Flavone Biotransformation by Aspergillus niger and the Characterization of Two Newly Formed Metabolites

摘要

Aspergillus niger isolated from Allium sativum was used at large scale fermentation (150 mg flavone/200 ml medium) to obtain suitable amounts of the products, efficient for identification. Then spectral analysis (UV, IR, 1H-NMR, 13C-NMR) and mass spectrometry were performed for the two products, which contributed to the identification process. The metabolite (1) was identified as 2'-hydroxydihydrochalcone, and the metabolite (2) was identified as 2'-hydroxyphenylmethylketone, which were more active than flavone itself. Antioxidant activities of the two isolated metabolites were tested compared with ascorbic acid. Antioxidant activity of metabolite (1) was recorded 64.58% which represented 79% of the antioxidant activity of ascorbic acid, and metabolite (2) was recorded 54.16% (67% of ascorbic acid activity). However, the antioxidant activity of flavone was recorded 37.50% which represented 46% of ascorbic acid activity. The transformed products of flavone have antimicrobial activity against Pseudomonas aeruginosa , Aspergillus flavus and Candida albicans , with MIC was recorded 250 μg/ ml for metabolite (2) against all three organism and 500, 300, and 300 μg/ ml for metabolite (1) against tested microorganisms ( P. aeruginosa , Escherichia coli , Bacillus subtilis , and Klebsiella pneumonia , Fusarium moniliforme , A. flavus , Saccharomyces cerviceae , Kluveromyces lactis and C. albicans ) at this order.