Preparation of Blueberry Anthocyanin Glycosides and Aglycones and Their Antioxidant Activity
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Abstract:
Several studies have noted the high antioxidant activity of anthocyanins in blueberry fruits. However, there have been no studies on the structural form (glycosides or aglycones) of anthocyanins providing the highest antioxidant activity. In the present study, a combination of extraction (solid-liquid and liquid-liquid) and column chromatography was used for preparing blueberry anthocyanin glycosides and aglycones, and ultraviolet-visible (UV-vis) spectroscopy and high-performance liquid chromatography (HPLC) were used to determine the purity and structure of anthocyanin extracts. The antioxidant activities of two anthocyanin samples were evaluated by the hydroxyl radical (?OH), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) free radical scavenging activities. After acid-ethanol solid-liquid extraction, ethyl acetate liquid-liquid extraction, and chromatographic separation on macroporous resins, the anthocyanin glycoside extract was obtained with a purity of 59.46%, and 14 glycoside monomers were identified. Based on this finding, the purified anthocyanin glycoside extract underwent acid hydrolysis and chromatographic separation to yield blueberry anthocyanin aglycone extract with a purity of 50.58%, and five aglycone monomers were identified. The antioxidant capacity of anthocyanin aglycones was significantly higher (p<0.05) than that of glycosides, and was 1.31 to 1.72 times that of the Trolox reference. The results of the present study indicate that transforming anthocyanin glycosides into aglycone forms improve their antioxidant activity.
