Complete assignments of 1H and 13C NMR spectroscopic data for three new stigmastane glycosides from Vernonia cumingiana

Three new steroidal saponins, Vernoniosides S1 (1), Vernoniosides S2 (2) and Vernoniosides S3 (3) were isolated from the stem of Vernonia cumingian. Their chemical structures were elucidated on the basis of MS, NMR spectroscopic and chemical analysis. Complete assignment of (1)H and (13)C NMR spectroscopic data were achieved by 1D and 2D NMR experiments (HMQC, HMBC, ROESY).