Antioxidant and anti-α-glucosidase activities of biotransformable dragon's blood via predicted data mining approach

Bacillus megaterium tyrosinase (BmTYR) has been proven an applicable biocatalyst in the ortho-hydroxylation of flavonoids, which usually possess higher antioxidant activity than their precursors. With a predicted data mining approach (PDMA), putative novel bioactive flavonoids from known precursors may be good candidates for biotransformation by BmTYR. Two flavonoid precursors (loureirin A and loureirin B) were confirmed via this approach, which are the commercial constituents of the Chinese medicine dragon's blood. These two flavonoids were then biotransformed by BmTYR for validation. The results found two novel flavonoids (3 ' -hydroxyloureirin A and 3 '-hydroxyloureirin B), which gained 2.5 and 1.6 times of the antioxidant activity of ascorbic acid, respectively. In addition, all four flavonoids-loureirin A, loureirin B, and the two 3 '-hydroxyl derivatives-possessed 4-22 times the anti-alpha-glucosidase activity of acarbose, a clinical anti-diabetes drug. A further kinetic analysis revealed that the inhibition mode of the four alpha-glucosidase inhibitors was non-competitive, and their kinetic constants (Ki values) were 64.3 +/- 2.5 mu M, 308.7 +/- 10.4 mu M, 69.4 +/- 2.8 mu M, and 325.3 +/- 12.6 mu M, respectively. The high antioxidant and anti-a-glucosidase activity suggest that the two novel flavonoids have potential future applications in pharmacology and biotechnology.