The metabolism of the epoxide of testosterone by human placental microsomes

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