Biotransformation of (20S)-20-hydroxymethylpregna-1,4-dien-3-one by four filamentous fungi

Microbial transformation of oral contraceptive ethisterone by Aspergillus niger and Cunninghamella blakesleeana

Ethisterone (17α-ethynyl-17β-hydroxyandrost-4-en-3-one) (1) is a synthetic steroidal estrogen. It is extensively used as an oral contraceptive. The current study involves the structural transformation of ethisterone (1) by Aspergillus niger, and Cunninghamella blakesleeana. Fermentation of 1 with C. blakesleeana afforded two new polar metabolites, 17α-ethynyl-6β,15β,17β-trihydroxyandrost-4-en-3-one, and 17α-ethynyl-7β,15β,17β-trihydroxyandrost-4-en-3-one, while transformation of ethisterone with A. niger yielded a new metabolite, 17α-ethynyl-6α,17β-dihydroxyandrost-4-en-3-one, along with a known metabolite, 17α-ethynyl-11α,17β-dihydroxyandrost-4-en-3-one. Modern spectroscopic techniques were used to characterize the structures of all transformed products.

Microbial biotransformation of bioactive and clinically useful steroids and some salient features of steroids and biotransformation

Steroids are perhaps one of the most widely used group of drugs in present day. Beside the established utilization as immunosuppressive, anti-inflammatory, anti-rheumatic, progestational, diuretic, sedative, anabolic and contraceptive agents, recent applications of steroid compounds include the treatment of some forms of cancer, osteoporosis, HIV infections and treatment of declared AIDS. Steroids isolated are often available in minute amounts. So biotransformation of natural products provides a powerful means in solving supply problems in clinical trials and marketing of the drug for obtaining natural products in bulk amounts. If the structure is complex, it is often an impossible task to isolate enough of the natural products for clinical trials. The microbial biotransformation of steroids yielded several novel metabolites, exhibiting different activities. The metabolites produced from pregnenolone acetate by Cunning hamella elegans and Rhizopus stolonifer were screened against tyrosinase and cholinesterase showed significant inhibitory activities than the parent compound. Diosgenin and its transformed sarsasapogenin were screened for their acetyl cholinesterase and butyryl cholinesterase inhibitory activities. Sarsasapogenin was screened for phytotoxicity, and was found to be more active than the parent compound. Diosgenin, prednisone and their derivatives were screened for their anti-leishmanial activity. All derivatives were found to be more active than the parent compound. The biotransformation of steroids have been reviewed to a little extent. This review focuses on the biotransformation and functions of selected steroids, the classification, advantages and agents of enzymatic biotransformation and examines the potential role of new enzymatically transformed steroids and their derivatives in the chemoprevention and treatment of other diseases. tyrosinase and cholinesterase inhibitory activities, severe asthma, rheumatic disorders, renal disorders and diseases of inflammatory bowel, skin, gastrointestinal tract.

Bio-Catalytic Structural Transformation of Anti-cancer Steroid, Drostanolone Enanthate with Cephalosporium aphidicola and Fusarium lini, and Cytotoxic Potential Evaluation of Its Metabolites against Certain Cancer Cell Lines

