| The growing region of purple sweet potato is very widely distributed in China.The byproduct of purple sweet potato is its stems and leaves,which contains certain amount of flavonoids.Numerous studies at home and abroad have shown that total flavonoids have the function of antioxidation,free eliminating radicals,anti-aging,anti-tumor and anti-cardiovascular diseases.At present,there are relatively few studies on total flavonoids in the leaves of purple sweet potato,and the extraction and development needs to improve.The stems and leaves of purple sweet potato are mainly used as livestock feed or waste,and this phenomenon is commonly existed in northeast China.The comprehensive utilization of a large number of potential flavonoids in the leaf of purple sweet potato can not only maximize the economic value,but also is favorable to protect the environment.The purple potato stem leaf was used as raw material in this experiment,the best extraction method and the optimum process were determined,the effects of various factors on the yield of flavonoids in the ultrasonic and microwave methods were investigated respectively.and then process was optimized by response surface experiment,then we chose he macroporous resin purification flavonoids,and identified by high performance liquid extract of main ingredients,finally to explore the oxidative stability of the main components of extracts were identified by high performance liquid chromatography,and the antioxidant properties of flavonoids were studied in detail.The main conclusions are as follows:(1)By single factor experiment and response surface optimization experiment,total flavonoids in yield as examining index,the optimum extraction method for ultrasonic method,the best extraction technology conditions is were obtained,with the liquid ratio of which is the liquid ratio is 18:1(mL/g),ultrasonic time 50 min,ultrasonic power 200 w,ethanol volume fraction of 75%,under the optimal conditions for 5 times test,the flavonoids yield is 3.46%.(2)The resin of AB-8 was selected to purify the purple potato leaf flavonoids,through static single factor experiment and dynamic single factor experiment,the optimum purification conditions are as follows: the optimized sample weight 50 mL,water volume 80 mL,elution volume of 90 mL,the upper sample flow rate of 1.5 mL/min,and the upper sample concentration1.0 mg/mL,flow rate of 1.5 mL/min,purity of 85.67% after total flavonoids purification.(3)the main components of extract in the stem and leaf of purple sweet potato were identified,and through the analysis of high performance liquid phase,the total flavonoids in the leaves of potato stem and leaf were found to contain isorhamnetin rutin vitexin and hyperoside.(4)The antioxidant activity of total flavonoids in purple sweet potato stem leaves was studied with the same Vc as the same concentration.When the mass concentration reached 0.5mg/mL,the DPPH free radical clearance rate reached 68.13%.The removal rate of hydroxyl radical was 61.74%,and the clearance rate of superoxide anion was 66.27%.The results showed that the total flavonoids of purple potato stem leaves could be a good substitute for Vc. |
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