Isolation, Purification And Structure, Anti-oxidation Of Polyphenol From Longan Seed

The extraction, purification, composition and anti-oxidation activity of polyphenols from longan seed obtained (Fujian province) were researched in this paper. And the conditions of its microencapsulation by spray drying method were discussed as well. The experimental results were as follows:(1)The polyphenols of longan seed were extracted by alcohol and ultrasound-assisted method. On the the basis of single factor experiments, the surface response experiments were performed to determine optimum technical conditions. The optimum extraction conditions using ethanol method were: extraction time of 106 minutes, ethanol concentration of 58 %, extraction temperature of 64℃, ratio of extraction solvent to solid of 9:1, the longan seed polyphenols extracted were 42.690 mg/g under these conditions. The optimum extraction conditions of ultrasound-assisted method were: extraction temperature of 69℃, extraction time of 106 minutes, ultrasonic power of 162 W, and the yield of longan seed polyphenols were 42.209 mg/g on these condition. The extraction efficiency of ultrasonic method was slightly lower than the ethanol method, while the extraction time was obviously shorter than the latter.(2)The longan seed polyphenols were purified by DM21 macroporous adsorption resin. The results assorption kinetics and thermodynamics experiments showed that, the adsorption of longan seed polyphenols on DM21 macroporous resin was an endothermic and membrane diffusion process. The static and dynamic experments showed that the optimum conditions for column chromatography were: pH of 4.2, polyohenols concentration of 1 mg/mL, and the flow rate of 5 BV/h; the eluant concentration of 70 % ethanol and the elution flow rate of 1.5 BV/h. The yields and purity of longan seed polyphenols made under these conditions was 5.2 % and 74.14 % respectively.(3)The color reaction indicated that the characteristic response of flavonoids and phenolic hydroxyl groups from the longan seed polyphenols was obvious. The results of UV-visible spectroscopy showed that the longan seed polyphenols contained flavonoids.The results of infrared spectroscopy showed that the longan seed polyphenols probably contained acidic polyphenols which was acetylated. And the HPLC chromatography using acetonitrile-0.1 % formic acid as the mobile phase showed that the longan seed polyphenols contained epicatechin and rutin, and the content of epicatechin was up to 21.35 %.(4)The anti-oxidation experiments of the longan seed polyphenols showed that the trend of clearing DPPH., .OH and O2-. free radical was similar, the clearing rate increased with polyphenols concentration, when the concentration of polyphenols reached a certain concentration, the clearing rate was almost constant. The IC50 of longan seed polyphenols in clearing DPPH. , .OH and O2-. free radical was 0.4326 mg/mL, 142.4 mg/mL and 99 mg/mL respectively; The IC50 of Vc was 0.7292 mg/mL, 63.94 mg/mL, 15.91 mg/mL respectively, the effect of longan seed polyphenols on scavenging DPPH. free radical was surpass than Vc.(5)The longan seed polyphenols were embedded by spray drying method, usingβ-cyclodextrin and gum arabic as wall material. The results showed that the wall material ratio (gum arabic:β-cyclodextrin) was 1.5:1, the ratio of core to wall was 1:6, monoglyceride content was 0.1 %. The orthogonal experiments showed that the optimum conditions of microencapsulation longan seed polyphenols by spray drying were: solids content was 14 %, the inlet temperature was 200℃, the feed rate was 3.5 mL/min. The micro-encapsulation rate of longan seed polyphenols under the optimum conditions was 91.39 %. The microcapsulation of longan seed was light yellow, no smell, the density was 0.667 g/cm3, its water content was 3.92 % and solubility was 95.86 %.