hypericum perforatum
We focus on the localization of benzophenone synthase (BPS) and chalcone synthase (CHS)
In the medicinal plant H. perforatum, the major active metabolites are formed by polyketide synthases, two of which are BPS and CHS
Summary
Medications containing extracts from the flowering upper parts of the medicinal plant Hypericum perforatum (St. John’s wort; Hypericaceae) are used for the treatment of mild to moderate depressions as well as skin irritations and infected wounds (Linde et al, 2008; Wölfle et al, 2014). Due to the additive and synergistic effects of the ingredients, the entire extract is commonly used for therapy. The major active constituents involve hyperforins, hypericins, flavonoids, and xanthones (Beerhues, 2011). All these four classes of compounds are polyketide derivatives. Variations in the starter molecule, the number of extender units and the mode of cyclization result in the formation of an amazing array of PKS products
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