In search of selective and effective anti-cancer agents, eight metabolites of anti-cancer steroid, drostanolone enanthate (1), were synthesized via microbial biotransformation. Enzymes such as reductase, oxidase, dehydrogenase, and hydrolase from Cephalosporium aphidicola, and Fusarium lini were likely involved in the biotransformation of 1 into new metabolites at pH 7.0 and 26°C, yielding five new metabolites, 2α-methyl-3α,14α,17β-trihydroxy-5α-androstane (2), 2α-methyl-7α-hydroxy-5α-androstan-3,17-dione (3), 2-methylandrosta-11α-hydroxy-1, 4-diene-3,17-dione (6), 2-methylandrosta-14α-hydroxy-1,4-diene-3,17-dione (7), and 2-methyl-5α-androsta-7α-hydroxy-1-ene-3,17-dione (8), along with three known metabolites, 2α-methyl-3α,17β-dihydroxy-5α-androstane (4), 2-methylandrosta-1, 4-diene-3,17-dione (5), and 2α-methyl-5α-androsta-17β-hydroxy-3-one (9), on the basis of NMR, and HREI-MS data, and single-crystal X-ray diffraction techniques. Interestingly, C. aphidicola and F. lini were able to catalyze hydroxylation only at alpha positions of 1. Compounds 1–9 showed a varying degree of cytotoxicity against HeLa (human cervical carcinoma), PC3 (human prostate carcinoma), H460 (human lung cancer), and HCT116 (human colon cancer) cancer cell lines. Interestingly, metabolites 4 (IC₅₀ = 49.5 ± 2.2 μM), 5 (IC₅₀ = 39.8 ± 1.5 μM), 6 (IC₅₀ = 40.7 ± 0.9 μM), 7 (IC₅₀ = 43.9 ± 2.4 μM), 8 (IC₅₀ = 19.6 ± 1.4 μM), and 9 (IC₅₀ = 25.1 ± 1.6 μM) were found to be more active against HeLa cancer cell line than the substrate 1 (IC₅₀ = 54.7 ± 1.6 μM). Similarly, metabolites 2 (IC₅₀ = 84.6 ± 6.4 μM), 3 (IC₅₀ = 68.1 ± 1.2 μM), 4 (IC₅₀ = 60.4 ± 0.9 μM), 5 (IC₅₀ = 84.0 ± 3.1 μM), 6 (IC₅₀ = 58.4 ± 1.6 μM), 7 (IC₅₀ = 59.1 ± 2.6 μM), 8 (IC₅₀ = 51.8 ± 3.4 μM), and 9 (IC₅₀ = 57.8 ± 3.2 μM) were identified as more active against PC-3 cancer cell line than the substrate 1 (IC₅₀ = 96.2 ± 3.0 μM). Metabolite 9 (IC₅₀ = 2.8 ± 0.2 μM) also showed potent anticancer activity against HCT116 cancer cell line than the substrate 1 (IC₅₀ = 3.1 ± 3.2 μM). In addition, compounds 1–7 showed no cytotoxicity against 3T3 normal cell line, while compounds 8 (IC₅₀ = 74.6 ± 3.7 μM), and 9 (IC₅₀ = 62.1 ± 1.2 μM) were found to be weakly cytotoxic.

Biotransformation of a potent anabolic steroid, mibolerone, with Cunninghamella blakesleeana, C. echinulata, and Macrophomina phaseolina, and biological activity evaluation of its metabolites

Seven metabolites were obtained from the microbial transformation of anabolic-androgenic steroid mibolerone (1) with Cunninghamella blakesleeana, C. echinulata, and Macrophomina phaseolina. Their structures were determined as 10β,17β-dihydroxy-7α,17α-dimethylestr-4-en-3-one (2), 6β,17β-dihydroxy-7α,17α-dimethylestr-4-en-3-one (3), 6β,10β,17β-trihydroxy-7α,17α-dimethylestr-4-en-3-one (4), 11β,17β-dihydroxy-(20-hydroxymethyl)-7α,17α-dimethylestr-4-en-3-one (5), 1α,17β-dihydroxy-7α,17α-dimethylestr-4-en-3-one (6), 1α,11β,17β-trihydroxy-7α,17α-dimethylestr-4-en-3-one (7), and 11β,17β-dihydroxy-7α,17α-dimethylestr-4-en-3-one (8), on the basis of spectroscopic studies. All metabolites, except 8, were identified as new compounds. This study indicates that C. blakesleeana, and C. echinulata are able to catalyze hydroxylation at allylic positions, while M. phaseolina can catalyze hydroxylation of CH₂ and CH₃ groups of substrate 1. Mibolerone (1) was found to be a moderate inhibitor of β-glucuronidase enzyme (IC₅₀ = 42.98 ± 1.24 μM) during random biological screening, while its metabolites 2–4, and 8 were found to be inactive. Mibolerone (1) was also found to be significantly active against Leishmania major promastigotes (IC₅₀ = 29.64 ± 0.88 μM). Its transformed products 3 (IC₅₀ = 79.09 ± 0.06 μM), and 8 (IC₅₀ = 70.09 ± 0.05 μM) showed a weak leishmanicidal activity, while 2 and 4 were found to be inactive. In addition, substrate 1 (IC₅₀ = 35.7 ± 4.46 μM), and its metabolite 8 (IC₅₀ = 34.16 ± 5.3 μM) exhibited potent cytotoxicity against HeLa cancer cell line (human cervical carcinoma). Metabolite 2 (IC₅₀ = 46.5 ± 5.4 μM) also showed a significant cytotoxicity, while 3 (IC₅₀ = 107.8 ± 4.0 μM) and 4 (IC₅₀ = 152.5 ± 2.15 μM) showed weak cytotoxicity against HeLa cancer cell line. Compound 1 (IC₅₀ = 46.3 ± 11.7 μM), and its transformed products 2 (IC₅₀ = 43.3 ± 7.7 μM), 3 (IC₅₀ = 65.6 ± 2.5 μM), and 4 (IC₅₀ = 89.4 ± 2.7 μM) were also found to be moderately toxic to 3T3 cell line (mouse fibroblast). Interestingly, metabolite 8 showed no cytotoxicity against 3T3 cell line. Compounds 1–4, and 8 were also evaluated for inhibition of tyrosinase, carbonic anhydrase, and α-glucosidase enzymes, and all were found to be inactive.

