2-D NMR studies of geneoside, a novel pregnane pentaglycoside of 2-deoxy and 2, 6 dideoxy monosaccharides from ' Wattakaka lanceolata' .

Plants of Asclepiadaceae and Apocynaceae family are a rich source of pregnane and pregnane glycosides. They are found in nature either in free state or as their glycosides. They have shown antitumor, anticancer, and hypoglycaemic, antioxidant and antimicrobial activities. In our continued studies on the isolation of pregnane glycosides we have isolated a novel pregnane pentaglycoside comprised of 2-deoxy and 2, 6-dideoxy monosaccharides from Wattakaka lanceolata (Asclepiadaceae). The structure of the new glycoside, Geneoside was established as11 α , 12β- O -diacetyl-drevogenin-P-3- O - β - D -cymaropyaranosyl (1→4)- β - D -cymaropyranosyl (1→4) - β - D -Oleandropyranosyl (1→4)- β - D -digitalopyranosyl (1→4)- β - D -digitalopyranoside. The stereoscopic structure was established by chemical degradation, chemical transformation and recent physicochemical techniques viz 1 H,13 C, 2-D NMR (COSY, TOCSY, HSQC and HMBC) and Mass spectrometry.