ISOLATION AND STRUCTURE DETERMINATION OF NOVEL PHOSPHATIDYLINOSITOL TURNOVER INHIBITORS, PIERICIDIN-B(5) AND B(5)-N-OXIDE, FROM STREPTOMYCES SP

in the course of a screening program for inhibitors of epidermal growt h factor (EGF)-induced phosphatidylinositol turnover in human epidermo id carcinoma cell line A431, we discovered two novel compounds of the piericidin family from the culture broth and mycelia of a Streptomyces strain MJ288-OF3. We named them piericidin B5 and B5 N-oxide. By NMR and mass spectrometric analyses, the molecular formulas of piericidin B5 and B5 N-oxide were determined to be C27H41NO4 (MW 443) and C27H41N O5 (MW 459), respectively. Piericidin B5 and B5 N-oxide inhibited phos phatidylinositol turnover of A431 cells with IC50s of 10.0 mug/ml and 1.1 mug/ml, respectively.