Study On The Extraction, Isolation And Antioxidant Activity In Ziziphus Jujube Mill. Var. Spinosa

Ziziphus jujube Mill. var. spinosa is a common Chinese medicinal plant, the effective compounds of Ziziphus jujube which have high antioxidant activity can be developed into natural antioxidants or health products. This dissertation studied the antioxidant activity of effective compounds of Ziziphus jujube systematically. The compounds whose antioxidant activities are highest have been found by bioassay-guided method and identified. We also study the synergy of the isolated compounds.The antioxidant activity of Ziziphus jujube oils isolated by different methods has been studied. The oils contain plenty of unsaturated fatty acid, and the antioxidant activities of oils isolated by supercritical CO2 extraction and microwave assisted extraction are as well as that of synthetic antioxidant BHT, but much higher than that of the oil isolated by Soxhlet extraction.The condition for extracting of antioxidant compounds of Ziziphus jujube has been established. After study by single factor experiment, orthogonal experimental and response surface design, the optimum conditions are determined as follows:adding the powder of Ziziphus jujube defatted by petroleum ether into 10 times ethanol by volume radio of 59.1%, circulation refluxing one time at the temperature of 76.5℃for 4.5 hours, collecting the extract and concentrating by reduced pressure to obtain the crude product whose antioxidant activity is highest.Ethyl acetate phase has been determined to be the part whose antioxidant activity is highest, and the condition for isolating of antioxidant compounds by polyamide resins has been established. The best condition is:feeding concen-tration is 5mg/mL, the flow rate of elution is 5mL/min. A gradient is formed by varying the proportion of water (A) and MeOH (B). The elution system was:0-27 min, isocratic 30% B; 27-37 min, linear gradient 30-80% B; 37-75 min, isocratic 80% B, and the fraction B has the highest antioxidant activity.The condition for isolating of antioxidant compounds by low-pressure preparation C18 column chromatography has been optimized. The best condition is:linear elution solution is MeOH/H2O=4:6, v/v for 60 minutes, the flow rate of elution is 5mL/min, and the fraction B2 has highest antioxidant activity.The molecular weights and structures of the active fraction A, B1, and B2 are analyzed by the mass spectrometry (MS) and nuclear magnetic resonance (NMR), and the result is that A is zizyphusine, B1 is spi- nosin, and B2 is 6"'-feruloylspinosin.The antioxidant activities of different products from operating units of extraction, separation, and purification processes, and different compounds of Ziziphus jujube have been tested.6"'-feruloylspinosin is proved to have highest antioxidant activity.The interaction among zizyphusine, spinosin, and 6"'-feruloylspinosin has been studied. The results have shown the interactions among zizyphusine, spinosin and 6"'-feruloylspinosin were synergistic and additive effects by using metal ion chelating method, and antagonistic effects by both T-AOC and DPPH methods.