Studies on the Autoinhibitor Produced by Skeletonema costatum-II. Isolation and Identification of an Autoinhibitor Produced by Skeletonema costatum.

An autoinhibitor produced by Skeletonema costatum was extracted with ethyl acetate from the cultured medium. The extract dissolved in diluted aqueous NaOH was gel-filtered on Sephadex G-15 with water. The fractions which inhibited the growth of S. costatum were extracted with ethyl acetate, and the extracts were separated by preparative thin-layer chromatography on silica gel with acetone. The active portion was finally purified by high-performance liquid chromatography on ODS with aqueous acetonitrile. The autoinhibitor thus obtained was identified as 15-hydroxyeicosapentaenoic acid by spec-troscopic data of 13C NMR, 1H-1H COSY, and EIMS, as well as by comparison with an authentic sample.