Characterization of tannic acid metabolites formed in vitro by rat liver microsomes and assay of their carcinogenicity by the microsomal degranulation technique

Tannic acid is converted to four metabolites on incubation with isolated rat liver microsomes. Bis-(3,4,5-trihydroxyphenyl)methanone (I); 3,4,6,7,9,10-hexahydroxy-2,11-epoxy-1,12-(epoxy-methano)-14H , 16H-benzob](1,4)benzodioxepino 3,2-g](1,4)benzodioxepin-14,16,17-trione (II) and 1,1,2-trimethyl-1-ethanyl-2-ylidene tris(3,4,5-trihydroxybenzoate) (III) were isolated from the post-microsomal supernatant of the incubate while 6,12,18,26,27,29,31,33-octahydroxy-22,22-dimethyl-2,8,14,20-tet raoxapentacyclo (22.2.2.2(4,7).2(10,13).2(16,19) tetratriaconta-4,6,10,12,16,18,24,26,27,29,31,33-dodecene-3, 9,15,21,23-pentone (IV) was found attached with the microsomal fraction. Metabolite (III) was found to be a potential carcinogen on the basis of microsomal degranulation technique.