7-Hydroxyguanine, a novel antimetabolite from a strain of Streptomyces purpurascens. I. Taxonomy of producing organism, fermentation, isolation and biological activity.

Strain A-347, an actinomycete isolated from a soil sample, was found to produce a new antimetabolite, 7-hydroxyguanine. The aerial mycelium formed spiral spore chains with spiny spore surface. The chemical composition of strain A-347 indicated that it was an actinomycete of cell wall Type I. From its morphological, cultural, physiological characteristics and direct comparison with the type culture, this strain was classified as Streptomyces purpurascens. 7-Hydroxyguanine was purified from the broth filtrate by ion exchange chromatography and crystallized from hot 2 M NH4OH. 7-Hydroxyguanine inhibited the growth of experimental tumors such as L1210 leukemia.