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.
