Modification And Application Of Natural Antioxidants

The preparation of Flavonoid-N-Meglumine salts, the structures, the solubility, the scavenging effects on free radicals and inhibiton on tyrosinase were primarily studied in this thesis .The meglumine salts of seven selected flavonoids(silybin, liquiritigenin, isoliquiritigenin, quercetin, rutin, daidzein and puerarin) has been preparated by solvent-heating recirculation method. Their structures were studied by UV, DSC. It was shown that flavonoid-N-Meglumine exists in form of salts, which is different from simple mixture.Because of acidic hydroxybenze- ne of flavonoids molecule combine with basic amido of meglumine. Flavonoid-N-Meglumine can be easily decomposed into flavonoid and meglumine in solutions, and the properties of flavonoid were not changed. Therefore, the DSC curve can be used a reference basis to evaluate the quality of Flavonoid-N-Meglumine.The equilibrium solubility of Flavonoid-N-Meglumine in water at 25℃were measured by standard curve method. It shows that the solubility of Flavonoids in water can be improved significantly via Flavonoids-N-Meglumine and their water-solubility are very good.The scavenging effects on hydroxyl free radical (·OH) and superoxide anion free radical(O2ˉ·) of Flavonoid-N-Meglumine were determined by using three photometric methods.The results showed that Flavonoid-N-Meglumine basically do not change good capacity on scavenging·OH free radical and O₂ˉ·free radical which Flavonoid oneself owns and they can chelated some metal ions. Studying the scavenging effects on superoxide anion free radical(O₂ˉ·) of flavonoid by model of Pyorgallol autoxidation method is not very suitable because of flavonoids be likey to have self-oxidation in alkali condition,The inhibiton of Flavonoid-N-Meglumine on tyrosinase was studied, using L-Tyrosine as substrate,water as solvent, avoiding the effect of Propylene glycol.The results showed that Flavonoid-N-Meglumine have a good inhibiton on tyrosinase.In the same concentration, the upmost inhibiton of meglumine salts of rutin, puerarin, liquiritigenin and isoliquiritigenin are lower than Arbutin, but meglumine salts of quercetin, daidzein and silybin are higher than Arbutin.Especially,silybin-N-Meglumine has the highest inhibiton, shows it can be used in cosmetics abroadly as a perfect natural safe skin-lightening additive.