Biotransformation of AD and ADD using Nostoc muscorum

Abstract

The potential of microalgae for steroid transformation has been studied less than other microorganisms. They have been applied for the years in the treatment of environmental pollutions and preparation of nutrients. At the first time, Abul-Hajj and Qian indicated the conversion of androstendione (AD) to testosterone with eleven different strains of microalgae. Previtera’s group showed the transformations of progesterone and prednisolone in several microalgal cultures within four studies. In other investigations, steroid substrates were 5?-androstane-3, 17-dione, adrenosterone, androsta-1, 4-diene-3, 17-dione (ADD) and 17?-hydoxy-17?-methylandrosta-1, 4-dien-3-one. Hydrocortisone biotransformation using Nostoc muscorum was also reported with Tabatabie group. In this study, the ability of Nostoc muscorum, blue green algae, for biotransformation of AD and ADD were investigated. This potential has not been previously examined. The selected microalgae was isolated during a screening program from soil samples collected from paddy field of north of Iran. The fermentation media were included BG-11 medium together with AD or ADD 0.05%, separately, as steroid substrates. The experiment was illuminated continuously with fluorescent lamps at 40 µEm-2S-1, and incubated at a temperature of 25±2°C without shaking for ten days. The chloroform extract was loaded on silica gel plates with acetone/hexan (1:1) solvent system. The obtained fractions were further purified by re-chromatography, followed by crystallization. Then, the metabolites and unconverted substrates from each experiment were identified by melting points and spectral methods including 13C NMR, 1H NMR, FTIR and MS. The fermentation reaction of AD with Nostoc muscorum led to accumulation of testosterone in the broth medium. 1-Dehydrotestosterone was the product of ADD bioconversion in the microalgal culture. In both cases, the bioconversion characteristics observed were 17-carbonyl reduction. Thus, the microorganism represented to act selectively at the ketone group on the D-ring of both androstane like steroids.