This work is based on the chemical and biological studies of the two folkloric medicinal plants Caralluma tuberculata and C. edulis. This thesis is divided into three parts.
Part I includes general introduction, botanical description, ethnopharmacognosy, pharmacological and toxic manifestation, chemical constituents, review on pregnanes and biosynthesis of pregnane molecules of Caralluma plants.
Part II consists of the results of structural characterization and elucidation final conclusion and discussion on the isolated compounds and their biological activities.
Part III records investigations on the laboratory experiments on pregnanes, terpenes and flavonoids type of compounds isolated and their biological evaluation.
The present work describes the isolation and structure elucidation of seven new pregnane glycosides namely caratuberside A, B, C, D, E, F and G from Caralluma tuberculata and compared with the pregnanes obtained from Caralluma edulis. The structures of caratuberside A-G were determined by chemical and spectroscopic means. These pregnane types of glycosides have riot been reported earlier from these plants.
In addition to these, two sterols: β-sitosterol and its glycoside; five terpenes: taraxastero1,lupeol. β-amyrin, α-amyrin, α-amyrin acetate and α-amyrin cinnamate; three flavonoids: luteolin-4 -O-β-D-glucopyranosyl-(21)-α-D-rhamnopyranoside, kaempefrol-7-0-β-D-glycopyranosyl-(21)-α-L-rhamnopyranoside and kaempefrol-3-0-β-D glucopyranosyl- (61 )-α-L-rhamnoside have also been isolated and identified.
The schematic representation of the extraction and isolation of compounds as well as their structures and physico-chemical data are given on following pages.
Biological activity evaluation of the ethanolic and aqueous extracts of the plant as well as caratubersides was also carried out. The ethanolic extract showed various degrees of antibacterial activity. Brine shrimp (LD50) bioassay of ethanolic and ethyl acetate extracts showed. toxicity whereas aqueous extract was found to be non-toxic. The aqueous extract of Caralluma tuberculata was found to possess hypoglycaemic activity in alloxan treated rats. However, 3H-ouabain binding assay with Caratubersides A-C, and an inhibitory effect of ethanolic extract of C. edulis on adrenaline induced platelet aggregation essentially exhibited no response.