Isolation and Structure of the Cytotoxic Cycloheptapeptide Phakellistatin 13

Abstract

A new cyclic heptapeptide phakellistatin 13 (1) had been isolated from the sponge Phakellia fusca Thiele, collected at Yongxing Island of China. Its structure was elucidated as cyclo-(Pro1-Trp-Leu-Thr-Pro2-Gly-Phe) on the basis of MS, UV, IR, and high-field NMR (600 MHz) analysis. The compound was significantly cytotoxic against the human hepatoma BEL-7404 cell line with an ED(50) < 10(-2) microg/mL.