Biosynthesis of estrogens. Estr-5(10)-ene-3,17-dione: isolation, metabolism and mechanistic implications

The 16- 2H 2 title compound 5b constituted a significant amount of the non-aromatic metabolites recovered from incubations of 3,17-dioxo-[16,16,19- 2H 3]androst-4-en-19-al 1 with placental aromatase. For the evaluation of the role of compound 5b in the elaboration of estrogens, its transformations at pH 6.5 and 7.2 in the presence and absence of microsomal placental aromatase were investigated. In the presence of the aromatase at pH 6.5, estrogens (6.8%), products of isomerization of the double bond [Δ 5(10)→Δ 4] and products of reduction of the carbonyl groups were formed. When the incubation was carried out at pH 7.2, products similar to those obtained above were isolated but in different yields. Noticeably more estrogens (22.7%) and less of the reduced products were formed. Additionally, at pH 7.2, 10β-hydroxy-[16,16- 2H 2]estr-4-ene-3,17-dione 4a was obtained. In the absence of the aromatase, which was replaced with bovine albumin at both pH 6.5 and 7.2, [16,16- 2H 2]estr-4-ene-3,17-dione 3a and its 10β-hydroxy derivative 4a were formed in large amounts and were the only products detected. The ramifications of our observations in the context of estrogen biosynthesis are discussed.