以不同贮藏年份康砖茶为试验材料，检测其儿茶素、没食子酸和茶色素含量，测定其多酚提取物还原铁离子的能力、清除DPPH和ABTS自由基的能力，比较其抗氧化活性。结果表明：随着贮藏年份的增加，康砖茶总黄酮、茶褐素和没食子酸含量呈显著增加的趋势（p<0.05）。多酚提取物FRAP·EC50（8.28 μg/mL~14.55 μg/mL）显著高于DPPH·EC50（4.26 μg/mL~4.99 μg/mL）和ABTS EC50（5.14 μg/mL~5.50 μg/mL），且DPPH EC50显著低于ABTS EC50（p<0.05）。随着贮藏年份的增加，DPPH EC50显著降低；FRAP EC50先显著增加，后显著降低（p<0.05）。贮藏期6年（YA2010）ABTS EC50显著低于其他年份（p<0.05）。贮藏时间为15年（YA2001）和23年（YA1993）的康砖茶还原铁离子的能力和清除DPPH自由基的能力高于其他年份康砖茶。相关性分析表明，FRAP EC50和DPPH·EC50均与没食子酸、茶褐素呈显著负相关（p<0.05）；ABTS·EC50与没食子酸呈显著正相关（p<0.05）。因此，康砖茶多酚提取物具有抗氧化活性。贮藏时间越长，还原能力和清除DPPH自由基能力越强，但清除ABTS自由基的能力与贮藏时间没有明显的规律性。

Five aged Kang brick teas were used as analytical materials to comparatively analyze its tea polyphenols, catechins and tea pigments. EC50 analysis of antioxidant activities were determined of FRAP, DPPH· and ABTS·. The results showed that contents of the components increased significantly (p<0.05), including catechins, gallic acid, theabrownin and flavonoids during storage period. The median effect concentration (EC50) of FRAP reached from eight point twenty-eight μg/mL to fourteen point fifty-five μg/mL, which were higher than that of DPPH· (4.26 μg/mL~4.99 μg/mL) and ABTS· (5.14 μg/mL~5.50 μg/mL) (p<0.05). EC50 of DPPH· was lower than that of ABTS· (p<0.05). With the prolongation of storage period, DPPH·EC50 decreased significantly, and FRAP EC50 increased and next decreased significantly. ABTS·EC50 was significantly lower than other samples in storage period of 6 years. The ability of reducing iron ion and scavenging DPPH· radical of the extracts stored for 15 years and 22 years was significantly higher than that of other years. The correlation analysis showed that EC50 of FRAP and EC50 of DPPH were negatively correlated with gallic acid and theanine (p<0.05), and the EC50 of ABTS was positively correlated with gallic acid (p<0.05). Therefore, the polyphenol extract of Kang bricks tea has antioxidant activity. The longer the storage time is, the stronger the ability of reducing and scavenging DPPH· radical are, but there is no obvious relavance between the ability of removing ABTS and the storage time.

国家自然科学基金(31600560)；省农村科技领域项目（2017A020208020）；国家茶叶产业技术体系项目(CARS1909B)