Separacenes A–C, Cytotoxic Polyene Polyketides from the Marine Actinomycete, Streptomyces sp.

Abstract

During our search for new secondary metabolites with pharmaceutical potential, marine actinomycete strains, collected from Shinyang Beach in Jeju Island, were chemically analyzed by LC/MS. One of the marine actinomycetes strains, SNW10 (Streptomyces sp. based on 16S rDNA analysis), was revealed to produce unique tetraene / triene-bearing metabolites, which named separacenes A-C. The structures of the separacenes were determined by spectroscopic analysis of 1D and 2D NMR, MS and UV data. Separacene A possessing terminal olefinic double bond, conjugated tetraene, and two 1,2-diol groups, turned out to be a new 15-membered linear polyketide. The absolute configuration of separacene A was established by modified Moshers method. The structures of separacene B and C, which incorporate terminal olefinic methylene, tirene, and two 1,2-diol moieties, were also elucidated by spectroscopic analysis and chemical derivatization. Separacene A displayed cytotoxic activity against the HCT116 and A549 cancer cell line.