Studies On The Antioxidant Activity Of Apple Ciders And Its HPLC Fingerprint Chromatograph

In this dissertation, six kinds of apple ciders were studied by chemical methods and quantum-chemical method. Firstly, The process for extracting phenolic compounds from apple ciders was designed by choosing resins and optimizing the condition of absorption and desorption, then the bioactivity of phenolic acids was studied. Secondly, the apple ciders were analysed by Reversed-Phase High Performance Liquid Chromatography with Electronic Chemistry Detection according to the nine standard phenolic acid samples. Finally, structure-activity of three kinds of phenolic compounds contained in apple ciders were evaluated by the quantum chemistry method. The results provided the theoretical background for the design of new antioxidant.LSA-800B resin was excellent for extraction of phenolic compunds from apple ciders, the adsorbing capacity is 113.81μg.mL^-1, 85% ethanol solution was better for desorption. The phenolic acids showed strong inhibitory ability to colibacillus and staphylococcus. Antioxidant properties of apple ciders and extract were evaluated using four different methods. The results from this study indicated that a positive correlation between total phenolic content and antioxidant activity in DPPH radical, superoxide anion radical and reducing power system, but not exist in lipid peroxidation system.We used RP-HPLC with Electrochemical method to determine phenolic acids. The results pointed to great variety differences in phenolics and contents in six apple ciders. Caffeic acid, chlorogenic acid and protocatechuic acid were detected in all apple ciders. The quality differences in various batches and various manufactures of apple dders were investigated by using the similarity coeffident among chromatographic fingerprints. The fingerprints were positioned with index composition such as chlorogenic add. Eight common peaks were analysed. Then, we set up the HPLC fingerprint chromatogram similarity of 14 samples and found the correlation among them.Three kinds of phenolic antioxidants, such as protocatechuic add, caffeic add, chlorogenic add, were calculated by DFT/B3LYP methods in GaussianO3 package at the 6-311G basis set level. The structural characters and activity relationships were analyzed according to the calculation results. It has been founded atomic net charge, constitutes and energy of frontier molecular orbital, gas-phase bond dissocaiation enthalpies (BED), the difference between the heat of formation of antioxidant and its free radical (AHOF) for molecules correlated well with the free radical scavenging rate constant for phenolic adds. On the basis of these parameters, we interpreted the relative rates for reaction of antioxidants with free radicals, including a comparison of both ortho position and contra-position of phenolic hydroxyl groups, and concluded that in most cases H-atm transfer was dominant. The calculation results indicated the overall evaluation of antioxidative activities in the following order caffeic add >chlorogenic add > protocatechuic add.