Isolation and structure of phakellistatin 14 from the Western Pacific marine sponge Phakellia sp.

A new cycloheptapeptide, phakellistatin 14, was isolated in 8.8 x 10(-7)% yield from Phakellia sp., a marine sponge from Chuuk, Federated States of Micronesia. The structure (1), cyclo-Phe-beta-OMe-Asp-Ala-Met(SO)-Ala-Ile-Pro, was elucidated by 1D and 2D NMR spectral analyses augmented by HRFABMS. The chirality of each amino acid unit was determined to be S using chiral HPLC methods. Phakellistatin 14 showed cancer cell growth inhibitory activity (ED(50) 5 microg/mL) against the murine lymphocytic leukemia P388 cell line.