Cheng Qian, Cai Shengbao, Ni Dejiang, Wang Ruojun, Zhou Feng, Ji Baoping, Chen Yuqiong
College of Food Science & Nutritional Engineering, China Agricultural University, No.17 Tsinghua East Road, Haidian District, Beijing, 100083 China.
College of Horticulture and Forestry Science, Huazhong Agricultural University, No.1, Shizishan Street, Hongshan District, Wuhan, Hubei Province 430070 China.
J Food Sci Technol. 2015 Feb;52(2):928-35. doi: 10.1007/s13197-013-1059-y. Epub 2013 Jun 18.
In the present work, Qingzhuan tea, a unique dark tea produced by post-fermentation technology, was selected to investigate its antioxidant and pancreatic α-amylase inhibiting activities. Water extract of Qingzhuan tea was successively isolated by solvent partitioning procedures to obtain chloroform, ethyl acetate, n-butanol, sediment and residual aqua fractions. Of different fractions, the ethyl acetate fraction (QEF) had the highest total polyphenols and catechins contents, demonstrated the strongest DPPH radical scavenging activity and exhibited the greatest inhibitory effect on porcine pancreatic α-amylase activity in vitro. Further separation of QEF by a Sephadex LH-20 column generated eight subfractions (QEF1-QEF8), with QEF8 being the most active subfraction based on the assays above mentioned. The major active components in QEF8 were identified as catechins EGCG and ECG by LC-MS analysis, with contents of 22.29 % and 11.11 % respectively. Inhibitory effects of catechin standards EGCG and ECG on porcine pancreatic α-amylase activity were also observed. In conclusion, Qingzhuan tea or its water extract could be potentially used as complementary therapy ingredients for diabetes treatment through lowering postprandial blood glucose, and catechins EGCG and ECG may be the most efficient components in the water extract.
在本研究中，选取了采用后发酵工艺生产的独特黑茶——青砖茶，来研究其抗氧化和抑制胰腺α-淀粉酶的活性。通过溶剂分配程序对青砖茶水提取物进行连续分离，得到氯仿、乙酸乙酯、正丁醇、沉淀物和残留水相部分。在不同部分中，乙酸乙酯部分（QEF）的总多酚和儿茶素含量最高，表现出最强的DPPH自由基清除活性，并且在体外对猪胰腺α-淀粉酶活性具有最大的抑制作用。通过葡聚糖凝胶LH-20柱对QEF进行进一步分离，得到八个亚部分（QEF1-QEF8），基于上述测定，QEF8是活性最高的亚部分。通过液相色谱-质谱分析确定QEF8中的主要活性成分是儿茶素表没食子儿茶素没食子酸酯（EGCG）和表儿茶素没食子酸酯（ECG），含量分别为22.29%和11.11%。还观察到儿茶素标准品EGCG和ECG对猪胰腺α-淀粉酶活性的抑制作用。总之，青砖茶或其水提取物可能通过降低餐后血糖，潜在地用作糖尿病治疗的辅助治疗成分，并且儿茶素EGCG和ECG可能是水提取物中最有效的成分。
