New 5'-nucleotidase inhibitors, melanocidin A and melanocidin B. I. Taxonomy, fermentation, isolation and biological properties.

New 5'-nucleotidase inhibitors named melanocidins A and B were produced by Nocardioides sp. 1681 J. They were isolated from fermentation broth by trichloracetic acid extraction, ethanol precipitation and CM-cellulose and DEAE-cellulose column chromatography. They inhibited 5'-nucleotidase activity from snake venom but not from rat liver membrane at 200 micrograms/ml. They also show antitumor activity against melanoma B16.