Microbial Transformation of Vanillin Isolated from Melia azedarach to Vanillyl Alcohol followed by Protease Inhibition and Antioxidant Activity

Abstract

Vanillin (1) was isolated from ethanolic extract of Melia azedarach L. and incubated in the culture of Aspergillus niger GC-4, which resulted in vanillyl alcohol (2). The product was identified by mass, ¹H and ¹³C-NMR spectroscopy. Protease inhibition potential was measured using in vitro model, which indicated significant enzyme inhibition activity of vanillyl alcohol (2) as compared to vanillin (1). Compound 1 and 2 were screened for antioxidant activity using phosphomolybdate and diphenyl picrylhydrazyl (DPPH) in vitro model systems. Dose-dependant increase in the antioxidant activity of vanillyl alcohol was observed in phosphomolybdate method, while vanillin was found to be inactive. Vanillyl alcohol showed remarkable decay of the free radicals in the solution of DPPH within first two minutes which finally became constant after five minutes. In contrast, vanillin exhibited much lower antioxidant activity.