Sesquiterpene lactones from Eupatorium lasiophthalmum

2 An investigation of Eupatorium lasiophthalmum yielded fourteen sesquiterpene lactones (1-14) including one new epimer (7) and a revision of the reported stereochemistry of 2 is suggested. One known sesquiterpene (15) and one triterpene (16) with a novel skeleton were found. Two known flavonoids (17-18) were also isolated. Michael adducts were prepared out of 1, 4 and 5 and their reversibility studied. The isolates 1-5, 7, 9, 15 and a cysteine ester adduct (19) were subjected to biological test to determine cytotoxicity against five different breast cancer cell lines. The adduct 19 showed significantly less cytotoxic efficacy compared to the sesquiterpene lactones. The anti-inflammatory activity of 4 was evaluated on LP