Studies On The Antioxidant Activities Of Proanthocyanidins From Chinese Bavberry (Myrica Rubra Sieb. Et Zucc.) Leaves In Oil

Proanthocyanidins (PAs) are natural phenolics with a basic structure of C6-C3-C6. They are known for a wide range of biological and pharmacological activities, which include antioxidative, antitumor, cardioprotective effects. Bayberry (Myrica rubra Sieb. et Zucc.) leaves are rich in PAs. Proanthocyanidins from Chinese bayberry leaves (PCBLs) are of the prodelphinidin type consisting mostly of epigallocatechin-3-O-gallate. Extracts of bayberry leaves have been reported to be antioxidative, antimicrobial, and antiviral. However, recent research on PCBLs is limited. The utilization of leaves, which are generally discarded and remain underutilized, has the practical application value.In this study, antioxidant activities of PCBLs during different extractive methods in lard oil were evaluated to screen out the best PCBLs for later research. The antioxidant activities of the best PCBLs in lard oil and soybean were also investigated. Meanwhile, the synergistic antioxidant effects of PCBLs and BHT or TBHQ were explored. Finally, antioxidant activities of PCBLs in ham were studied. The main results of this paper were summarized as follows:1. PCBLs during different extractive methods could inhibit the oxidation of lard oil. However, the ability varied during the different extractive methods. Refined extract of macroporous resin (RE) was more potent than the other three extracts in preventing lard oil oxidation due to its higher contents of PAs. In the Schaal assay, RE could more effectively inhibit the increasing of peroxide value, acid value, thiobarbituric acid reactive substances value,p-anisidine value, total oxidation value. Moreover, the lard oil containing RE had lower total volatile compounds, and higher unsaturated fatty acid content. In the Rancimat assay, RE could be more useful in lengthening the induction period of lard oil and the induction period of RE was between BHT and TBHQ.2. PCBLs could inhibit the oxidation of lard oil and soybean oil. PCBLs led to a lowering of the peroxide value, acid value, thiobarbituric acid reactive substances value, p-anisidine value, total oxidation value and had lower total volatile compounds, higher induction period, and higher unsaturated fatty acid content. The antioxidant activity of PCBLs in oil enhanced with the increasing of additive amount, indicating that there was dose-effect relationship between additive amount and antioxidant activities.3. There was a synergistic antioxidant effect between PCBLs and BHT or TBHQ. The antioxidant activities of PCBLs in the presence of BHT or TBHQ were studied using inhibitory assay on peroxidation of yolk lipoprotein combined with isobologram method. PCBLs had good inhibitory effect on peroxidation of yolk lipoprotein. The effect points of PCBLs combined with BHT or TBHQ were observed below the addition line with 95% confidence interval in isobolographic plots. Meanwhile, there was significant difference between theoretical IC50add value and experimental ICsomix value by statistical analysis. All the interaction indexes of each combination were less than 1. These results indicated that there was a synergistic antioxidant effect between PCBLs and BHT or TBHQ, showing promising prospects in practical applications. PCBLs could improve the antioxidant activities of synthetic antioxidants and reduced the usage amounts of synthetic antioxidants, which could avoid the side effects of high-dose synthetic antioxidants.4. PCBLs could inhibit the oxidation of ham. PCBLs could inhibit the increasing of the peroxide value, thiobarbituric acid reactive substances value, total volatile basic nitrogen. Meanwhile, PCBLs could delay the formation of volatile compounds and inhibit the increasing of nonanal. There were siginificant differences between the samples adding 0.05% PCBLs,0.125% PCBLs and the control samples. PCBLs could increase the proportion of unsaturated fatty acid. The proportions of unsaturated fatty acid were no siginificant differences between the samples adding 0.02% PCBLs, 0.05%PCBLs and BHT. Meanwhile there were no siginificant differences between the samples adding 0.125% PCBLs and TBHQ.