A new alkaloid designated violatinctamine and four known metabolites were isolated from the tunicate Cystodytes cf. violatinctus collected in Kenya. Violatinctamine has a unique heterocyclic skeleton, which combines a benzothiazole unit and a dihydroisoquinoline unit. The structure of violatinctamine was elucidated by interpretation of MS results as well as 1D and 2D NMR spectra of the alkaloid and of its O,O'-dimethyl derivative. Analysis of the spectral information also implies that violatinctamine exists as a mixture of two tautomers-the imino-phenol and the amino quinone-methide. (C) 2004 Published by Elsevier Ltd.