PHYTOCHEMICAL AND PHARMACOLOGICAL STUDIES ON SOME MEDICINAL PLANTS OF SRI LANKA

Abstract

Attached

This thesis covers the phytochemical studies and some biological studies of two medicinal plants belonging to the family Apocynaceae namely, Ae~Lonia mac~ophyeea and Ae~Lonia ~choea~i~. The second part of this thesis describes the estimation of vasicine content in AdhaLoda va~ica and its seasonal variation in the plant. The second chapter describes the taxonomy and chemical characteristics of the genus Ae~Lonia. The biosynthesis of indole alkaloids including the formation of strictosidine and the plausible biogenetic pathways of some Ae~Lonia alkaloids are given in detail. General methods of extraction of alkaloids that have been used so far, their advantages, disadvantages and more advanced and improved techniques are discussed in the fifth chapter. According to the pharmacological reports on Ae~ionia alkaloids,it is evident that the two plants we have studied have significant medicinal value. In the first part of the eigth chapter, the method of extraction, fractionation and isolation of alkaloids of A. mac~ophyiia and A. ~choia~i~ described in detail including the precautions undertaken to isolate alkaloids in their genuine form. Structures of twelve alkaloids have been elucidated from these two plants. One of which is a new alkaloid, 19-hydroxyvincamajine. In these studies we have found that local A. mac~ophyiea is different from the same species found in other countries due to the presence of talcarpine, vincamajine,19- hydroxyvincamajine, vincorine and cabucraline. Talcarpine and picraline deacetyl are reported for the first time from the genus Ae~tonia. These studies give us significant evidences for chemotaxonomic relationships among different species of At~tonia and some other genera such as 7age~naemontana, St~ychno~, Pieioca~pa and A~pido~p6~ma. The effect of alkaloidal extracts of these two plants (leaf and stem bark) on alternative and classical pathways of human complement was tested in vitro. These findings suggest that these two plant alkaloids can be used as immunomodulating agents.