Characterization of Anthocyanins in Fruit of Kadsura coccinea (Lem.) A.C. Smith by UPLC/Q-TOF-MS Analysis and Evaluation of Stability of the Major Anthocyanins

Anthocyanins in fruit of Kadsura coccinea (Lem.) A.C. Smith were identified by ultra-performance liquid chromatography–quadrupole–time of flight mass spectrometry analysis. Contents of anthocyanins in K. coccinea fruit were determined by HPLC analysis. Colour stability, thermal degradation and antioxidant activity of purified cyanidin-3-xylosylrutinoside were further analysed. As a result, four anthocyanins were identified as delphinidin-3-xylosylrutinoside (1), cyanidin-3-glucosylrutinoside (2), cyanidin-3-xylosylrutinoside (3), and cyanidin-3-rutinoside (4). The individual content of anthocyanins identified was 4.36 ± 0.06, 3.01 ± 0.03, 49.92 ± 0.76 and 2.33 ± 0.04 mg/500 g deseeded K. coccinea fruit, respectively. Cyanidin-3-xylosylrutinoside was stable at pH around 1. Moreover, cyanidin-3-xylosylrutinoside was very sensitive to temperature change and it was even unstable at room temperature. Cyanidin-3-xylosylrutinoside tended to degrade into cyanidin-3-rutinoside, cyanidin-sambubioside and cyanidin at high temperatures. Cyanidin-3-xylosylrutinoside exhibited much better 1,1-diphenyl-2-picrylhydrazyl and 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical scavenging activities than those of butylated hydroxytoluene. However, cyanidin-3-xylosylrutinoside and other three anthocyanin components contributed little to the antioxidant activity of K. coccinea fruit.