BIOPROSPECTING STUDIES ON SARCOCOCCA CORIACEA (HOOK. F.) OF NEPALESE ORIGIN

Abstract

Although fluorine is the most abundant halogen in the Earth’s crust, fluorine containing natural products are extremely rare in nature. This is due to the special properties of fluorine such as: a) it is found in highly insoluble form, therefore it has less bioavailability, b) it has very high heat of hydration due to which it is a poor nucleophile in aqueous solution, and also c) redox potential which is required for the oxidation of fluoride is higher than that generated by the reduction of hydrogen peroxide, thus fluorine cannot be incorporated into organic compounds via the haloperoxidase reaction. Due to these reasons, the mechanism by which C-F bond formation can take place has attracted a considerable scientific interest. Only 18 organofluorine containing natural products have been reported so far. All of them are primary metabolites and no fluorine containing secondary metabolite has been reported from any natural source. This Ph. D. study has led to an exciting discovery of a novel class of fluoropyrimidine substituted alkaloids from a medicinal plant, Sarcococca coriacea of Nepalese origin. Seven fluoropyrimidine containing steroidal alkaloids 1-7 and one novel fluoropyrimidine substituted ionone 8 have been obtained. This is the first time that fluorine containing secondary metabolites have been reported from any natural source, which has opened up a new avenue for further research in the chemistry of fluorine- containing secondary metabolites.