Fungal transformation and T-cell proliferation inhibitory activity of melengestrol acetate and its metabolite

•Biotransformation of melengestrol acetate (1) was carried out with C. blakesleeana.•The above transformation yielded a new major metabolite 2.•Single crystal X-ray structures of 1 and 2 are reported for the first time.•Immmunosuppressant effect of 1 and 2 was evaluated by T--cell proliferation assay.

Biotransformation of melengestrol acetate (MGA, 17α-acetoxy-6-methyl-16-methylenepregna-4,6-diene-3,20-dione) (1) was investigated for the first time by using fungal cultures. Incubation of compound 1 with Cunninghamella blakesleeana yielded a new major metabolite, 17α-acetoxy-11β-hydroxy-6-methyl-16-methylenepregna-4,6-diene-3,20-dione (2). The metabolite 2 was purified by using HPLC, followed by characterization through 1H- and 13C-NMR and other spectroscopic techniques. Single crystal X-ray diffraction analysis was used to deduce the three dimensional structures of melengestrol acetate (1) and metabolite 2 for the first time. T-cell proliferation assay was employed to evaluate the immunosuppressant effect of compounds 1 and 2 with IC50 = 0.5 ± 0.07 and 0.6 ± 0.08 μg/mL, respectively. The results indicated that these compounds possess sixfold potent T-cell proliferation inhibitory activity as compared to the standard prednisolone (IC50 < 3.1 μg/mL). Both compounds were found to be non-toxic in a 3T3 (mouse fibroblast) cell-based cytotoxicity assay. This discovery of potent anti-inflammatory activity of compounds 1 and 2 can lead the way to develop new immunosuppressant compounds for clinical application.

Graphical abstractBiotransformation of melengestrol acetate (1) with Cunninghamella blakesleeana.Figure optionsDownload full-size imageDownload as PowerPoint slide