Constituents of Paramichelia baillonii: a new antitumor germacranolide alkaloid.

Paramichelia baillonii has been used by the natives of Northern Thailand for medicinal purposes. Four components have been isolated from the bark of this plant and their structures determined by spectroscopic means. Three of the components had been reported previously: the germacranolide epoxides (--)-dihydroparthenolide [1] and (--)-parthenolide [2] and the oxoaporphinoid alkaloid liriodenine [4]. The fourth component is an unusual new germacranolide alkaloid which has been named (--)-bisparthenolidine [3] because it was presumably formed in the plant from ammonia and two molecules of parthenolide. Parthenolide was reported previously to possess anti-tumor activity, and in the present study we report on the significant activity of the new alkaloid 3 in the KB cell culture assay.