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

BACKGROUND
Xanthoceras sorbifolium Bunge leaves (XLs) were valuable sources being rich in phytochemicals, especially in flavonoids, but almost no exploitation.


OBJECTIVE
The purpose of this paper is to reduce the waste of industrial by-products and develop the high added value of active ingredients from XLs.


METHOD
The extraction of flavonoids from XLs using ultrasonic-assited extraction (UAE) was reported. Response surface methodology (RSM) was used to optimize the relative parameters 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 high performance liquid chromatography (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 was fitted well with the predicted value (5.68 ± 0.17%). In addition, the extracts from XLs exhibited potent antioxidant activity by 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 was beneficial for their application in the food and drug industry, which will facilitate the rise of the added value of the by-products XLs.


HIGHLIGHTS
Myricetin, rutin, and epicatechin which may be responsible for the antioxidant activity of the extracts from XLs were confirmed by UPLC-MS/MS and HPLC analysis. Thus, the extracted flavonoids can be used as a natural antioxidant additive to food products.