An alternative strategy for enhancing stability and antimicrobial activity of catechins by natural deep eutectic solvents

The low stability and loss of antimicrobial activity of catechins limited their application in food preservation. In this study, four kinds of catechins including (−)-epicatechin (EC), (−)-epigallocatechin (EGC), (−)-epicatechin-3-gallate (ECG), and (−)-epigallocatechin-3-gallate (EGCG) were selected as model compounds. Natural deep eutectic solvents (NADES) are a new generation of green solvents that have attracted much attention due to their unique characteristics. The effects of NADES on the stability and antimicrobial activity of catechins were investigated in the present study. Eight typical NADES, especially choline chloride/glycerol (ChG), were found to significantly enhance the thermal and storage stability of catechins. This finding accounted for by hydrogen bonding network formation between ChG and catechins, confirmed by FT-IR and 2D NMR analysis. Additionally, ChG decreased the minimum inhibitory concentration of catechins on Gram-positive and Gram-negative bacteria, which may be associated with its stabilizing property. The stability of catechins combined with NADES revealed their potential of applications in the food industry.