Stylissatins B-D, cycloheptapeptides from the marine sponge Stylissa massa

The NMR and LC-MS guided chromatographic fractionation of the CH2Cl2 extract of the sponge Stylissa massa resulted in the isolation of three new cycloheptapeptides, namely stylissatins B-D (1-3), together with ten known cyclopeptides. The structures of stylissatins B-D were established by comprehensive analysis of 2D NMR (COSY, TOCSY, HMQC, HMBC, and ROESY) in association with the ESI-MS/MS fragmentation. The L-configuration of the amino acid residues was determined based on the Marfey's method. Stylissatin B (1) exhibited the inhibitory effects against a panel of human tumor cell lines including HCT-116, HepG2, BGC-823, NCI-H1650, A2780, and MCF7 with the IC50 values ranging from 2.4 to 9.8 M. (C) 2016 Elsevier Ltd. All rights reserved.