Biocatalyst-mediated production of 11,15-dihydroxy derivatives of androst-1,4-dien-3,17-dione

Hydroxylation of steroids at various positions is a powerful tool for the production of valuable pharmaceutical ingredients and precursors. Our paper reported the synchronous dihydroxylation of an efficient strain, i.e., Colletotrichum lini AS3.4486, at two points. C. lini AS3.4486 was selected from 10 strains; this strain can catalyze the dihydroxylation of androst-1,4-dien-3,17-dione at C-11α and C-15α positions. Transformation of ADD(I) by C. lini AS3.4486 produced metabolites II-IV. The structures of these compounds were elucidated by liquid chromatography-mass spectrometry (LC-MS), Fourier Transform infrared spectroscopy (FTIR), nuclear magnetic resonance (NMR), and X-ray as 15-hydroxyandrost-1,4-dien-3,17-dione (15α-OH-ADD; II), 11,15-dihydroxyandrost-1,4-dien-3,17-dione (11,15-diOH-ADD; III), and 15,17β-dihy-droxyandrost-1,4-dien-3-one (15-OH-BD; BD is the abbreviation of boldenone; IV). III, as a novel compound, was reported for the first time. The course of conversion and mechanism about dihydroxylation reaction was also investigated. On the basis of time course analysis of hydroxylation, I underwent regioselective hydroxylation at 15 position and was subsequently converted to III and IV. Enzyme inhibition analysis showed that 11- and 15-hydroxylations were catalyzed by different hydroxylases. The effect of substrate concentration on I transformation was also determined. Results showed that the optimum concentration of I was 20 g/L, and the yield of III was up to 18.8 g/L.

Microbial-catalysed derivatization of anti-cancer drug exemestane and cytotoxicity of resulting metabolites against human breast adenocarcinoma cell line (MCF-7) in vitro

Structural transformation of anticancer drug exemestane (1) with fungi Cunninghamella blakesleeana (ATCC 8688A), Curvularia lunata (ATCC 12017), Aspergillus niger (ATCC 10549), and Gibberella fujikuroi (ATCC 10704) yielded eleven metabolites 2-12, in which 2 and 8 were identified as new. Their structures were characterized as 6-methylene-5α-androstane-3β,16β,17β-triol (2), 17β-hydroxy-6-methyleneandrosta-4-ene-3-one (3), 6α-spiroxirandrost-4-ene-3,17-dione (4), 6-methyleneandrosta-4-ene-3,17-dione (5), 6β,17β-dihydroxyandrost-4-en-3-one (6), 17β-hydroxy-6α-spiroxirandrost-1,4-diene-3-one (7), 17β-hydroxy-6α-hydroxymethylandrosta-1,4-dien-3-one (8), 6α-hydroxymethylandrosta-1,4-diene-3,17-dione (9), 17β-hydroxy-6-methyleneandrosta-1,4-diene-3,16-dione (10), 6α-hydroxy-4-androstene-3,17-dione (11), and 6α-hydroxymethylandrost-4-ene-3,17-dione (12). Substrate 1, and its transformed products were evaluated for their cytotoxicity against breast cancer cell line (MCF-7). Compound 3 was found to be moderately active with an IC₅₀ of 33.43±4.01μM, in comparison to the standard anti-cancer drug, doxorubicin (IC₅₀=0.92±0.1μM).

