Additive Capacity of [6]-Shogaol and Epicatechin to Trap Methylglyoxal

Methylglyoxal (MGO), a reactive dicarbonyl species, is thought to contribute to the development of long-term pathological diabetes as a direct toxin or as an active precursor of advanced glycation end products (AGEs). Trapping MGO by dietary phenols to inhibit the MGO induced AGE formation is an approach for alleviating diabetic complications. The present study investigated whether dietary compounds with different structures and active sites have the additive capacity to trap MGO. Ginger phenolic constituent [6]-shogaol and tea flavonoid (-)-epicatechin were selected and tested under simulated physiological conditions, showing that they additively trapped about 41% MGO at a concentration of 10 μM within 24 h. Furthermore, whether [6]-shogaol and epicatechin can retain their MGO trapping efficacy in vivo or a biotransformation limits their MGO trapping capacity remain virtually unknown. An acute mouse study was carried out by giving a single dose of [6]-shogaol, epicatechin, and the combination of both ([6]-shogaol + epicatechin) through oral gavage. A mono-MGO adduct of [6]-shogaol was identified from [6]-shogaol and [6]-shogaol + epicatechin treated mice, and mono- and di-MGO adducts of epicatechin and its metabolite, 3′-O-methyl epicatichin, were detected in urine samples collected from epicatechin and [6]-shogaol + epicatechin treated mice. To our knowledge, this is the first study demonstrating the additive MGO trapping efficacy of [6]-shogaol and epicatechin and that [6]-shogaol and epicatechin retained their MGO trapping capacity in mice.