Microbiological hydroxylation of estradiol: formation of 2- and 4-hydroxyestradiol by Aspergillus alliaceus

Microorganisms known to hydroxylate alkaloids, amino acids, and aromatic substrates were examined for their potential to hydroxylate 17 beta-estradiol and estrone. Thin-layer chromatography of fermentation extracts revealed a wide range of steroid products. Aspergillus alliaceus (UI 315) was the only culture capable of producing good yields of catechol estrogens with 17 beta-estradiol. The organism also transformed estrone but not to catechol products. Analytical experiments with high-performance liquid chromatography revealed that A. alliaceus formed 4- and 2-hydroxyestradiol with yields of 45 and 16%, respectively. A preparative-scale incubation was conducted in 2 liters of medium containing 1 g of 17 beta-estradiol as substrate. 4-Hydroxyestradiol was isolated and identified by proton nuclear magnetic resonance and high-resolution mass spectrometry. Ascorbic acid was added to microbial reaction mixtures as an antioxidant to prevent the decomposition of unstable catechol estrogen metabolites. The microbial transformation of 17 beta-estradiol by A. alliaceus provides an efficient one-step method for the preparation of catechol estrogens.