Two new stilbenoids from Bletilla striata

Two new stilbenoids bletilol D (1) and bletilol E (2), together with five known compounds were isolated from Bletilla striata. Three of them (3, 4, and 7) were obtained from this genus for the first time. Their structures were elucidated by spectroscopic methods and comparing with data reported in literatures. The cytotoxic activities of compounds 1-7 against MCF-7 (human breast cancer) and A549 (human lung carcinoma) cell lines were evaluated by MTT assay. Compound 2 showed weak cytotoxicity against MCF-7 and A549 cell lines with IC50 values of 36.32 +/- 1.17 and 36.48 +/- 1.12M, respectively, and 5 exhibited weak cytotoxicity against MCF-7 cell line with IC50 value of 57.09 +/- 2.03M.