Thiazostatin A and thiazostatin B. new antioxidants produced by Streptomyces tolurosus.

During screening for antioxidative substances, which are expected to be useful for chemotherapy of arteriosclerosis and ischemia, we have isolated new potent substances thiazostatins A and B from a culture of an actinomycete, Streptomyces tolurosus 1368-MT1, which was isolated from a soil sample collected at a field in Yamaguchi-city, Japan.Thiazostatin was formerly called AG551} and its producing organism has been deposited at the Fermentation Research Institute, Agency of Industrial Science and Technology, Japan, with an accession No. of FERMP-9144.The fermentation, isolation, structure determination and biological properties ofthiazostatin are described in the present communication.The antioxidant activity was measured by inhibitory effect against erythrocyte hemolysis caused by a radical producing agent, 2,2/-azobis-