Optimization Extracting Process and Comparative Study of Compounds of Polyphenol in Mulberry Leaf
The polyphenol extract of mulberry leaves was prepared by ultrasonic-assisted method after 1 h ethanol extraction.The extraction conditions were optimized by response surface method with the yield of polyphenol as the index.The antioxidant capacity and polyphenol retention rate of mulberry leaf polyphenol extract and complex(mulberry leaf extract mixed with Mongolian oak vinegar)were compared.The results showed that the optimal extraction technology was as follows:extraction power was 200 W,liquid-solid ratio was 15∶1(mL∶g),ultrasonic time was 49 min,ultrasonic temperature was 61℃,ethanol volume fraction was 64％,and the actual extraction rate of polyphenols was 3.087％.The half-effect concentration(EC50)of the extract on the total reducing capacity was 4.67 g/L,and the half-inhibitory concentration(IC50)on hydroxyl and 1,1-diphenyl-2-picrylhydrazyl(DPPH)radical were 1.2 g/L and 0.065 g/L,respectively.The EC50 of the complex for total reduction capacity was 5.91 g/L,and the IC50 for DPPH radical was 0.152 g/L.The polyphenol retention rates of extracts and compounds were the highest at 30 ℃,pH 3 and dark conditions.With the increase of temperature,pH value and light treatment,the polyphenol retention rates were greatly reduced.The antioxidant capacity and polyphenol retention rate of the extract were stronger than those of the complex,there was no synergistic effect between the extract and wood vinegar.
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