Biotransformation of 6-dehydroprogesterone with Aspergillus niger and Gibberella fujikuroi

Microbial transformation of 6-dehydroprogesterone (1) with Aspergillus niger yielded three new metabolites, including 6β-chloro-7α,11α-dihydroxypregna-4-ene-3,20-dione (2), 7α-chloro-6β,11α-dihydroxypregna-4-ene-3,20-dione (3), and 6α,7α-epoxy-11α-hydroxypregna-4-ene-3,20-dione (4), and two known metabolites; 6α,7α-epoxypregna-4-ene-3,20-dione (5), and 11α-hydroxypregna-4,6-diene-3,20-dione (6). Compounds 2, and 3 contain chlorohydrin moiety at C-6, and C-7, respectively. The biotransformation of 1 with Gibberella fujikuroi yielded a known compound, 11α,17β-dihydroxyandrosta-4,6-dien-3-one (7).

Aspergillus niger-mediated biotransformation of methenolone enanthate, and immunomodulatory activity of its transformed products

Two fungal cultures Aspergillus niger and Cunninghamella blakesleeana were used for the biotransformation of methenolone enanthate (1). Biotransformation with A. niger led to the synthesis of three new (2-4), and three known (5-7) metabolites, while fermentation with C. blakesleeana yielded metabolite 6. Substrate 1 and the resulting metabolites were evaluated for their immunomodulatory activities. Substrate 1 was found to be inactive, while metabolites 2 and 3 showed a potent inhibition of ROS generation by whole blood (IC50=8.60 and 7.05μg/mL), as well as from isolated polymorphonuclear leukocytes (PMNs) (IC50=14.0 and 4.70μg/mL), respectively. Moreover, compound 3 (34.21%) moderately inhibited the production of TNF-α, whereas 2 (88.63%) showed a potent inhibition of TNF-α produced by the THP-1 cells. These activities indicated immunomodulatory potential of compounds 2 and 3. All products were found to be non-toxic to 3T3 mouse fibroblast cells.

New Anti-Inflammatory Metabolites by Microbial Transformation of Medrysone

Microbial transformation of the anti-inflammatory steroid medrysone (1) was carried out for the first time with the filamentous fungi Cunninghamella blakesleeana (ATCC 8688a), Neurospora crassa (ATCC 18419), and Rhizopus stolonifer (TSY 0471). The objective was to evaluate the anti-inflammatory potential of the substrate (1) and its metabolites. This yielded seven new metabolites, 14α-hydroxy-6α-methylpregn-4-ene-3,11,20-trione (2), 6β-hydroxy-6α-methylpregn-4-ene-3,11,20-trione (3), 15β-hydroxy-6α-methylpregn-4-ene-3,11,20-trione (4), 6β,17α-dihydroxy-6α-methylpregn-4-ene-3,11,20-trione (5), 6β,20S-dihydroxy-6α-methylpregn-4-ene-3,11-dione (6), 11β,16β-dihydroxy-6α-methylpregn-4-ene-3,11-dione (7), and 15β,20R-dihydroxy-6α-methylpregn-4-ene-3,11-dione (8). Single-crystal X-ray diffraction technique unambiguously established the structures of the metabolites 2, 4, 6, and 8. Fungal transformation of 1 yielded oxidation at the C-6β, -11β, -14α, -15β, -16β positions. Various cellular anti-inflammatory assays, including inhibition of phagocyte oxidative burst, T-cell proliferation, and cytokine were performed. Among all the tested compounds, metabolite 6 (IC₅₀= 30.3 μg/mL) moderately inhibited the reactive oxygen species (ROS) produced from zymosan-induced human whole blood cells. Compounds 1, 4, 5, 7, and 8 strongly inhibited the proliferation of T-cells with IC₅₀ values between <0.2–10.4 μg/mL. Compound 7 was found to be the most potent inhibitor (IC₅₀ < 0.2 μg/mL), whereas compounds 2, 3, and 6 showed moderate levels of inhibition (IC₅₀ = 14.6–20.0 μg/mL). Compounds 1, and 7 also inhibited the production of pro-inflammatory cytokine TNF-α. All these compounds were found to be non-toxic to 3T3 cells (mouse fibroblast), and also showed no activity when tested against HeLa (human epithelial carcinoma), or against PC3 (prostate cancer) cancer cell lines.

