Effect of pH on the reaction between naringenin and methylglyoxal: A kinetic study

•Reaction rate between naringenin and MGO is highly pH dependent.•Reaction between naringenin with methylglyoxal is base-catalyzed.•Deprotonated naringenin is the main reactant.•Reaction rate of methylglyoxal with naringenin is higher than that with arginine and lysine.•Naringenin can trap MGO dissociated from cysteine-MGO adduct. Methylglyoxal (MGO) is a highly reactive ɑ-dicarbonyl compound that may adversely impact food quality and human health by modifying proteins. The kinetics of the reaction of naringenin with MGO was studied at pH 6–8 and 37 °C by UV–Vis spectrophotometry and reaction products were characterized by liquid chromatography-mass spectrometry (LC-MS/MS). The apparent second order rate constant (k2) increased at pH above the lowest pKa value of naringenin, indicating deprotonated naringenin as the main reactant. A Lederer-Manasse type reaction mechanism is suggested, with dehydration of the MGO-dihydrate as a rate determining step. The quantitative data obtained in the present study was used to simulate the competitive reaction between MGO and nucleophilic amino acid residues (Lys, Arg and Cys) and naringenin in milk. It is predicted that naringenin will be able to efficiently trap MGO during storage of milk, although the reversible trapping of MGO by Cys residues is initially kinetically favourable.