Structure and bioactivity of triterpenoids from the stems of Schisandra sphenanthera

Two new triterpenoids, schisphendilactone A and B (1 and 2), together with three known triterpenoids, were isolated from the stems of Schisandra sphenanthera. Their structures were elucidated by spectroscopic methods, and the absolute configuration of 1 was determined by single-crystal X-ray diffraction. Compound 2 showed moderate inhibitory activity against SW480 cancer cell line, and compound 5 exhibited promising anti-HIV-1 activity with EC50 value of 0.52 mu g ml(-1) and therapeutic index value of 117.12.