Koshikamide A2, a cytotoxic linear undecapeptide isolated from a marine sponge of Theonella sp.

Koshikamide A(2) (2) was isolated as a cytotoxic metabolite from a marine sponge of Theonella sp. Its structure was elucidated to be a linear undecapeptide by spectroscopic and chemical methods, together with enzymatic conversion to known koshikamide A(1) (1). The new peptide moderately inhibited the growth of P388 murine leukemia cells.