PRODUCTION, PURIFICATION, AND ANTIFUNGAL ACTIVITY OF THE ANTIBIOTIC NUCLEOSIDE, TUBERCIDIN, PRODUCED BY STREPTOMYCES-VIOLACEONIGER

Three antibiotic substances strongly inhibitory to Phytophthora capsic i or Magnaporthe grisea were isolated from the broth culture of Strept omyces violaceoniger strain A50. A butanol-solubIe mixture of antibiot ics from the broth were partially purified by XAD-2 column chromatogra phy. The XAD-2 eluates inhibited the mycelial growth of P. capsici and M. grisea and the development of Phytophthora blight on pepper (Capsi cum annuum L.) plants. The antibiotics were separated by silica gel co lumn chromatography and then purified on a Sephadex LH-20 column to yi eld three peaks of antifungal activity: SF1A, SF1B, and SF2A. The pure antibiotic SF2A was further purified by preparative HPLC and identifi ed as the pyrrolo[2,3-d]pyrimidine nucleoside tubercidin based on the UV, H-1, and C-13 NMR spectral data and other chemical evidence. The a ntibiotic SF2A and authentic tubercidin showed a high antifungal activ ity against the plant pathogenic fungi P. capsici, Botryosphaeria doth idea, and Rhizoctonia solani.