Microbial transformation of azacarbazoles. VII. Antitumor properties of benzo-alpha-iso-carbolines formed by Kitasatosporia setae strain from corresponding benzo-alpha-carbolines.

2,3-Benzo-alpha-carboline, 7,8-benzo-alpha-carboline and their 4-methyl derivatives were subjected to microbial conversion yielding corresponding benzo-alpha-iso-carbolines. All obtained products showed significant antimicrobial and cytotoxic properties. ID50 values were found to be at range 0.01-0.001 microM/ml, regarding in vitro KB tumor cells system data. It has been found that introduction of methyl group at para-position to the nitrogen of pyridine nucleus strongly increases cytotoxic and microbial activity of benzo-alpha-iso-carbolines. Apparently it has been indicated that antitumor activity of benzo-alpha-iso-carbolines is strongly dependent on shape and size of the molecule. Of all the compounds tested only 2,3-benzo-1,4-dimethyl-alpha-iso-carboline increases life span of leukemia P388 bearing mice up to 160%.