α-Glucosidase inhibiton and antiglycation activity of laccase-catalyzed catechin polymers

Catechin polymers were produced by laccase (12 U/mL) in a mixture of sodium acetate buffer (1% (+)-catechin, 100 mM, pH 5) and methanol (buffer:methanol = 95:5, v/v). The freeze-dried catechin polymers were recovered from the precipitate after dialysis followed by centrifugation. Catechin polymers extracted with 20% ethanol had potent inhibitory activity against α-glucosidase with an IC50 value of 4 μg/mL, and they were present as a mixture of dimers, trimers, and tetramers. The antihyperglycemic effect of the catechin polymers was confirmed by an oral maltose tolerance test. The catechin polymers also had significantly improved antiglycation and superoxide dismutase-like activities compared to those of (+)-catechin. Since formation of advanced glycation end products and oxidative stress are accelerated in hyperglycemic conditions, we suggest that enzymatic production of catechin polymers could have a potential protective effect in type 2 diabetes, diabetic complications, and other free radical related diseases.