Moldoveanu Serban C, Oden Ross
R. J. Reynolds Tobacco Co., 950 Reynolds Blvd., Winston-Salem, North Carolina 27105, United States.
ACS Omega. 2021 Apr 7;6(15):9982-9988. doi: 10.1021/acsomega.0c05818. eCollection 2021 Apr 20.
The present study measured the antioxidant properties of 15 commercial tea samples as expressed by the oxygen radical absorbance capacity (ORAC) hydro, ORAC lipo, and ferric reducing antioxidant power (FRAP) indexes. The main antioxidant compounds known to be present in tea are several catechins and catechin gallates, gallic acid, theaflavin and some theaflavin gallates, and theogallin. In this study, only gallic acid and the four most common catechins (epicatechin, epigallocatechin, epicatechin gallate, and epigallocatechin gallate) were analyzed in the tea samples. In addition, caffeine levels were measured. The ORAC and FRAP values for these compounds were also determined. The levels of theaflavin, theaflavin gallates, and theogallin were not measured since these compounds are present at relatively low levels in tea. The ORAC (and FRAP) indexes for each tea sample were also calculated based on the content of individual antioxidant compounds and their ORAC and FRAP indexes. Correlations between the experimental ORAC (and FRAP) and the calculated values were further obtained. The correlations were poor, with = 0.3657 for ORAC hydro, = 0.2794 for ORAC lipo, and = 0.6929 for FRAP. The poor correlation between the overall catechin content and the experimental ORAC values in tea infusions was previously reported in the literature. The present study directly calculated the expected ORAC index from individual antioxidant components and reached the same result of poor correlation. For FRAP values, no comparison was previously reported in the literature. The poor correlations were not well explained, indicating that the cause of the antioxidant character of tea is more complex than simply produced by the main catechins.
本研究测定了15种市售茶叶样品的抗氧化性能，用羟基氧自由基吸收能力（ORAC hydro）、脂质氧自由基吸收能力（ORAC lipo）和铁还原抗氧化能力（FRAP）指数来表示。已知茶叶中存在的主要抗氧化化合物有几种儿茶素和儿茶素没食子酸酯、没食子酸、茶黄素和一些茶黄素没食子酸酯，以及没食子儿茶素。在本研究中，仅对茶叶样品中的没食子酸和四种最常见的儿茶素（表儿茶素、表没食子儿茶素、表儿茶素没食子酸酯和表没食子儿茶素没食子酸酯）进行了分析。此外，还测定了咖啡因含量。还测定了这些化合物的ORAC和FRAP值。由于茶黄素、茶黄素没食子酸酯和没食子儿茶素在茶叶中的含量相对较低，因此未对其进行测定。还根据各抗氧化化合物的含量及其ORAC和FRAP指数计算了每个茶叶样品的ORAC（和FRAP）指数。进一步获得了实验ORAC（和FRAP）与计算值之间的相关性。相关性较差，ORAC hydro的相关系数r = 0.3657，ORAC lipo的相关系数r = 0.2794，FRAP的相关系数r = 0.6929。文献中先前报道过茶浸液中总儿茶素含量与实验ORAC值之间的相关性较差。本研究直接从各个抗氧化成分计算出预期的ORAC指数，得到了相关性较差的相同结果。对于FRAP值，文献中先前未报道过比较情况。相关性较差的原因尚不清楚，这表明茶叶抗氧化特性的成因比单纯由主要儿茶素产生的情况更为复杂。
