Evaluation Methods Of The Antioxidant Activities Of Antioxidants

Lipid oxidation is a common phenomenon. Antioxidants have been widely used to slowthe oxidation induction and inhibit fat oxidation. Different antioxidant activities may exhibitin different substrates or at different reaction conditions even for the same antioxidant.Moreover, the varieties of antioxidants and evaluation methods cause the difficulty toconstruct a unified or an efficient evaluation method to evaluate the antioxidant activities.Based on the mechanism of both lipid oxidation and the antioxidants, the paper established acomprehensive evaluation method to illustrate the effect of the antioxidants in the process oflipid oxidation. In addition, the proposed method may have certain help for the antioxidantsselection and some relative researches.The main research contents and results are as follows:1. The rates of hydroxyl radical scavenging, the rates of superoxide anion clearance andthe rates of inhibition of lipid oxidation (TBARS) were chosen to evaluate the antioxidantactivities of BHQ, BHT, BHA and their complexes with VEor VCor VEand VC. Theexperimental results showed that TBHQ, BHT and BHA had good hydroxyl radicalscavengings, but poor superoxide anion clearances. When separately added TBHQ, BHT andBHA to VE, the rates of hydroxyl radical scavenging were fluctuate compared with the singleantioxidants. When separately added TBHQ, BHT and BHA to VC, the rates of inhibition oflipid oxidation improved compared with the single antioxidants. When separately addedTBHQ, BHT and BHA to VEand VC, the rates of hydroxyl radicals scavenging were improved,the rates of inhibition of lipid oxidation were almost the same and the rates of superoxideanion clearance were negative compared with the single antioxidants.2. The above mentioned methods were also used to to evaluate the antioxidant activitiesof procyanidins, seaweed polysaccharides, polyphenols and their complexes with VEor VCVEor VCor VEand VC. The experimental results indicated that the three types of singleantioxidants had well the rates of inhibition of lipid oxidation. When separately added thesingle antioxidants to VE,the rates of inhibition of lipid oxidation increased about15%, butthe rates of superoxide anion clearance were not improved. When separately added the singleantioxidants to VEand VC, the rates of hydroxyl radical scavenging were almost the same andthe rates of superoxide anion clearance were reduced significantly.3. The composite score S (S=S1+S2+S3, where, S1, the rates of hydroxyl radicalscavenging; S2, the rates of superoxide anion clearance; and S3, the rates of inhibition of lipidoxidation) and regression analysis with Minitab software were used to analyse4kinds ofantioxidants (JN1, JN2, JN3had4components and JN4had6components). The experimentalresults showed that the regression equations were low efficiency except for JN4. JN4can betrusted in the significant level α=0.05. The test result was good consistent with the analysisresult when the formulation of JN4was optimizated.4. Based on the POV values determination and the dynamic analysis of safflower oil with or without antioxidants, it was found that the safflower oil oxidation was obeyed thefirst-order kinetics process at30°C,50°C,60°C,70°C and80°C and all the correlationcoefficients were greater than0.9900. In addition, the changing trends of the reaction rateconstants and active energies of safflower oil oxidation with or without antioxidants atdifferent temperatures were the same. Combining the experimemts results got above, it wasrevealed that the higher rate of scavenging free radicals, the stronger antioxidant activity theantioxidant had.5. The proposed evaluation method, which based on the rates of hydroxyl radicalscavenging, the rates of superoxide anion clearance, the rates of inhibition of lipid oxidation(TBARS) and together with regression analysis and the kinetic analysis, could be useful toevaluate the antioxidant activities of antioxidants.