7-oxodioscin, a new spirostan steroid glycoside from the rhizomes of Dioscorea nipponica

摘要

Nine glycosides of spirostan (1-7) and furostan (8 and 9) type steroids including a new compound, 7-oxodioscin (1), were isolated from the rhizomes of Dioscorea nipponica. The structure of 1 was established as (25R)-3β-O- [(α-L-rhamnopyranosyl-(1→4)-O-[α-L-rhamnopyranosyl-(1→2)] -β-Dglucopyranosyl) oxy]spirost-5-en-7-one by extensive spectroscopic techniques including HRESI-TOFMS, 1D and 2D NMR, and chemical methods. Known compounds were elucidated as dioseptemloside G (2), (25R)-dracaenoside G (3), orbiculatoside B (4), dioscin (5), progenin III (6), gracillin (7), (3β,22α,25R)-26-(β-D-glucopyranosyloxy)-22-methoxyfurost-5-en-3- yl O-[α-L-rhamnopyranosyl-(1→4)]-β-D-glucopyranoside (8), and methylprotodioscin (9).