Microbial transformation of danazol with Cunninghamella blakesleeana and anti-cancer activity of danazol and its transformed products

Biotransformation of danazol (1) (17β-hydroxy-17α-pregna-2,4-dien-20-yno-[2,3-d]-isoxazole) with Cunninghamella blakesleeana yielded three new metabolites 2-4 and a known metabolite 5. These metabolites were identified as 14β,17β-dihydroxy-2-(hydroxymethyl)-17α-pregn-4-en-20-yn-3-one (2), 1α,17β-dihydroxy-17α-pregna-2,4-dien-20-yno-[2,3-d]-isoxazole (3), 6β,17β-dihydroxy-17α-pregna-2,4-dien-20-yno-[2,3-d]-isoxazole (4), and 17β-hydroxy-2-(hydroxymethyl)-17α-pregn-1,4-dien-20-yn-3-one (5). Danazol (1) and its derivatives were evaluated against cervical cancer cell line (HeLa). Compound 1 showed a potent cytotoxicity with IC50=0.283±0.013 μM, as compared to doxorubicin (IC50=0.506±0.015 μM), where compound 3 was also found to be significantly active with IC50=13.427±0.819 μM.

Biotransformation of testosterone and testosterone heptanoate by four filamentous fungi

The microbial transformations of testosterone and testosterone heptanoate by four fungi: Absidia griseolla var. igachii PTCC 5260, Acremonium chrysogenu PTCC 5271, Fusarium fujikuroi PTCC 5144, and Fusarium solani complex PTCC 5285 were investigated for the first time. Incubation of testosterone heptanoate with F. fujikuroi and F. solani yielded three metabolites, which were isolated and characterized as testosterone, androst-4-ene-3,17-dione, and 6β-hydroxy testosterone. 6β-Hydroxy testosterone was the major metabolite obtained from testosterone heptanoate biotransformation by two fungal species. A. griseolla and A. chrysogenu produced 14α-hydroxy testosterone as major metabolite, together with testosterone and 6β-hydroxy testosterone in lower yields. The biotransformation of testosterone by F. fujikuroi and A. griseolla was also investigated in order to examine the influence of the ester group on the course of transformation. Androst-4-ene-3,17-dione was only identified in the biotransformation of testosterone by F. fujikuroi. The same product was observed in incubation of testosterone by A. griseolla, together with 14α-hydroxy testosterone in very low yield. Furthermore, time course study was also carried out in order to examine the formation of metabolites as a function of time, which was determined by HPLC. The structures of compounds were determined by their comprehensive spectroscopic analysis and comparison with literature data.

Microbial biotransformation of beclomethasone dipropionate by Aspergillus niger

In the present research, the steroidal anti-asthmatic drug beclomethasone dipropionate was subjected to microbial biotransformation by Aspergillus niger. Beclomethasone dipropionate was transformed into various metabolites first time from microbial transformation. New drug metabolites produced can act as new potential drug molecules and can replace the old drugs in terms of safety, efficacy, and least resistance. They were purified by preparative thin layer chromatography technique, and their structures were elucidated using modern spectroscopic techniques, such as 13C NMR, 1H NMR, HMQC, HMQC, COSY, and NOESY, and mass spectrometry, such as EI-MS. Four metabolites were purified: (i) beclomethasone 17-monopropionate, (ii) beclomethasone 21-monopropionate, (iii) beclomethasone, and (iv) 9beta,11beta-epoxy-17,21-dihydroxy-16beta-methylpregna-1,4-diene-3,20-dione 21-propionate.

Microbial transformation of nandrolone with Cunninghamella echinulata and Cunninghamella blakesleeana and evaluation of leishmaniacidal activity of transformed products

Therapeutic potential of nandrolone and its derivatives against leishmaniasis has been studied. A number of derivatives of nandrolone (1) were synthesized through biotransformation. Microbial transformation of nandrolone (1) with Cunninghamella echinulata and Cunninghamella blakesleeana yielded three new metabolites, 10β,12β,17β-trihydroxy-19-nor-4-androsten-3-one (2), 10β,16α,17β-trihydroxy-19-nor-4-androsten-3-one (3), and 6β,10β,17β-trihydroxy-19-nor-4-androsten-3-one (4), along with four known metabolites, 10β,17β-dihydroxy-19-nor-4-androsten-3-one (5), 6β,17β-dihydroxy-19-nor-4-androsten-3-one (6) 10β-hydroxy-19-nor-4-androsten-3,17-dione (7) and 16β,17β-dihydroxy-19-nor-4-androsten-3-one (8). Compounds 1-8 were evaluated for their anti-leishmanial activity. Compounds 1 and 8 showed a significant activity in vitro against Leishmania major. The leishmanicidal potential of compounds 1-8 (IC50=32.0±0.5, >100, 77.39±5.52, 70.90±1.16, 54.94±1.01, 80.23±3.39, 61.12±1.39 and 29.55±1.14 μM, respectively) can form the basis for the development of effective therapies against the protozoal tropical disease leishmaniasis.

