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Microbial transformation of anti-cancer steroid exemestane and cytotoxicity of its metabolites against cancer cell lines

Elias Baydoun1*, Marium Bibi2, Muhammad Asif Iqbal2, Atia-tul Wahab3, Dina Farran1, Colon Smith1, Samina A Sattar2, Atta-ur Rahman23 and M Iqbal Choudhary234*

Author Affiliations

1 American University of Beirut, Beirut, 1107 2020, Lebanon

2 H. E. J. Research Institute of Chemistry, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, 75270, Pakistan

3 Dr. Panjwani Center for Molecular Medicine and Drug Research, International Center for Chemical and Biological Sciences, University of Karachi, Karachi, 75270, Pakistan

4 Department of Biochemistry, Faculty of Science, King Abdulaziz University, Jeddah, 21412, Saudi Arabia

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Chemistry Central Journal 2013, 7:57  doi:10.1186/1752-153X-7-57

Published: 27 March 2013



Microbial transformation of steroids has been extensively used for the synthesis of steroidal drugs, that often yield novel analogues, not easy to obtain by chemical synthesis. We report here fungal transformation of a synthetic steroidal drug, exemestane, used for the treatment of breast cancer and function through inhibition of aromatase enzyme.


Microbial transformation of anti-cancer steroid, exemestane (1), was investigated by using two filamentous fungi. Incubation of 1 with fungi Macrophomina phaseolina, and Fusarium lini afforded three new, 11α-hydroxy-6-methylene-androsta-1, 4-diene-3,17-dione (2), 16β, 17β-dihydroxy-6-methylene-androsta-1, 4-diene-3-one (3), and 17β-hydroxy-6-methylene-androsta-1, 4-diene-3, 16-dione (4), and one known metabolites, 17β-hydroxy-6-methylene-androsta-1, 4-diene-3-one (5). Their structures were deduced spectroscopically. Compared to 1 (steroidal aromatase inactivator), the transformed metabolites were also evaluated for cytotoxic activity by using a cell viability assay against cancer cell lines (HeLa and PC3). Metabolite 2 was found to be moderately active against both the cell lines.


Biotransformation of exemestane (1) provides an efficient method for the synthesis of new analogues of 1. The metabolites were obtained as a result of reduction of double bond and hydroxylation. The transformed product 2 exhibited a moderate activity against cancer cell lines (HeLa and PC3). These transformed products can be studied for their potential as drug candidates.

Steroid; Exemestane; Anti-cancer activity; Cancer cell lines (HeLa; PC3); Fusarium lini; Macrophomina phaseolina; Microbial transformation

Graphical abstract