Novel Biotransformations of 7-Ethoxycoumarin by Streptomyces griseus

Abstract

Biotransformation of 7-ethoxycoumarin by Streptomyces griseus resulted in the accumulation of two metabolites which were isolated and identified as 7-hydroxycoumarin and 7-hydroxy-6-methoxycoumarin. A novel series of biotransformation reactions is implicated in the conversion of the ethoxycoumarin substrate to these products, including O -deethylation, 6-hydroxylation to form a 6,7-dihydroxycoumarin catechol, and subsequent O -methylation. Either 7-hydroxycoumarin or 6,7-dihydroxycoumarin was biotransformed to 7-hydroxy-6-methoxycoumarin by S. griseus. Trace amounts of the isomeric 6-hydroxy-7-methoxycoumarin were detected when 6,7-dihydroxycoumarin was used as the substrate. Efforts to obtain a cell-free catechol- O -methyltransferase enzyme system from S. griseus were unsuccessful. However, [ methyl - 14 C]methionine was used with cultures of S. griseus to form 7-hydroxy-6-[ 14 C]methoxycoumarin.