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Assessment of the bioactive phenolic composition of Acer truncatum seed coat as a byproduct of seed oil

Fan, Hang, Sun, Liwei, Yang, Lingguang, Zhou, Jinchi, Yin, Peipei, Li, Ke, Xue, Qiang, Li, Xiang, Liu, Yujun
Industrial crops and products 2018 v.118 pp. 11-19
2,2-diphenyl-1-picrylhydrazyl, 2,5-dihydroxybenzoic acid, Acer truncatum, acetone, antioxidant activity, antioxidants, byproducts, epicatechin, ethanol, manufacturing, naringenin, proanthocyanidins, procyanidins, seed coat, seed oils, tannins, wastes
Acer truncatum seed coat is generally abandoned as waste during the process of manufacturing seed oil due to a lack of knowledge of the phytochemical composition of this byproduct. It is well known that brown-colored seed coat is rich in polyphenols; therefore, we investigated the bioactive phenolic composition of A. truncatum seed coat in this study. To obtain an extract containing most bioactive phenolic compounds, extractions in six solutions (water, 40% ethanol, 70% ethanol, 100% ethanol, 70% acetone, and 100% acetone) were compared for their yields, phenolic contents, and antioxidant activities. The 70% ethanol extract, which had the highest yield at 76.38 g extract/100 g dry matter, showed the highest levels of total phenols, total flavonoids, total tannins, and condensed tannins, as well as the highest DPPH and ABTS+ scavenging activities. UPLC-QTOF-MS analyses resulted in identification of 13 phenolic compounds in the 70% ethanol extract, among which five compounds, gentisic acid, naringenin, epicatechin, procyanidin tetramer, and procyanidin pentamer, were identified for the first time in A. truncatum. Five flavonoids and four procyanidin oligomers were the dominant phenolic components, comprising 63.27% and 31.02% of the 13 phenolic compounds, respectively. Correlation analyses revealed that flavonoids and tannins were the major factors responsible for the high antioxidant activities, suggesting that these two components of A. truncatum seed coat could be developed as alternative antioxidants. This is the first known report on the phenolic composition of seed coats in the genus Acer.