Hemistepsins with cytotoxic activity from Hemisteptia lyrata

Two sesquiterpene lactones were isolated from Hemisteptia lyrata Bunge (Compositae). Their structures were elucidated by spectroscopic methods as recently known hemistepsin and the new 6-O-(2-methylpropenoyl)-3-hydroxy-4(15), 10(14), 11(13)-guaiatrien-12,8-olide. The two hemistepsin derivatives were examined for their in vitro cytotoxic activity against human cell lines such as UACC 62, HCT 15, UO-31, PC-3 and A549. Growth inhibitory property was determined by in vitro treatment of the respective cell lines using the sulforhodamine B assay (SRB). Both compounds exhibited significant cytotoxic activity (IC50 < 4.3 micrograms/ml) on all five human cell lines tested.