Ultrasound-assisted ionic liquids extraction of carotenoids from Xinjiang apricots and evaluation of their antioxidant potential

Xinjiang apricot is favoured by consumers because of its distinctive aroma, high nutritive value, and abundant functional active substances. Carotenoids of apricot are efficient antioxidants that can protect the human body from free radical attack. However, the extraction, quantification, and antioxidant activity of carotenoids from Xinjiang apricots have not been reported. In this work, ultrasound-assisted ionic liquid (ILs) extraction and optimisation of carotenoids from Xinjiang apricots and to evaluate their antioxidant potential. Based on Box-Behnken design (BBD), the best conditions were IL/ethanol (RIL/E) ratio of 1 : 2, solid-liquid ratio (RS/L) of 1 : 3, extraction time of 17 min and number of extractions of 3. The content of carotenoid extracted by ultrasonic-assisted [Bmim][BF4] ILs was 32.98 ± 0.27 μg.g-1 that of traditional extraction method was 25.05 ± 0.35 μg.g-1. Moreover, ultrasonic-assisted ILs extraction technology can shorten the extraction time, simplify the extraction steps and increase the extraction amount. Meanwhile, in order to recover and reuse ILs, ILs-ethanolic solution was frozen at temperatures lower than -80 °C, allowing the ILs precipitation and separation from the ethanol solution. Meantime, the antioxidant potential of five Xinjiang apricot varieties were evaluated by DPPH (2,2-diphenyl-1-picrylhydrazyl) and ABTS [2,2'-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid)] assays in vitro and analysed by UV-vis spectroscopy and Raman spectroscopy. The results showed Shushanggan apricot has the highest carotenoid content and the strongest antioxidant activity. In conclusion, this research further proves the advantage of ultrasonic-assisted ILs in carotenoid extraction and the potential to obtain valuable carotenoids from the apricot industries.