C21 steroidal glycosides from Cynanchum taihangense

Two new C21 steroidal glycosides, cynataihosides E (1) and F (2), together with a known one, sublanceoside H2 (3), were isolated from Cynanchum taihangense. The aglycone of cynataihoside F (2) was also a new compound. Their structures were elucidated on the basis of NMR spectroscopic data, HR-ESI-MS analysis, and chemical evidence. Their cytotoxic activities against three human tumor cell lines (HL-60, THP1, and Caco2) were reported.