Optimization of Ultrasonic Extraction of Flavonoids from ZelkovaschneiderianaLeaves by Box-Behnken

On August 26, 2017, collections were implemented on1-3 leaves of 1-yearZelkovaschneiderianain greenhouse for experiment on extraction of flavonoids.Optimization of ultrasonic extraction of flavonoids was designed by box-behnkenwith three factors at three levels.The result demonstrated that the best technology for extraction was as follows, ethanol concentration of 63%, liquidratio of 31:1mL?g-1, extraction time of 1.7 hour, with the yield of flavonoids of (31.067±0.11)mL?g-1.Preliminary identification of extracted flavonoids showed flavones, flavonoids with adjacent two phenolic hydroxyl structures, and compounds with two phenol hydroxyl groups or 3-OH, 4=O or 5-OH, 4=O, and possible flavonoils, dihydroflavones and dihydroflavonols, but no chalcone and aurones.