Polyoxypregnane steroids with an open-chain sugar moiety from Marsdenia tenacissima and their chemoresistance reversal activity.

ABSTRACT

A polyoxypregnane aglycone, 12ß-O-acetyl-11α-O-isobutyryltenacigenin B, and four polyoxypregnane glycosides with a pachybionic acid ester moiety, 12ß-O-acetyl-3-O-(6-deoxy-3-O-methyl-ß-D-allopyranosyl-(1→4)-ß-D-oleandronyl)-11α-O-isobutyryltenacigenin B, 12ß-O-acetyl-3-O-(6-deoxy-3-O-methyl-ß-D-allopyranosyl-(1→4)-ß-D-oleandronyl)-11α-O-tigloyltenacigenin B, 12ß-O-acetyl-3-O-(6-deoxy-3-O-methyl-ß-D-allopyranosyl-(1→4)-ß-D-oleandronyl)-11α-O-2-methylbutyryltenacigenin B, and 12ß-O-acetyl-3-O-(ß-D-glucopyranosyl-(1→4)-6-deoxy-3-O-methyl-ß-D-allopyranosyl-(1→4)-D-oleandronyl)-11α-O-tigloyltenacigenin B, were isolated from the canes of Marsdenia tenacissima, together with a disaccharide derivative. Their structures were elucidated by extensive spectroscopic analysis, and the absolute configurations were further determined by X-ray crystallographic analysis. With the exception of the disaccharide derivative, all five compounds are unusual naturally occurring polyoxypregnane glycosides bearing an open-chain sugar moiety. Two of these exhibit a wide spectrum of chemoresistance reversal activity, and potential mechanisms were studied accordingly.