A new diketopiperazine from the gorgonian coral Menella kanisa.

Chemical investigation on the gorgonian Menella kanisa collected from Beibu Gulf led to the isolation of a new diketopiperazine, named menazepine A (1), as well as three known diketopiperazines, namely cyclo(4-hydroxyprolylleucyl) (2), cyclo(Pro-Leu) (3) and cyclo(4-hydroxyprolylphenylalanyl) (4). The structure of the new diketopiperazine was elucidated on the basis of extensive spectroscopic analysis and by comparing the data with those of related metabolites. Compounds 1-4 were also evaluated for brine shrimp lethality.