Four Common Antioxidants In Food:Their Interactions And The Mechanisms Of Synergy

Food diversity is one of the important principles of a rational diet. However, there were few researches on the interaction and the mechanisms of synergy between different antioxidants in food. Chlorogenic acid, quercetin, catechin and ferulic acid are widely distributed in plant food. People pay attention to them because of their of antioxidant, anti-tumor, lowering blood pressure, lowering blood lipids, cardiovascular protection effect and inhibition of bacteria and other biological characteristics. They are widely applied in medicine, health products, cosmetics raw materials and food additives. In vitro the synergistic antioxidant activity and the dose-effect relationship of these compounds were analyzed by DPPH free radical scavenging assay, ABTS free radical scavenging assay and Ferric Reducing Antioxidant Power (FRAP) assay; their synergistically protective effects on cells and regulatory effects on antioxidant enzymes in cells were researched in a HepG-2 oxidative damage model. And the results of the chemical and cellular methods were compared. All of these would provide a scientific basis for dietary diversity theory and help them be used as functional foods and dietary supplements. The major findings of my study were as below:1. It was found that quercetin and catechin, which are flavonoids, were of better antioxidant capacity than chlorogenic acid and ferulic acid, which are phenolic acids.2. By analyzing the results of the 3 in vitro assays, there was relatively small probability of synergistic antioxidant effect between flavonoids was found. Flavonoids with non-flavonoids or non-flavonoids with non-flavonoids produced more synergistic effects, especially chlorogenic acid with the other 3 compounds.3. Chlorogenic acid, catechin, quercetin and ferulic acid have shown protective effects on the H2O2-induced damage of HepG-2 human hepatoma cells, and the effects were of a dose-effect relationship. All of these compounds have shown a synergistically antioxidant activity when used together with another one of them.4. Treating the cells with chlorogenic acid, catechin, quercetin and ferulic acid could significantly improve the activities of intracellular SOD, GSH-Px and CAT, and inhibit the production of MDA; the combination of chlorogenic acid (5?M) and ferulic acid (1.25?M) and the combination of chlorogenic acid (20 ?M) and quercetin (100 ?M) showed synergistic effect on improving the activities of T-SOD, Cu/Zn-SOD and CAT, which might be one of the mechanisms of synergy for the combinations.5. The crude extracts of purple wheat bran showed synergistic effects with chlorogenic acid and additive or antagonistic effects with the other 3 compounds in DPPH and ABTS assay. This finding would provide a theory basis for product development of purple wheat bran.