Phytochemical investigations on Uvaria narum (Annonaceae) and Elephantopus scaber (Compositae)

This thesis investigates two medicinal plants Uvaria narum (Annonaceae) and Elephantopus scaber (Compositae) belonging to the Indian flora. These investigations led to the isolation and characterization of ten new natural products in addition to several known ones.;Part I of this thesis describes a detailed investigation carried out on Uvaria narum. The chemistry of Uvaria narum was found to be very much different from the other investigated species of this genus except in the isolation of marker compounds such as glutinol, glutinone, taraxerol and benzylbenzoate. In addition to these known compounds, nine new compounds were characterized from the hexane and ethyl acetate extracts of the root bark.;Out of these, one is a sesquiterpene ketone with an unusual skeleton. The primary structure of this compound was elucidated with the help of 2D NMR studies.;The rest of the new compounds are Annonaceous acetogenins, a relatively new class of plant secondary metabolites which so far have been found only in certain Annonaceae species. Eight new acetogenins were characterized together with a known one. Among them, six compounds are having special structural features as different from the previously reported members of this class. Out of these, three compounds Uvariamicin-I,II and III are the first examples of a new structural subclass.;Part II of this thesis is a reinvestigation on Elephantopus scaber belonging to the Compositae family. This plant was previously investigated by many workers new sesquiterpene lactones belonging to the germacrane group were reported. With the hope of isolating more compounds, a reinvestigation was undertaken and only the roots were examined instead of the whole plant used in the previous studies. Phytochemical studies of the polar fractions of the root resulted in the isolation and characterization of four compounds which were isolated for the first time from this plant. Out of these, three compounds were sesquiterpene lactones belonging to the guaianolide group. One of these compounds was a new guaianolide glucoside. Part II of this thesis describes the isolation, characterization of these compounds from this plant.