Department of Analytical Chemistry, Aragon Institute of Engineering Research I3A, CPS-University of Zaragoza , Torres Quevedo Building, María de Luna Street 3, E-50018 Zaragoza, Spain.
J Agric Food Chem. 2012 Oct 3;60(39):9842-9. doi: 10.1021/jf302477y. Epub 2012 Sep 25.
The oxygen radical absorbance capacity (ORAC) method was used to characterize the antioxidant capacity of natural extracts of green tea, green coffee, and grapefruit. These natural extracts were incorporated into a plastic film layer, which was subsequently subjected to a free radical gas stream in order to determine the antioxidant capacity directly in the active film. The green tea extract (GTE) afforded the strongest antioxidant activity. To identify the active compounds in the extract, concentration of the diverse catechins in samples were determined by HPLC-UV analysis. The results showed that the content of catechins in the GTE is around 77% (w/w), the major components being (-)-epigallocatechin gallate, (-)-epicatechin gallate, and (-)-epicatechin. A variation in the concentration profile of catechins was detected during the oxidation process. The chromatographic study demonstrated that (-)-gallocatechin, (-)- epigallocatechin, (+)-catechin, and (-)-catechin gallate exhibited the most radical scavenging.
采用氧自由基吸收能力（ORAC）法对绿茶、绿咖啡和葡萄柚的天然提取物的抗氧化能力进行了表征。将这些天然提取物掺入到塑料薄膜层中，随后将其暴露于自由基气流中，以便直接在活性薄膜中测定抗氧化能力。绿茶提取物（GTE）具有最强的抗氧化活性。为了鉴定提取物中的活性化合物，通过 HPLC-UV 分析确定了样品中各种儿茶素的浓度。结果表明，GTE 中的儿茶素含量约为 77%（w/w），主要成分是（-）-表没食子儿茶素没食子酸酯、（-）-表儿茶素没食子酸酯和（-）-表儿茶素。在氧化过程中检测到儿茶素浓度分布的变化。色谱研究表明，（-）-没食子儿茶素、（-）-表没食子儿茶素、（+）-儿茶素和（-）-儿茶素没食子酸酯表现出最强的自由基清除能力。
