Analytical, Nutritional and Clinical Methods SectionIsocratic elution system for the determination of catechins, caffeine and gallic acid in green tea using HPLC
Introduction
It has been discovered that green tea contains various components with anti-oxidative and anticarcinogenic properties (Dreosti et al., 1997, Jankun et al., 1997, Yang, 1997). Of these, catechins, which make up about 20% of the dry weight of green tea, are thought to be the most important.
Green tea catechins are structurally primarily flavanols. The main catechins in green tea are (−)-epigallocatechin gallate (EGCG), (−)-epigallocatechin (EGC), (−)-epicatechin gallate (ECG), and (−)-epicatechin (EC).
In recent years, there have been more and more applications for tea extracts, especially in the pharmaceutical and food areas. Increased demand for tea extracts has resulted in the recognition of the inherent value of routine quality control methods to determine the catechins in both the extracts and the crude plant materials. High performance liquid chromatography (HPLC) is normally used as the analytical technique to determine catechins in green tea (Bronneer & Beecher, 1998, Dalluge et al., 1998, Goto et al., 1996, Price & Spitzer, 1993, Suematsu et al., 1995, Wang et al., 1998). In these systems complex mobile phases are needed. The use of HPLC/MS (Lin, Ng & Tang, 1993) and capillary electrophoresis (Horie, Mukai & Kohata, 1997) have been reported. However, as highly precise instruments were involved, their utilisation for routine analysis is limited. Recently, a study of stationary phases and elution conditions for the HPLC determination of six catechins has been reported by Dalluge et al. However, their initial efforts to develop an isocratic elution system for the separation of catechins were unsuccessful.
This paper presents an isocratic elution system for the separation of catechins in green tea. The system employs a simple mobile phase containing methanol and water. In addition, gallic acid and caffeine can be separated simultaneously by this method.
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Samples
Roasted green tea and Keemun black tea were obtained from the Tea Research Institute, Chinese Academy of Agricultural Sciences. Gunpowder tea and Ceylon black tea were purchased from a local teashop in Hitchin, Hertfordshire, UK. Sencha tea was a present from Japan. The tea samples were prepared according to the conventional tea brewing method, taking 3 g of sample and infusing with 150 ml of boiling distilled water for 5 min. The infusions were then filtered and kept at room temperature, and
Selection of mobile phases
Two mobile phases, one containing methanol and the other containing acetonitrile, were tested. The methanol/water system gave a complete separation of the seven catechins, caffeine, and gallic acid. However, although reasonable separation was achieved with the acetonitrile/water system, (−)-EGC and (+)-C could not be separated.
It was reported that the presence of acid in the mobile phase is essential for the complete separation and elution of the analytes (Dalluge et al., 1998). Fig. 1 shows
Conclusions
The isocratic method developed for the determination of catechins in green tea is ideally suited for rapid, routine analysis. With this method good repeatability of the results was established, and seven different catechins, caffeine, and gallic acid could be determined at the same time. Furthermore, this method is simple, sensitive and accurate and can be applied to all kinds of tea and tea products.
Acknowledgements
The authors would like to thank Mr. Clive Welham, Miss Joanne Dobbs and Mrs. Kay Skingsley for their help in the work.
References (14)
- et al.
Selection of column and gradient elution system for the separation of catechins in green tea using high-performance liquid chromatography
Journal of Chromatography A
(1998) - et al.
Simultaneous analysis of individual catechins and caffeine in green tea
Journal of Chromatography A
(1996) - et al.
Simultaneous determination of qualitatively important components in green tea infusions using capillary electrophoresis
Journal of Chromatography A
(1997) - et al.
A RP-HPLC method for the determination of tea catechins
Cancer Letters
(1997) - et al.
Characterization of flavonoids by liquid-chromatography tandem mass-spectrometry
Journal of Chromatography
(1993) - et al.
Variations in the amounts of individual flavanols in a range of green teas
Food Chemistry
(1993) - et al.
Method for determining the content of catechins in tea infusions by high-performance liquid chromatography
Journal of Chromatography A
(1998)
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