Study On The Extraction And Purification And Antioxidant Of Anthocyanin Of Purple Sweet Potato

Purple sweet potato (Ipomoea batatas L.) is an annual hebaceous plant within Ipomoea of Convolvulaceae. It has good characteristics of adaptability and economy, high and stable yields and low cost; Anthocyanins in purple sweet potato has a great development value because it has a lot of physiological effects such antioxidant, antimutagenic, antibacterial, hypotensive and so on. In this dissertation, the extraction technology of purple sweet potato anthocyanins was studied, and then a study on the purification process of two grade resin was conducted, finally, the composition of anthocyanins from purple sweet potato by different purification products were analyzed at a preliminary stage, and the antioxidant properties of the purified product was studied at last. The main results were summarized as follows:(1) With acidic enthanol as reagent, the optimum process parameters for the extraction of anthocyanin from purple sweet potato by response surface method associated with factorial design were obtained:Solvent 60% ethanol (pH value is 2.0),ratio of liquid to solid 40:1, extraction time 84min and extraction temperature74℃; The optimized extraction ratio was obtained after 74℃ and 84 min, leading to the extraction ratio of 419.529mg/100g. Purple sweet potato power was extracted for three times, the extraction ratios were 91.86%、 6.40% and 1.74%.Accordingly, the extraction time was selected for 1.(2) Two grade resins purification process was divided into three steps:First, the conditions of static adsorption and desorption of AB-8 resin and polyamide resin was studied. During the inspection of adsorption isotherms of the two resins, multi-molecular layer adsorption was found. They all had better capabilities of absorption and desorption to purify crude purple sweet potato anthocyanins.The conditions of static absorption and desorption of sweet purple anthocyanins were that temperature of absorption was 30℃, the elution solvent was 60% ethanol. Then the purification processes of AB-8 was studied.The simple M2(color value is 32.36, purity is 45.30%) was obtained with the concentration of sample 4mg/mL, sample flow rates 2mL/min, sample volume 20BV and 4BV of desorption eluent 60% ethanol (pH3.0). The purification process of polymide resin was investigated at the same time. The simple M3(color value is 41.67, purity is 58.48%) was obtained with the concentration of sample 4mg/mL, sample flow rates 1.5mL/min, sample volume 14.4BV and 4BV of desorption eluent 60% ethanol (pH3.0). Finally, polyamide column was used for further separation of M2.Four kinds of fractions F1, F2, F3, F4 were obtained with different ethanol gradient elution. The color value and purity were significantly improved. The best recovery effect was obtained by F2(color value is 95.88, purity is 84.24%).(3)The components of different anthocyanins purification products were analyzed. The HPLC profiles of M2 and M3 were found analogous but different with the crude extract of M1. The two purification gradient elution of F1, F2, F3, F4 contained different components, and has less peak amount, which suggests gradient elution can further separation of anthocyanins.(4) The antioxidant activity of anthocyanins from purple sweet potato were studied. All purified products showed a good inhibitory effect on DPPH free radicals and OH free radicals.The antioxidant effect of two purified products were better than M1,M2 and M3, and among the two purified products, F2, F3 showed the bestantioxidant activity. The IC50 on DPPH free radicals and OH free radicals of F2 were 0.002mg/mL and 0.057mg/mL. The IC50 on DPPH free radicals and OH free radicals of F3 were 0.003mg/mL and 0.011mg/mL. All better than the IC50 value of Vc which were 0.003mg/mL and 0.066mg/mL.