# Effects of C-Ring Structural Differences on the Inhibition of Nε-(Carboxyethyl)lysine in the Methylglyoxal-Lysine System by Flavonoids

## TL;DR

This study explores how the C-ring structure of flavonoids affects their ability to inhibit the formation of Nε-(carboxyethyl)lysine in a chemical reaction system.

## Contribution

The study reveals how specific C-ring structural features influence the inhibitory effects of flavonoids on CEL formation.

## Key findings

- Cat showed the highest inhibition rate of 53.78%, while Lute had the lowest at 3.97%.
- Hydroxylation at C3 on the C-ring enhances inhibition, while the C2-C3 double bond and C4 carbonyl group reduce it.
- Flavonoids inhibit CEL by capturing methylglyoxal and reducing lysine consumption.

## Abstract

This study investigated the effects of taxifolin (Tax), quercetin (Que), (+)-catechin (Cat) and luteolin (Lute) on the advanced Maillard reaction stage in the methylglyoxal-lysine (MGO-Lys) system. Since the four flavonoids share identical A- and B-ring structures, the inhibitory effects and molecular mechanisms of flavonoids with different C-ring structures on Nε-(carboxyethyl)lysine (CEL) formation were revealed. The results demonstrated that Cat exhibited the best inhibitory effect on CEL with an inhibition rate of 53.78%, while Lute showed the lowest inhibition rate of 3.97%. The flavonoids (i.e., Tax, Que, Cat and Lute) inhibited the formation of non-fluorescent CEL, where hydroxylation at C3 on the C-ring favored the enhancement of the inhibitory effect of the flavonoids on CEL, while the C2-C3 double bond and the carbonyl group at the C4 position reduced their inhibitory ability. The alkaline environment favored the enhancement of the inhibition of CEL by Tax, Que, Cat and Lute. Notably, Tax, Que, Cat and Lute can inhibit CEL formation by competitively capturing MGO to form mono- or di-adducts and reducing lysine consumption. This study provides innovative strategies and a theoretical foundation for developing effective CEL inhibitors in food thermal processing.