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

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 (1)H- and (13)C-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±0.08μg/mL, respectively. The results indicated that these compounds possess sixfold potent T-cell proliferation inhibitory activity as compared to the standard prednisolone (IC50<3.1μg/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.

Biotransformation of androgenic steroid mesterolone with Cunninghamella blakesleeana and Macrophomina phaseolina

Fermentation of mesterolone (1) with Cunninghamella blakesleeana yielded four new metabolites, 1α-methyl-1β,11β,17β-trihydroxy-5α-androstan-3-one (2), 1α-methyl-7α,11β,17β-trihydroxy-5α-androstan-3-one (3), 1α-methyl-1β,6α,17β-trihydroxy-5α-androstan-3-one (4) and 1α-methyl-1β,11α,17β-trihydroxy-5α-androstan-3-one (5), along with three known metabolites, 1α-methyl-11α,17β-dihydroxy-5α-androstan-3-one (6), 1α-methyl-6α,17β-dihydroxy-5α-androstan-3-one (7) and 1α-methyl-7α,17β-dihydroxy-5α-androstan-3-one (8). Biotransformation of 1 with Macrophomina phaseolina also yielded a new metabolite, 1α-methyl, 17β-hydroxy-5α-androstan-3,6-dione (9). The isolated metabolites were subjected to various in vitro biological assays, such as anti-cancer, inhibition of α-glucosidase, and phosphodiesterase-5 enzymes and oxidative brust. However, no significant results were observed. This is the first report of biotransformation of 1 with C. blakesleeana and M. phaseolina.

Biotransformation of 17α-ethynyl substituted steroidal drugs with microbial and plant cell cultures: a review

Structural modification of steroids through whole-cell biocatalysis is an invaluable procedure for the production of active pharmaceutical ingredients (APIs) and key intermediates. Modifications could be carried out with regio- and stereospecificity at positions hardly available for chemical agents. Much attention has been focused recently on the biotransformation of 17α-ethynyl substituted steroidal drugs using fungi, bacteria and plant cell cultures in order to obtained novel biologically active compounds with diverse structure features. Present article includes studies on biotransformation on 17α-ethynyl substituted steroidal drugs using microorganisms and plant cell cultures. Various experimental and structural elucidation methods used in biotransformational processes are also highlighted.

New metabolites from fungal biotransformation of an oral contraceptive agent: methyloestrenolone

Fungal cell cultures were used for the first time for the biotransformation of methyloestrenolone (1), an oral contraceptive. Fermentation of 1 with Macrophomina phaseolina, Aspergillus niger, Gibberella fujikuroi, and Cunninghamella echinulata produced eleven metabolites 2-12, six of which 2-5, 11 and 12 were found to be new. These metabolites were resulted from the hydroxylation at C-1, C-2, C-6, C-10, C-11, and C-17α-CH3, as well as aromatization of ring A of the steroidal skeleton of substrate 1. The transformed products were identified as 17α-methyl-6β,17β-dihydroxyestr-4-en-3-one (2), 17α-(hydroxymethyl)-11β,17β-dihydroxyestr-4-en-3-one (3), 17α-methyl-2α,11β,17β-trihydroxyestr-4-en-3-one (4), 17α-methyl-1β,17β-dihydroxyestr-4-en-3-one (5), 17α-methyl-11α,17β-dihydroxyestr-4-en-3-one (6), 17α-methyl-11β,17β-dihydroxyestr-4-en-3-one (7), 17α-methyl-10β,17β-dihydroxyestr-4-en-3-one (8), 17α-(hydroxymethyl)-17β-hydroxyestr-4-en-3-one (9), 17α-methylestr-1,3,5(10)-trien-3,17β-diol (10), 17α-methyl-3,17β-dihydroxyestr-1,3,5(10)-trien-6-one (11), and 17α-methyl-6β,10β,17β-trihydroxyestr-4-en-3-one (12).

