Investigations on the Reaction of C3 and C6 α-Dicarbonyl Compounds with Hydroxytyrosol and Related Compounds under Competitive Conditions.

α-Dicarbonyl compounds are intermediates in reactions that lead to the formation of potentially harmful advanced glycation end-products. Carbonyl-trapping capacities of antiglycative substances have been traditionally limited to C2 and C3 α-dicarbonyl structures. Glyoxal (GO)-, methylglyoxal (MGO)-, 3-deoxyglucosone (3-DG)-, 3-deoxygalactosone (3-DGal)-, 3,4-dideoxyglucoson-3-ene-, and glucosone-trapping capacities of hydroxytyrosol (HT), hydroxytyrosol acetate (HTA), and 3,4-dihydroxyphenylacetic acid (DOPAC) in simple (phenolic/dicarbonyl) and competitive model systems (phenolic/dicarbonyl1/dicarbonyl2) were investigated. HT and HTA were more effective for MGO than 3-DG and 3-DGal. Furthermore, DOPAC exerted higher trapping capacity than HT and HTA for C3 and C6 α-dicarbonyl compounds. In the competitive systems, HT-related substances did not show preference for trapping 3-DG or 3-DGal and behaved as in the simple systems. In the presence of MGO, however, HT-related substances were more effective for trapping MGO than C6 structures. The results demonstrate the C6 α-dicarbonyl-trapping capacities of HT, HTA, and DOPAC, with DOPAC exerting the highest activity.