Ultrasonic-Assisted Semi-Bionic Extraction of Tannins from Wild Persimmon Leaves

摘要

Tannin was extracted from wild persimmon leaves (Diospyros kaki L.f) using the ultrasonic-assisted semi-bionic approach. Infrared spectrum analysis showed that tannins from wild persimmon leaves contain many proanthocyanidin-like substances with 3-O-gallate acyl structure. Free radical scavenging capacity assay showed that the ultrasonic-assisted semi-bionic approach can improve the scavenging activity of tannins on radicals, including OH·, DPPH· and ABTS~(·+). The half maximal inhibitory concentration values were reduced by 0.62, 0.116 and 1.19 mg mL~(-1), respectively, compared with the water reflux extraction method. Experimental results of orthogonal optimization showed that the tannin extraction quantity can reach 226.8 mg g~(-1), which was much higher than the sample obtained without ultrasonic assistance under the following experimental conditions: pH values of 1.8,7.5 and 8.4, respectively; 50 % solvent mass fraction; 35 min extraction time; 50 °C extraction temperature; 300 W ultrasonic power and 30 KHz ultrasonic frequency. These results suggested that this method could increase the activity and extraction yield of tannins.