Phytochemical investigation of Hypericum xylosteifolium (Hypericaceae), a Caucasus endemic species

The small mountainous country of Georgia lies within the Caucasus Biodiversity Hotspot, which has ca. 2750 endemic vascular plant species. High interest in assessing the biodiversity and conservation status of selected native plant species of Georgia, particularly those with potential or existing economic value, exists [1]. As part of a collaborative research project, an IUCN Red List assessment of the endemic species Hypericum xylosteifolium (taxonomic section Inodora) for Georgia and the northern Caucasus region was conducted and distribution maps based on historical information and recent field studies prepared. Correspondingly, due to the medicinal value and interesting phytochemistry of related Hypericum species, a preliminary phytochemical examination of cultivated material from this species was conducted. Dichloromethane extracts of the fruits were analyzed by chromatographic means (TLC, OC, HPLC) and structure elucidation of isolated pure compounds was performed using data from NMR and MS. This research resulted in the isolation of several γ-pyrone derivatives, including hyperenone A (1) and B (2), which have been previously reported from H. mysurense (section Ascyreia) (2). Interesting aspects of this observed chemical convergence are discussed.

Fig.1: Gamma-pyrone derivatives from Hypericum xylosteifolium

Acknowledgements: This research was supported in part by a grant from the Austrian Science Foundation (FWF, Project T345). Sincere thanks to Helen Long, Chris Clennett and David Hardman for assisting with the collection of plant material at the Royal Botanic Gardens, Wakehurst Place, England.

References: 1. IUCN, WHO, WWF (1993). Guidelines on the Conservation of Medicinal Plants, IUCN, Gland, Switzerland, 50p.

2. Kikuchi et al. (1985) Chem. Pharm. Bull. 33: 1969–74.