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，测定了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、浸提液与浸提残渣（制备浸提液后的植物残余物）的抗氧化能力（Antioxidant capacity, AC）及总酚含量（total phenol content, TPC）；同时考察了加工甜叶菊粉的添加效应。本研究设置三组独立实验，分别以脱水植物材料、浸提液与浸提残渣为研究对象。针对脱水植物材料样本，白茶的总酚含量最高，达10813.5 mg GAE/100g，其ABTS法与DPPH法测得的抗氧化能力分别为1183.3 µM TE/g与1525.0 µM TE/g。在浸提液样本中，红茶的总酚含量为180.82 µg GAE/ml，ABTS法与DPPH法测得的抗氧化能力分别为0.6114 µM TE/ml与2.5983 µM TE/ml，均为所有样本中的最高值。在浸提残渣样本中，白茶的总酚含量最高，而绿茶的抗氧化能力最强。经DPPH法与ABTS法检测，添加甜叶菊叶可提升脱水植物材料的抗氧化能力，但ABTS法检测结果显示，添加甜叶菊叶对浸提残渣的抗氧化能力无显著提升效果。在浸提液中添加甜叶菊叶，可通过ABTS法提升白茶、香茅茶、洋甘菊茶及甜叶菊茶的抗氧化能力，通过DPPH法提升留兰香薄荷茶、红茶、红茶及绿茶的抗氧化能力。