Extraction, Composition, and Antioxidant Activity of Flavonoids from Xanthoceras sorbifolium Bunge Leaves

Background Xanthoceras sorbifolium Bunge leaves (XLs) are valuable resources rich in phytochemicals, especially in flavonoids, but they are rarely exploited and utilized. Objective The purpose of this paper is to reduce the waste of XLs resources (usually used as agricultural waste) and extract the high added value of active ingredients from XLs. Methods The extraction of flavonoids from XLs using ultrasonic-assisted extraction (UAE) was reported. Response surface methodology (RSM) was used to adopt different ultrasonic conditions such as ethanol concentration, liquid:solid ratio, and ultrasonic power. In addition, the chemical structures were identified using ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) and HPLC. Results Response surface analysis indicated the optimal level of ethanol concentration, liquid:solid ratio, and ultrasonic power as 71.49%, 13.87 mL/g, and 157.49 W respectively for the maximum response of total flavonoids (5.52 +/- 0.23%), which fitted well with the predicted value (5.68 +/- 0.17%). In addition, the extracts from XLs exhibited potent antioxidant activity using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2 '-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) ammonium salt (ABTS). Conclusion The potent antioxidant activity of flavonoids from XLs is beneficial for their application in the food and drug industry, which will facilitate the rise of the added value of the flavonoids from XLs.