The metabolism of the epoxide of testosterone by human placental microsomes.

Although 19-hydroxy-4beta,5-oxido-5beta-androstane-3,17 dione (2a) is converted to estradiol-17beta by human placental microsomes, the incubation of 17beta-hydroxy-4beta,5-oxido-5beta-androstan-3-one (2b) under the same conditions produces only metabolites which are more polar than 17beta-estradiol. The metabolites have been isolated and identified as 3alpha-hydroxy-4beta,5-oxido-5beta-androstan-17-one (4a), 4beta,5-oxido-5beta-androstane-3beta, 17beta-diol (5a) and 4beta,5-oxido-5beta-androstane-3alpha,17beta-diol (6a). These results indicate that functionalization at C-19 is a prerequisite for the biological aromatization of such androgen epoxides.