Ravidomycin (AY-25,545), a new antitumor antibiotic.

A streptomycete was isolated from a Guatemala soil sample and found to inhibit Grampositive bacteria including mycobacteria. The antibiotic-producing microorganism was characterized, identified as a new species and named Streptomyces ravidus. The antibiotic principle was extracted with organic solvent from the mycelium, isolated in crystalline form and named ravidomycin. Ravidomycin is mainly active against Gram-positive bacteria including mycobacteria. It shows only weak activity against Gram-negative organisms and no activity against fungi. Ravidomycin exhibits potent antitumor activity against P388 lymphocytic leukemia, Colon 38 tumor and CD8F1 mammary tumor. Acute toxicity in mice is low.