Effects of biotransformation of prenylated flavonoids on antioxidative capacity

Flavonoids are polyphenolic compounds presented as constituents of plants, particularly of food plants. More than 4,000 flavonoids have been found in fruits, vegetables, and beverages. And some of them were identified as significant natural antioxidants [1]. In the bioactivity studies, structural features such as number and position of hydroxyl groups or other modifications like methylation, prenylation, glycosylation, etc., are key factors influencing the selectivity and strength of potential activities. Therefore, the impact on the biological activities of flavonoids can hardly be predicted with even minor modifications [2, 3]. In the present study, the biotransformation of a series of prenylated flavonoids was investigated with twenty different microbial strains to discover new metabolites. It was revealed that Mucor hiemalis was the most appropriate microorganism which was capable of transforming these flavonoids. Structures of the new metabolites were elucidated as 4'-O-prenylquercetin 3-O-β-D-glucopyranoside and 7-O-prenylquercetin 3-O-β-D-glucopyranoside by spectroscopic methods. The microbial metabolites and their respective parent compounds were further evaluated for their antioxidant capacity by DPPH assay. It was concluded, however, that decreased activity of the metabolites suggested that the free hydroxyl group at C-3 position was a crucial factor for the antioxidant activity. In addition, the existence of a flavonoid glucosidase was indicated for M. hiemalis which may provide a potent approach to prepare glucosylated products of free flavonoids.

Acknowledgements: Chonnam National University Center for Research Facilities is acknowledged for running NMR experiments.

Keywords: Biotransformation, prenlyated flavonoids, antioxidative activity.

References:

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