The present work aims to evaluate the relation between the antioxidant activities and phenolic compound contents of two tea samples (green and black) mixed with or without sweeteners (sucrose or aspartame). The aqueous extracts were screened for total polyphenol and flavonoids contents. Antioxidant activities of extracts were tested using 2, 2-diphenyl-1-picrylhydrazyl (DPPH) radical method and 2, 2′-azino-bis [ethylbenzthiazoline-6-sulfonic acid] (ABTS) methods using butylated hydroxyl anisole as standard compound. In addition, we identified polyphenols compounds using high performance liquid chromatography (HPLC). The results indicated that the antioxidant activity was higher against ABTS radical more than DPPH radical. Also, there is positive correlation between the antioxidant activity and phenolic compounds content presented in water extracts of tea samples. The results also indicated that addition of table sugar to green tea significantly decreased the antioxidant activity (from 95.8% to 90.6% with 4.0% sucrose). However, the same table sugar in black tea increased the antioxidant activity (from 87.0% to 91.9% with 4.0% sucrose). The analysis using HPLC showed that caffeine was the most predominant individual compounds in green and black tea without and with 1.0% sucrose (6081.8, 8772.1, 6474 and 3755 µg/100g, respectively). However, cinnamic acid showed the lowest content in the same tea samples (0.21, 0.25, 0.19 and 0.18 µg/100g respectively). Pyrogallol, catechol, epicatechin, ellagic, protocatchuic were significantly higher in green tea than in black tea.

本工作旨在评估混合或不混合甜味剂（蔗糖或阿斯巴甜）的两种茶样品（绿色和黑色）的抗氧化活性与酚类化合物含量之间的关系。筛选水提取物的总多酚和类黄酮含量。提取物的抗氧化活性使用2,2-二苯基-1-吡啶并肼基（DPPH）自由基方法和2,2'-叠氮基双[乙基苯并噻唑啉-6-磺酸]（ABTS）方法（以丁基化羟基茴香醚为标准化合物）进行测试。此外，我们使用高效液相色谱（HPLC）鉴定了多酚化合物。结果表明，抗ABTS自由基的抗氧化活性高于DPPH自由基。也，茶水提取物中的抗氧化活性与酚类化合物含量呈正相关。结果还表明，向绿茶中添加食用糖显着降低了抗氧化活性（使用4.0％蔗糖时，其抗氧化活性从95.8％降至90.6％）。但是，红茶中相同的食糖可提高抗氧化活性（蔗糖为4.0％时从87.0％增至91.9％）。HPLC分析表明，咖啡因是绿茶和红茶中最主要的单个化合物，不含和含1.0％蔗糖（分别为6081.8、8772.1、6474和3755 µg / 100g）。但是，肉桂酸在相同的茶样品中含量最低（分别为0.21、0.25、0.19和0.18 µg / 100g）。绿茶中的邻苯三酚，邻苯二酚，表儿茶素，鞣花，原香的含量显着高于红茶。