Cytotoxic evaluation of natural and synthetic callipeltins: a revision of cytotoxicity of callipeltin B

The cytotoxic evaluation of natural and synthetic callipeltins is described. Cyclic depsipeptide callipeltin B and linear peptides callipeltins E and M synthesized by us showed no cytotoxic activity. In contrast, natural callipeltin B purified from Callipelta sp. showed CC50 = 130 mu M against Hela cells. We found that purified callipeltin B included the contamination of callipeltins C and H at a ratio of approximately 15%. These results suggested that the cytotoxicity of natural callipeltin B was derived from callipeltins C and H.