不同类型茶叶体外抗氧化能力的比较分析

Comparative Analysis on Antioxidant Capacities of Different Types of Fermented Teas in vitro

选用4类发酵类型共16种茶叶,以酒石酸亚铁法测定其茶多酚含量,高效液相色谱(HPLC)法测定儿茶素、茶黄素和没食子酸含量,三氯化铝法测定总黄酮含量,比较不同发酵类型茶叶的主要抗氧化成分含量的差异。采用ORAC法和DPPH·清除自由基能力法分别测定其体外抗氧化能力,并与茶叶抗氧化成分进行相关性分析,综合比较不同发酵类型茶叶体外抗氧化能力差异及其与抗氧化成分之间的相关性,比较这两种方法的准确性。试验结果表明,绿茶茶多酚【(5.221±0.707)mg/mL】及儿茶素含量【(3.520±1.025)mg/mL】显著高于乌龙茶、红茶和黑茶。随着发酵程度的加深,茶多酚及儿茶素含量明显降低。发酵过程中明显提高了红茶和黑茶中茶黄素和没食子酸的含量。由ORAC法和DPPH法测得茶叶抗氧化能力大小分别为绿茶>乌龙茶>黑茶>红茶,绿茶>乌龙茶>红茶>黑茶。由ORAC法和DPPH法测定的茶叶抗氧化能力均与茶多酚及儿茶素含量呈显著的相关性(P<0.05),表明酚类物质是茶叶抗氧化能力的主要影响因素。茶黄素明显影响乌龙茶、红茶及黑茶的抗氧化能力。两种方法的比较分析表明在检测茶叶抗氧化能力时ORAC法优于DPPH法。

ORAC（oxygen radical absorbance capacity） and DPPH （1, 1-diphenyl-2-picrylhydrazyl） assays have been received widely coverage and utilization in antioxidant and oxidative stress. But researches on antioxidant properties of g kinds of fermented teas in vitro both by ORAC and DPPH assays have not been reported. In this paper, g types of fer- mented teas （including 16 brands） from different floral origins were screened to quantify the polyphenos, catechins, theaflavins, galhc acid and total flavonoids contents, evaluate the antioxidant capacity and determine the correlations be- tween the parameters analysed. Polyphenols contents were determined by ferrous tartrate method, catechins, theafiavins and gallic acid contents using HPLC, and total flavones contents using aluminium chloride method. Teas＂ antioxidant ca- pacities were comparatively assessed by ORAC and DPPH assays. Results indicate that Green tea had significantly （P〈0.05） higher polyphenlos and catechins [（5.221＋0.707） and （3.520＋1.025） mg/mL] compared to Oolong, Black and Dark teas. With the increase of the degree of fermentation, the contents of polyphenlos and catechins reduced remark- ably. While the fermentation process significantly elevated the levels of theaflavins and gallic acid in Black and Dark teas. The antioxidant capacity as assessed by ORAC assay degreased in the order： Green tea 〉 Oolong tea 〉 Dark tea 〉 Black tea. While using the DPPH assay the following antioxidant capacity was obtained： Green tea 〉 Oolong tea 〉 Black tea 〉 Dark tea. The antioxidant capacities of teas both determined by ORAC and DPPH assays were significantly （P〈0.05） correlated with polyphenols and catechins contents, indicating that phenolic compounds are the major contributors to the antioxidant properties of teas. Furthermore, theaflavins may also be contributed to the antioxidant capacities of Oolong, Black and Dark teas. Comparative analysis shows that ORAC is superior than DPPH method to detect the antioxidant ca- pacity of tea.