Polycarpine dihydrochloride: A cytotoxic dimeric disulfide alkaloid from the Indian Ocean ascidian Polycarpa clavata

Polycarpine dihydrochloride (1); a new cytotoxic dimeric disulfide alkaloid, and four related compounds (2-5) have been isolated from extracts of the ascidian Polycarpa clavata (Hartman, 1919) collected in Western Australia. The structure of the new alkaloid was determined on the basis of comprehensive spectral studies and by interconversion to its free base and several degradation products. On silica chromatography, 1 was converted to the corresponding unstable free base (2) which decomposed, via cleavage of the disulfide bridge, into monomeric derivatives. Polycarpine dihydrochloride is cytotoxic against the human colon tumor cell line HCT-116 at 0.9 mu g/ml. Copyright (C) 1996 Elsevier Science Ltd