BEQUINOSTATIN-A AND BEQUINOSTATIN-B, NEW INHIBITORS OF GLUTATHIONE-S-TRANSFERASE, PRODUCED BY STREPTOMYCES SP MI384-DF12 - PRODUCTION, ISOLATION, STRUCTURE DETERMINATION AND BIOLOGICAL-ACTIVITIES

New benzo[a]naphthacenequinone metabolites, designated bequinostatins A and B, have been isolated from the culture broth of the benastatin-producing strain Streptomyces sp. MI384-DF12. The structures of bequinostatins A and B were determined by spectral analyses to be 5,6,8,13-tetrahydro-1,6,7,9,11-pentahydroxy-8,13-dioxo-3-pentylbenzo[a]naphthacene-2-carboxylic acid and 2-decarboxybequinostatin A, respectively. Bequinostatin A showed considerable inhibitory-activity against human pi class glutathione S-transferase (GST pi).