Determination of flavonols in green and black tea leaves and green tea infusions by high-performance liquid chromatography |
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| Affiliation: | 1. Institute of Pharmaceutical Sciences, Department of Pharmacognosy, University of Graz, Universitätsplatz 4, 8010 Graz, Austria;2. Institute of Pharmaceutical Sciences, Department of Pharmaceutical Chemistry, University of Graz, Universitätsplatz 1, 8010 Graz, Austria;3. Department of Neuroscience, Biomedical Center, Uppsala University, Box 593, 75124 Uppsala, Sweden;4. Department of Chemistry, Ångström Laboratories, Uppsala University, Box 523, 75120 Uppsala, Sweden;1. Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, Tea Research Institute, Chinese Academy of Agricultural Sciences, 9 Meiling South Road, Hangzhou, Zhejiang 310008, People’s Republic of China;2. Agilent Technologies (China) Limited, 3 Wangjing North Road, Chaoyang District, Beijing 100102, People’s Republic of China;3. College of Horticulture and Forestry Science, Huazhong Agricultural University, 1 Shizishan Street, Hongshan District, Wuhan, Hubei 430070, People’s Republic of China;4. Graduate School of Chinese Academy of Agricultural Sciences, 12 Zhongguancun South Street, Haidian District, Beijing 100081, People’s Republic of China;1. College of Food Science, South China Agricultural University, 483 Wushan Street, Tianhe District, Guangzhou 510642, PR China;2. Drink Plant Research Institute, Tea Research Center, Guangdong Academy of Agricultural Sciences, 6 Dafeng Road, Tianhe District, Guangzhou, Guangdong 510640, PR China;1. Tea Research Institute Chinese Academy of Agricultural Sciences, National Engineering & Technology Research Center for Tea Industry, Key Laboratory of Tea Biology and Resources Utilization, Ministry of Agriculture, 9 South Meiling Road, Hangzhou 310008, China;2. Graduate School of Chinese Academy of Agricultural Sciences, Beijing 100081, China;3. Food Processing and Quality, Innovative Food System, Natural Resources Institute Finland (Luke), 02150 Espoo, Finland;4. State Key Laboratory of Tea Plant Biology and Utilization, Anhui Agricultural University, Hefei, China;5. Wuyuan County Jufangyong Tea Industry Limited Company, Shangrao 333200, China |
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| Abstract: | Tea flavonols are potent antioxidants and make up 2–3% of the water-soluble solids from tea leaves. In this paper, the conditions necessary for hydrolysing and analysing flavonols in tea leaves and tea infusions are optimised and an isocratic elution system for the determination of the hydrolysed flavonols by high-performance liquid chromotography is presented. Aqueous ethanol was selected as the best solution for hydrolysing flavonoids in tea leaves. The contents of flavonols on a dry weight base in green tea leaves ranged from 0.83–1.59, 1.79–4.05, and 1.56–3.31 g/kg, and in black tea leaves from 0.24–0.52, 1.04–3.03, and 1.72–2.31 g/kg for myricetin, quercetin, and kaempferol, respectively. It was observed that the particle size of ground tea leaves significantly influenced the yield of flavonols. The contents of flavonols in different green tea infusions are given. |
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