Bequinostatins C and D, new inhibitors of glutathione S-transferase, produced by Streptomyces sp. MI384-DF12

Benastatins have been isolated as part of a program designed to find microorganism-produced inhibitors of glutathione S-transferase from Streptomyces sp. MI384-DF12. They were purified by chromatography of reversed-phase silica gel, silica gel and Capcell Pak C18 (HPLC) followed by solvent extraction and then isolated as yellow powders. Benastatins A and B have the molecular formulae, C30H28O7 and C30H30O7, respectively. They were competitive with 3, 4-dichloronitrobenzene as the substrate, and the inhibition constants (Ki) of benastatins A and B were 5.0 × 10-6 and 3.7 × 10-6, respectively.