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

Background

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.

Results

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.

Conclusions

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.

Synthesis of some potent immunomodulatory and anti-inflammatory metabolites by fungal transformation of anabolic steroid oxymetholone

BACKGROUND

Biotransformation of organic compounds by using microbial whole cells provides an efficient approach to obtain novel analogues which are often difficult to synthesize chemically. In this manuscript, we report for the first time the microbial transformation of a synthetic anabolic steroidal drug, oxymetholone, by fungal cell cultures.

RESULTS

Incubation of oxymetholone (1) with Macrophomina phaseolina, Aspergillus niger, Rhizopus stolonifer, and Fusarium lini produced 17β-hydroxy-2-(hydroxy-methyl)-17α-methyl-5α-androstan-1-en-3-one (2), 2α,17α-di(hydroxyl-methyl)-5α-androstan-3β,17β-diol (3), 17α-methyl-5α-androstan-2α,3β,17β-triol (4), 17β-hydroxy-2-(hydroxymethyl)-17α-methyl-androst-1,4-dien-3-one (5), 17β-hydroxy-2α-(hydroxy-methyl)-17α-methyl-5α-androstan-3-one (6), and 2α-(hydroxymethyl)-17α-methyl-5α-androstan-3β-17β-diol (7). Their structures were deduced by spectral analyses, as well as single-crystal X-ray diffraction studies. Compounds 2-5 were identified as the new metabolites of 1. The immunomodulatory, and anti-inflammatory activities and cytotoxicity of compounds 1-7 were evaluated by observing their effects on T-cell proliferation, reactive oxygen species (ROS) production, and normal cell growth in MTT assays, respectively. These compounds showed immunosuppressant effect in the T-cell proliferation assay with IC50 values between 31.2 to 2.7 μg/mL, while the IC50 values for ROS inhibition, representing anti-inflammatory effect, were in the range of 25.6 to 2.0 μg/mL. All the compounds were found to be non-toxic in a cell-based cytotoxicity assay.

CONCLUSION

Microbial transformation of oxymetholone (1) provides an efficient method for structural transformation of 1. The transformed products were obtained as a result of de novo stereoselective reduction of the enone system, isomerization of double bond, insertion of double bond and hydroxylation. The transformed products, which showed significant immunosuppressant and anti-inflammatory activities, can be further studied for their potential as novel drugs.

Biotransformations utilizing β-oxidation cycle reactions in the synthesis of natural compounds and medicines

β-Oxidation cycle reactions, which are key stages in the metabolism of fatty acids in eucaryotic cells and in processes with a significant role in the degradation of acids used by microbes as a carbon source, have also found application in biotransformations. One of the major advantages of biotransformations based on the β-oxidation cycle is the possibility to transform a substrate in a series of reactions catalyzed by a number of enzymes. It allows the use of sterols as a substrate base in the production of natural steroid compounds and their analogues. This route also leads to biologically active compounds of therapeutic significance. Transformations of natural substrates via β-oxidation are the core part of the synthetic routes of natural flavors used as food additives. Stereoselectivity of the enzymes catalyzing the stages of dehydrogenation and addition of a water molecule to the double bond also finds application in the synthesis of chiral biologically active compounds, including medicines. Recent advances in genetic, metabolic engineering, methods for the enhancement of bioprocess productivity and the selectivity of target reactions are also described.

Microbial steroid transformations: current state and prospects

Studies of steroid modifications catalyzed by microbial whole cells represent a well-established research area in white biotechnology. Still, advances over the last decade in genetic and metabolic engineering, whole-cell biocatalysis in non-conventional media, and process monitoring raised research in this field to a new level. This review summarizes the data on microbial steroid conversion obtained since 2003. The key reactions of structural steroid functionalization by microorganisms are highlighted including sterol side-chain degradation, hydroxylation at various positions of the steroid core, and redox reactions. We also describe methods for enhancement of bioprocess productivity, selectivity of target reactions, and application of microbial transformations for production of valuable pharmaceutical ingredients and precursors. Challenges and prospects of whole-cell biocatalysis applications in steroid industry are discussed.