| Gongcheng persimmon is mainly produced in Gongcheng County, Guangxi province. It was known as the "fruit of China" because of its bright color, crisp and sweet taste. Gongcheng persimmon will produce 15% to 20% fruit drop and fruit thinning in the planting process annually, which could not be utilized fully because of high tannin content and less sugar. The study showed that tannins had ability of antioxidant, anti-allergy, tumor growth inhibition, immunity enhance and other functions. Currently, the tannins research had some questions like difficult purification, lower than food and drug safety and quality standards. Resources wasting could be avoided by improving extraction method and purification process.Astringent persimmon(Gongcheng persimmon) was as raw materials in this paper to determine the method of the extraction of tannin, the separation process and obtain the optimal process conditions.Otherwise the study of antioxidant activity of Gongcheng persimmon tannin can provide a theoretical basis for the efficient utilization of persimmon tannin.In this study, a method of optimization of persimmon tannin extraction process is using ultrasonic assisted extraction.The optimum conditions obtained by single factor test and response surface is as follows: ethanol concentration was 40%(v/v), extraction temperature was 55?, solid to liquid ratio was 1:15, ultrasonic power was 300 W,time was 1h. Under this condition, the extraction of persimmon tannin hydrolysis was 23.64 mg / g, and the production of condensed tannin extract was 30.42 mg / g. Their extraction rate was 80.61% and 83.58% respectively.The process of isolated and purified. hydrolysis of persimmon tannins were by macroporous resin adsorption.Firstly, purification of Gongcheng persimmon tannin was by macroporous resin XAD16 hydrolysis preliminary.The static adsorption and parsing test of the concentration of the sample solution was 0.5mg / ml, and a concentration of the eluent(ethyl alcohol) was 75%. Dynamic tests was studied on the basis of a static test, to determine the most suitable conditions for adsorption: flow rate was 1ml / min, diameter and height ratio was 1:15, the sample concentration was 0.5mg / ml, the sample volume was 620 ml.Aadsorption amount in XAD16 resin at this time was 165 mg. Of 75% ethanol content of tannin hydrolysis parsed for 112 mg, elution rate was 67.8%.To enhance the purity of the finished hydrolyzed tannins for the further step, XAD16 eluant was purified by macroporous resin XAD1600. XAD1600 resin adsorption conditions was as flows: flow rate was 1ml / min, diameter and height ratio was 1:15, the sample concentration was 0.5mg / ml, the sample volume was 550 ml. And XAD1600 resin adsorption amount at this time was 158 mg.127mg of tannin hydrolysis was parsed by 75% ethanol, elution rate was 80.3%. The purity of tannin hydrolysis obtained by the twice process of separating using macroporous resin was 88.4%, and the purity of hydrolyzed tannin was improved 5.59 times when compared to the persimmon alcohol extract.High content of tannin hydrolyzed were YD1, YD2, YD3, YD4 using the method of gradient elution by different concentrations of ethanol on persimmon tannin hydrolysis, and 29.81 %, 17.39%, 37.26% was of the total eluted tannin hydrolysis each other, purity was 79.9%, 85.4%, 89.8%, 87.1%. respectively.The effect of clearing OH·, O2- · and DPPH·was also studied by hydrolysis of different of components of Gongcheng persimmon tannin. The study showed that OH·Radical scavenging dose relationship displayed in different components of the hydrolysis of tannin for in the concentration range of the set. The ability of YD3 clearing OH· free radicals is higher than gallic acid within 0.6 ~ 1.0mg / m L range, when 1.0mg / m L clearance was 32.82%. In the range of 0.05 ~ 0.20 mg / m L, the ability of YD3 clearing OH· free radicals is higher than YD1, YD2, YD4, slightly lower than gallic acid. When the concentration was 0.20 mg / m L, YD3 could remove 44.12% O2- · free radicals, only 2.66% lower than the acid gallic. In the clearing DPPH·free radicals experiment, the ability of YD3 clearing DPPH· free radicals had high utility. When YD3 concentration was 0.25 mg / m L, the clearance rate was 78.99%. |
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