Comparison of total phenol content and antioxidant activity of herbal infusions with added Stevia reabaudiana Bertoni

Abstract Antioxidant capacity (AC) was determined by the ABTS method and DPPH, and total phenol content (TPC) in dehydrated plant material, in infusions and in residues (plant material after preparing the infusion) of white, black, red, green, spearmint, stevia, lemon grass and chamomile teas to which stevia leaves were added or not added; addition of processed stevia powder was also tested. Three independent experiments were set up: with dehydrated plant material, with infusions and with residues. For the case of dehydrated plant material, white tea had the highest TPC (10813.5 mg GAE/100g) and AC by the ABTS method (1183.3 µM TE/g) and DPPH method (1525.0 µM TE/g). In infusions, black tea had higher TPC (180.82 µg GAE/ml) and AC by the methods ABTS and DPPH (0.6114 and 2.5983 µM TE/ml, respectively). In residues, TPC was higher in white tea, while green tea had the highest AC values. AC of dehydrated plant material increased when stevia leaves were added, according to the DPPH and ABTS methods, but not in residues by ABTS. Addition of stevia leaves in infusions increased AC in white, lemon grass, chamomile and stevia teas by the ABTS method and in spearmint, black, red, and green teas with the DPPH method.

摘要：本研究采用ABTS法与DPPH法，对添加或未添加甜叶菊叶的白茶、红茶、红茶、绿茶、留兰香薄荷茶、甜叶菊茶、香茅茶及洋甘菊茶的脱水植物材料、浸液及制备浸液后的残渣中的抗氧化能力（Antioxidant Capacity, AC）与总酚含量（Total Phenol Content, TPC）进行了测定；此外还开展了加工甜叶菊粉添加效果的测试。本研究设置了三组独立实验，分别以脱水植物材料、浸液及残渣为测试对象。在脱水植物材料组中，白茶的总酚含量达到最高（10813.5 mg 没食子酸当量（Gallic Acid Equivalent, GAE）/100g），且通过ABTS法（1183.3 µM Trolox当量（Trolox Equivalent, TE）/g）与DPPH法（1525.0 µM TE/g）测得的抗氧化能力也均为各组最高。在浸液组中，红茶的总酚含量为180.82 µg GAE/ml，且ABTS法与DPPH法测得的抗氧化能力分别为0.6114与2.5983 µM TE/ml，均高于其他茶样。在残渣组中，白茶的总酚含量最高，而绿茶的抗氧化能力数值达到峰值。根据DPPH法与ABTS法的检测结果，添加甜叶菊叶可提升脱水植物材料的抗氧化能力，但ABTS法未检测到残渣组的抗氧化能力出现显著提升。在浸液中添加甜叶菊叶后，ABTS法检测显示白茶、香茅茶、洋甘菊茶及甜叶菊茶的抗氧化能力得以提升；而DPPH法检测则证实留兰香薄荷茶、红茶、红茶及绿茶的抗氧化能力得到增强。