Biotransformation of tolbutamide to 4′-hydroxytolbutamide by the fungus Cunninghamella blakesleeana
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The hypoglycemic drug tolbutamide is commonly used as a probe drug to evaluate CYP2C9 enzyme activity in terms of production of 4′-hydroxytolbutamide. In the present study, an initial screening of seven filamentous fungi was carried out to identify which was most competent to transform tolbutamide into 4′-hydroxytolbutamide. From this screening, the fungus Cunninghamella blakesleeana AS 3.910 was selected as a suitable bioconverter. At a concentration of 1.2 mg ml−1, the growing fungus transformed 95.0% of tolbutamide into 4′-hydroxytolbutamide in 96 h. With resting culture, the yield could reach 91.7% and exceeded 91.0% even when the tolbutamide concentration was increased to 4.0 mg ml−1. On scale-up to 3 l buffer containing 12.0 g tolbutamide, 90% of tolbutamide was transformed into 4′-hydroxytolbutamide in 96 h. Work-up of the broth by column chromatography and recrystallization yielded 6.5 g (53.9% recovered) of 4′-hydroxytolbutamide with a purity of more than 99%. These results suggest C. blakesleeana AS 3.910 is a useful biosynthetic tool in the preparation of 4′-hydroxytolbutamide.
KeywordsNuclear Magnetic Resonance Biotransformation Tolbutamide CYP2C9 Activity Cunninghamella
This work was supported by Grant 2003AA2Z347C of the 863 Program of China.