ANTIOXIDANT EFFECTS OF DOPAMINE AND RELATED-COMPOUNDS

The antioxidant and free radical scavenging effects of dopamine, norad renaline, tyramine, and tyrosine were investigated and compared with a lpha-tocopherol. The antioxidant effect of dopamine and its related co mpounds on peroxidation of linoleic acid were in the order of dopamine > alpha-tocopherol = tyramine > tyrosine > noradrenaline as measured by the thiocyanate method. These amine compounds had reducing power, a nd a scavenging effect on reactive oxygen species, i.e., superoxide an ion and hydroxyl radical. The results for reducing power and scavengin g effect of these amine compounds had a similar trend as their inhibit ion of linoleic acid peroxidation. The antioxidant activity of these a mine compounds in soybean oil was also evaluated by the Rancimat metho d. The induction time to reach 100 meq/kg peroxide value (POV) of soyb ean oil for dopamine, alpha-tocopherol, tyramine, tyrosine, noradrenal ine, and control were 9.0, 8.2, 8.0, 6.4, 4.6, and 4.3 h, respectively . The antioxidant efficacy of amine compounds seems to be correlate wi th the numbers of hydroxy groups and their position on the phenolic ri ng.