Functionalization of phenolics-rich pigments from purple corn (Zea mays L.) by an enzymatic treatment as a strategy to improve thermal stability and bioactivity

Abstract

The impact of enzymatic treatment of Candida antarctica lipase B on a phenolics-rich extract from purple corn (Zea mayz L.) (PCE) was evaluated. PCE was obtained by solid-liquid extraction with 80% ethanol. PCE was treated with lipase B in acetonitrile using octanoic acid as acyl donor for 72 h. Treated and non-treated PCE were tested for thermal stability at 80°C, α-glucosidase inhibitory activity, and molecular docking. The enzymatic treatment promoted the generation of a reaction product identified by HPLC-UV along with a bathochromic shift (530 nm to 570 nm) in the PCE. Enzymatic treatment increased (p < 0.05) the half-life of total monomeric anthocyanins in solution at 80°C from 6.05 to 10.05 h. Additionally, enhanced (p < 0.05) the α-glucosidase inhibitory activity at a concentration of 0.5 mg eq. C3G/L (11.7% non-treated and 33.2% treated). Molecular docking using predicted acylated structures of major anthocyanins in PCE was correlated with biochemical evaluation on α-glucosidase; for instance, cyanidin-3-(6″-n-octanoyl)-glucoside (-9.4 kcal/mol) had a more favorable binding energy than non-acylated cyanidin-3-O-glucoside (-8.4 kcal/mol) with the catalytic site of α-glucosidase. A ligand-protein interaction analysis showed that the acyl group plays an important role stabilizing anthocyanins in the catalytic cavity of α-glucosidase. The results suggest that treatment with lipase B is a promising strategy to improve technological and biological potential of pigments from purple corn.