茶叶提取物体外抗氧化活性与其功能性成分含量的相关性研究

分别选取信阳毛尖、红碎茶、普洱熟茶为典型不发酵、全发酵及后发酵茶种,测定其醇提物及水提物中的主要成分,并以氧自由基的吸收能力(ORAC)和DPPH自由基的清除能力为指标,比较各样品体外抗氧化活性,采用功能化合物重组模型,探究茶叶提取物抗氧化活性的主要贡献物质。结果表明:茶叶醇提物中茶多酚、咖啡因及醇溶蛋白的含量较高,其ORAC值及DPPH自由基清除能力均较对应水提物强;茶叶水提物功能性组分以茶多酚、茶多糖及氨基酸为主,都具有一定的抗氧化活性。其中茶多酚含量,尤其是酯型儿茶素(ECG和EGCG)含量是影响茶叶提取物抗氧化活性的主要因素。重组试验结果表明,儿茶素和没食子酸是不发酵茶(信阳毛尖)提取物的主要抗氧化组分,但并不是红碎茶、普洱熟茶等发酵茶中的主要抗氧化成分。

Study on the relationship between the composition of tea extracts and its in vitro antioxident activity

In this study, Maojian, crushed black tea and zymic Pu''er tea were chosen as representative of non-fermented, fully-fermented and post-fermented tea, respectively. The composition profiles of ethanol/water extracts were compared, and the antioxidant activities in vitro were detected by oxygen radical absorbance capacity (ORAC) and DPPH assay. In order to confirm the contribution of each key functional contributors, recombination model of antioxidant compounds in tea have been built and studied. The results showed that ethanol extracts contained higher contents of tea polyphenol, caffeine and prolamin, and higher antioxidant activities detected by ORAC and DPPH assay, while higher amounts of tea polysaccharide, gallic acid and theanine were found in water extract. Correlation analysis showed that antioxidant capacities of tea extracts were mostly influenced by ester catechins, such as ECG and EGCG. The results of recombination test showed that catechins and gallic acid were the major compounds responsible for antioxidant activity of Maojian extract, whereas other bioactive compounds might also exist in fermented tea, i.e., crushed Black tea and zymic Pu''er tea.