Clonostachysins A and B, New Anti-dinoflagellate Cyclic Peptides from a Marine-derived Fungus

The two new anti-dinoflagellates, clonostachysins A and B, were obtained from a marine sponge derived fungus Clonostachys rogersoniana strain HJK9. Their chemical structures were determined by spectroscopic studies as highly N-methylated cyclic peptides of the nine amino acids. The absolute stereochemistry was elucidated by the advanced Marfey's method. Both clonostachysins A and B exhibited a selectively inhibitory effect on a dinoflagellate Prorocentrum micans at 30 µM, but had no effect on other microalgae and bacteria even at 100 µM.