In this study, the content of cafein e (CF), theobromine (TB) and theophylline (TP) were determined in 35 tea samples, including green tea, black tea and different geographical origins (Yen Bai, Tuyen Quang, Thai Nguyen, Ha Giang, Hoa Binh and Lam Dong). High performance liquid chromatography (HPLC) method was used with the optimal separation conditions investigated. The mobile phase was a mixture of acetonitrile and 20 mM, pH = 3 phosphate buffer solution (15:85 v / v) with maximum absorption wavelength at 271 nm at room temperature. Extraction conditions was optimized by factorial design of experiments. Optimum conditions were temperature extraction of 99 ° C, extraction time of 8 minutes. The amounts of TB, TP and CF in tea had been determined by HPLC using the calibration curve. CF, with an average content of 65,8 mg g-1 was the major methylxanthine. TB and TP had average contents of 5,288
5,859 mg g-1, respectively. The coefficient of variation of the method is less than 1.0%. The recovery for CB, TP and CF ranged from 99.0% to 101.8%. The results of the 35 tea sample colected in different areas showed the weight percentages of the three substances are different. The contents of xanthines in Vietnamese tea reflectthe sources of tea from diferent areas among Northern Midland region, Northern Mountainous region and Tay Nguyen region of Vietnam. Keywords: cafein e, theobromine, theophylline
original sources
tea
HPLC