Ultrasonic-Assisted Extraction Of Polyphenols From Apple Leaves And Study On Its Antioxidant Activities In Vitro

Apple leaves belong to rosaceous plant, exist in Shaanxi, Shanxi, Hebei, Shandong provinces etc. In 2009, apple crop acreage in Shaanxi reached 8.474 million mu, the amount of apple leaves was also considerable. Apple polyphenols are capable of antioxidant, scavenging free radicals, inhibiting microorganisms, antivirus, anticancer, preventing and curing cardiovascular diseases. To make full use of apple leaves resources, technical conditions of ultrasonic-assisted extraction of polyphenols from apple leaves were researched, the antioxidant activities in vitro and HPLC analysis were also in this study. Main results are as follows:1. The optimal conditions of ultrasonic-assisted extraction of flavonoids from apple leaves were as follows: ethanol concentration 20%, ratio of liquid to solid 51:1(mL:g), extraction temperature 65℃, ultrasonic power 600W, extraction time 20min, and extracted twice, the yield of total flavonoids was 1.98%.2. The optimal conditions of ultrasonic-assisted extraction of polyphenols from apple leaves were as follows: ethanol concentration 20%, ratio of liquid to solid 40:1(mL:g), extraction temperature 75℃, ultrasonic power 600W, extraction time 20min, and extracted twice, the yield of total polyphenols was 4.20%, the purity was 10.07%, phlorizin content reached 6.18%, which was 61.36% of total polyphenols; There was 2.45% phlorizin in apple leaves.3. Macroporous resin X-5 had better adsorption and desorption of polyphenols in apple leaves. The purifying conditions of polyphenols by macroporous resin X-5 were: concentration of feed 3.658mg/mL, pH value 3, feeding volume 5BV, feeding rate 2.0mL/min, 40% ethanol was taken as desorption solution, elution rate 1.0mL/min, elute volume 4BV. After purification, the purity of polyphenols was 38.55%, phlorizin content was 32.84%, which was 85.16% of total polyphenols.The absorbing process of apple leaves polyphenols by macroporous resin X-5 was an exothermic course, belonged to favourable adsorption, it accorded with Langmuir isothermal model and Freundlich isothermal model.4. Apple leaves extract had good antioxidant activities in vitro, compared with tea polyphenols, it held stronger scavenging activities on·OH and O2-·, comparative reducing power, feeblish scavenging activities on DPPH and NO2-. After purification, the ability of scavenging DPPH and NO2- was enhanced, the ability of scavenging·OH and O2-·was weakened ratherish.5. Refining apple leaves polyphenols by Sephadex LH-20, 80% ethanol was taken as desorption solution, the purity of polyphenols in refined extract was 52.02%, phlorizin content reached 47.61%, which was 91.51% of total polyphenols.