Trapping of glyoxal by propyl, octyl and dodecyl gallates and their monoglyoxal adducts

Glyoxal (GO) is one of the major toxic intermediates generated during lipid oxidation and degradation. We investigated the inhibitory activities and mechanisms of propyl, octyl, and dodecyl gallates (PG, OG, and DG) on the formation of GO in buffer and during thermo-processing of corn oil, and the anti-carbonyl and antioxidative activities of the mono-GO adducts of PG, OG, and DG. Our results suggested that alkyl gallates could more effectively trap GO than gallic acid. The major mono-GO adducts of PG, OG, and DG were purified and their structures were elucidated based on their H-1, C-13, 2D-NMR, and HRMS data. We further demonstrated that the mono-GO (MG) adducts retained the anti-carbonyl and antioxidative activities. This is the first study to demonstrate that alkyl gallates, the popular food additives, could prevent not only food oxidation, but also the formation of toxic reactive carbonyl species and their corresponding advanced glycation end products (AGEs) during food processing.