Abourashed Ehab A, Roberson Cindy Leslie A, Elsharkawy Nancy
a 1 Department of Pharmaceutical Sciences, College of Pharmacy, Chicago State University , Chicago , IL , USA.
b 2 Pharmacy Practice, College of Pharmacy, Chicago State University , Chicago , IL , USA.
J Diet Suppl. 2016;13(2):171-84. doi: 10.3109/19390211.2014.965868. Epub 2014 Oct 9.
Green tea (Camellia sinensis) preparations are among the top selling products in the United States dietary supplements market. Numerous manufacturers claim different levels of specific catechin markers in their products while many others use total phenolic concentration instead, or not at all. Limited quality control results have been published for green tea dietary supplements over the past seven years. Thus, the goal of this work was to correlate determined levels of phenolics, catechins, and caffeine with manufacturer label claims for selected dietary supplement products (26 total) purchased in the United States. The Folin-Ciocalteu (FC) method was used to determine the total phenolic content while reversed-phase (RP) HPLC was used to quantify the major catechins: epicatechin (EC), epigallocatechin (EGC), epicatechin gallate (ECG), epigallocatechin gallate (EGCG). The developed HPLC method was validated for accuracy and precision. It utilized a C8 column with gradient elution of acetonitrile in 0.1% aqueous formic acid over 11 min total run time. Peak detection was performed at 280 nm. Caffeine was also included in the HPLC method as another non-phenolic alkaloid marker commonly found in green tea. Both methods showed a good correlation between the content of catechins and polyphenolic compounds in the selected products. The ranges of total catechins and polyphenol concentrations were 3.8-70.2% and 3.6-95.8%, respectively, while that of caffeine was 0.8-11.2%. The selected products displayed a wide range of marker levels. A lack of conformity in disclosing the actual levels of marker compounds was also noticed in the labeling of many products.
绿茶（茶树）制剂是美国膳食补充剂市场上最畅销的产品之一。许多制造商宣称其产品中特定儿茶素标志物的含量不同，而其他许多制造商则使用总酚浓度来表示，或者根本不提及。在过去七年中，关于绿茶膳食补充剂的质量控制结果公布得很少。因此，这项工作的目的是将选定的在美国购买的膳食补充剂产品（共26种）中测定的酚类、儿茶素和咖啡因水平与制造商标签声明进行关联。采用福林-西奥尔特（FC）法测定总酚含量，同时采用反相（RP）高效液相色谱法对主要儿茶素进行定量：表儿茶素（EC）、表没食子儿茶素（EGC）、表儿茶素没食子酸酯（ECG）、表没食子儿茶素没食子酸酯（EGCG）。所建立的高效液相色谱法经过了准确性和精密度验证。它使用C8柱，在0.1%甲酸水溶液中用乙腈进行梯度洗脱，总运行时间为11分钟。在280nm处进行峰检测。咖啡因也作为绿茶中常见的另一种非酚类生物碱标志物包含在高效液相色谱法中。两种方法都表明所选产品中儿茶素和多酚化合物的含量之间具有良好的相关性。总儿茶素和多酚浓度范围分别为3.8-70.2%和3.6-95.8%，而咖啡因的浓度范围为0.8-11.2%。所选产品显示出标志物水平的广泛差异。在许多产品的标签中还注意到在披露标志物化合物的实际水平方面缺乏一致性。
