Er Sheng Gong1, Bin Li2, Binxu Li2, Natalia S Podio3, Hongyu Chen4, Tong Li5, Xiyun Sun2, Ningxuan Gao2, Wenlong Wu6, Tianran Yang7, Guang Xin2, Jinlong Tian2, Xu Si2, Changjiang Liu2, Jiyue Zhang2, Rui Hai Liu5. 1. School of Public Health and Health Management, Gannan Medical University, Ganzhou, 341000, China. 2. College of Food Science, Key Laboratory of Healthy Food Nutrition and Innovative Manufacturing of Liaoning Province, National R&D Professional Center for Berry Processing, Shenyang Agricultural University, Shenyang, 110866, China. 3. Instituto de Ciencia y Tecnología de Alimentos Córdoba (ICYTAC), CONICET, ISIDSA-SECYT-UNC, University City, Bv. Filloy s/n, SECYT, 5000 Córdoba, Argentina. 4. Institute of Edible Fungi, Shanghai Academy of Agricultural Science, Shanghai, 201403, China. 5. Department of Food Science, Cornell University, Ithaca, 14853-7201, United States. 6. Institute of Botany, Jiangsu Province and Chinese Academy of Sciences, Nanjing, 210014, China. 7. Office of Teaching and Global Affairs, South China University of Technology, Guangzhou, 510641, China.
Abstract
BACKGROUND: Free fractions of different blackberry varieties' extracts are high in phenolic compounds with antioxidant activities. However, the phenolic profiles and antioxidant activities against peroxyl radicals of bound fractions of different blackberry varieties' extracts have not been previously reported. In addition, what the key antioxidant phenolic compounds are in free and bound fractions of blackberry extracts remain unknown. This study aimed to investigate the phenolic profiles and antioxidant activities of free and bound fractions of eight blackberry varieties' extracts and reveal the key antioxidant phenolic compounds by boosted regression trees. RESULTS: Fifteen phenolics (three anthocyanins, four flavonols, three phenolic acids, two proanthocyanidins, and three ellagitannins) were identified in blackberry by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Ferulic acid, ellagic acid, procyanidin C1, kaempferol-O-hexoside, ellagitannins hex, and gallic acid were major bound phenolics. Bound fractions of eight blackberry varieties' extracts were high in phenolics and showed great antioxidant activity. Boosted regression trees analysis showed that cyanidin-3-O-glucoside and chlorogenic acid were the most significant compounds, contributing 48.4% and 15.9% respectively to the antioxidant activity of free fraction. Ferulic acid was the most significant antioxidant compound in bound fraction, with a contribution of 61.5%. Principal component analysis showed that Kiowa was the best among the eight varieties due to its phenolic profile and antioxidant activity. CONCLUSION: It was concluded that blackberry varieties contained high amounts of bound phenolics, which confer health benefits through reducing oxidative stress. Ferulic acid was the key compound to explain the antioxidant activities of bound fractions.
BACKGROUND: Free fractions of different blackberry varieties' extracts are high in phenolic compounds with antioxidant activities. However, the phenolic profiles and antioxidant activities against peroxyl radicals of bound fractions of different blackberry varieties' extracts have not been previously reported. In addition, what the key antioxidant phenolic compounds are in free and bound fractions of blackberry extracts remain unknown. This study aimed to investigate the phenolic profiles and antioxidant activities of free and bound fractions of eight blackberry varieties' extracts and reveal the key antioxidant phenolic compounds by boosted regression trees. RESULTS: Fifteen phenolics (three anthocyanins, four flavonols, three phenolic acids, two proanthocyanidins, and three ellagitannins) were identified in blackberry by ultra-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry. Ferulic acid, ellagic acid, procyanidin C1, kaempferol-O-hexoside, ellagitannins hex, and gallic acid were major bound phenolics. Bound fractions of eight blackberry varieties' extracts were high in phenolics and showed great antioxidant activity. Boosted regression trees analysis showed that cyanidin-3-O-glucoside and chlorogenic acid were the most significant compounds, contributing 48.4% and 15.9% respectively to the antioxidant activity of free fraction. Ferulic acid was the most significant antioxidant compound in bound fraction, with a contribution of 61.5%. Principal component analysis showed that Kiowa was the best among the eight varieties due to its phenolic profile and antioxidant activity. CONCLUSION: It was concluded that blackberry varieties contained high amounts of bound phenolics, which confer health benefits through reducing oxidative stress. Ferulic acid was the key compound to explain the antioxidant activities of bound fractions.