Microbial transformation of terreusinone, an ultraviolet-A (UV-A) protecting dipyrroloquinone, by Streptomyces sp.

Biotransformation study was conducted on the marine dipyrroloquinone, terreusinone (1) isolated from the marine-derived fungus Aspergillus terreus. Preparative-scale fermentation of terreusinone with Streptomyces sp. has resulted in the isolation of a new oxidized metabolite, terreusinol (2). The structure was elucidated as 2-[(1R)-1-hydroxyisobutyl]-6-[(1R)-1,2-dihydroxyisobutyl]-1H,5H-pyrrolo[2,3-b]indole-4,8-dione (2) on the basis of physicochemical evidence. Terreusinol (2) showed an ultraviolet-A (UV-A) (320-390 nm) protecting activity with ED(50) values of 150 microM, which is more active than oxybenzone (ED(50), 350 microM) currently being used as sunscreen.