Influence of Quercetin and Its Methylglyoxal Adducts on the Formation of α-Dicarbonyl Compounds in a Lysine/Glucose Model System

Abstract

Increasing evidence has identified α-dicarbonyl compounds, the reactive intermediates generated during Maillard reaction, as the potential factors to cause protein glycation and the development of chronic diseases. Therefore, there is an urgent need to decrease the levels of reactive dicarbonyl compounds in foods. In this study, we investigated the inhibitory effect of quercetin, a major dietary flavonoid, and its major mono- and di-MGO adducts on the formation of dicarbonyl compounds, such as methylglyoxal (MGO) and glyoxal (GO), in a lysine/glucose aqueous system, a model system to reflect the Maillard reaction in food process. Our result indicated that quercetin could efficiently inhibit the formation of MGO and GO in a time-dependent manner. Further mechanistic study was conducted by monitoring the formation of quercetin oxidation and conjugation products using LC-MS/MS. Quercetin MGO adducts, quercetin quinones, and the quinones of quercetin MGO adducts were detected in the system, indicating quercetin plays a dual role in inhibiting the formation of MGO and GO by scavenging free radicals generated in the system and trapping of MGO and GO to form MGO adducts. In addition, we prepared the mono- and di-MGO quercetin adducts and investigated their antioxidant activity and trapping capacity of MGO and GO. Our results indicated that both mono- and di-MGO quercetin adducts could scavenge the DPPH radical in a dose-dependent manner with >40% DPPH scavenged by the MGO adducts at 10 μM, and the di-MGO quercetin adduct could further trap MGO to generate tri-MGO adducts. Therefore, we demonstrate for the first time that quercetin MGO adducts retain the antioxidant activity and trapping capacity of reactive dicarbonyl species.

Antiglycating Effect of Phenolics from the Chilean Currant Ribes cucullatum under Thermal Treatment

“…A decrease in the amount of CML and glyoxal by dietary polyphenols has been observed in the thermal processing of cookies [ 28 ]. In addition, scavenging reactions between methylglyoxal and quercetin have been reported to occur in the A-ring of the flavonoid [ 29 ]. We have observed that PEE from R. cucullatum exert a significant reduction of lipid-derived electrophiles levels (expressed as MDA IC 50 ) generated by lipid peroxidation reactions in an in-vitro gastric digestion model.…”

Impact and inhibitory mechanism of phenolic compounds on the formation of toxic Maillard reaction products in food

“…Several proanthocyanidins from cinnamon bark have been identified as inhibitors of specific AGE representatives, which were largely attributed to both their carbonyl scavenging abilities as well as antioxidant activities [59] . Another report also indicated that quercetin has a dual role inhibiting MGO formation by scavenging free radicals produced in the system, while concurrently trapping MGO to form adducts [51] .…”

“…4). In Liu's research [51] , quercetin could effectively inhibit the formation of both GO and MGO in a time-dependent manner in a glucose/ lysine Maillard reaction model system, and the di-MGO Fig. 4 The possible pathways for AGE formation as well as inhibitory strategy and structures of some typical reactive carbonyl compounds and AGEs quercetin adduct could further trap MGO to produce tri-MGO adducts.…”

“…On the other hand, Amadori products can dehydrate and rearrange to form reactive dicarbonyl compounds ( Fig. 4) [49] , such as methylglyoxal (MGO) and glyoxal (GO), which are typical α-dicarbonyl compounds, and can actually also serve as significant precursors for the formation of AGEs, through their subsequent reactions with protein amino, sulfhydryl and guanidine functional groups [50][51][52] . According to their fluorescence and crosslinking properties, AGEs can be divided into four categories, which are fluorescent crosslinking compounds, non-fluorescent crosslinking compounds, fluorescent noncrosslinking compounds and non-fluorescent non-crosslinking compounds.…”

“…A range of polyphenols have been reported for their inhibitory effects against AGE formation in both chemical models and food models [19,42,51,53,57,58] . In studies conducted using chemical models, Sang et al [57] found that below 37°C at pH 7.4, EGCG can trap GO and MGO, two intermediates for AGE formation, to form mono-and di-GO or MGO adducts, and the data from LC/MS and NMR indicated that C6 and C8 on the A-ring of EGCG were the key positions for trapping ( Fig.…”