[Studies on antitumor activity of valinomicin].

Streptomyces sp. No. 22 strain, which was freshly isolated from a soil sample froms Nossap Cape and considered to be closely related to Streptomyces alboviridis showed strong antitumor activity against L1210 culture established cells when incubated in glucose-starch bouillon under the usual conditions. An anti-L1210 substance was found at an early stage of mycelium development and in the filtrate. When extracted with organic solvents from the whole broth and purified with silica gel column chromatography, the substance was obtained as crystallized colorless platelets and chemically identified as the antifungal agent Valinomycin. The antitumor activity of Valinomycin was reported by A. J. Repta in 1981 as a result of the NCI screening test and was found to be effective against P-388 tumor. In an antitumor activity test carried out in our laboratory in vitro or/and in vivo, No. 22 substance was also revealed to be effective against P-388 tumor in host mice, KB cells, and so on.