Isocratic elution system for the determination of catechins, caffeine and gallic acid in green tea using HPLC

doi:10.1016/S0308-8146(99)00179-X

Food Chemistry

Volume 68, Issue 1, January 2000, Pages 115-121

https://doi.org/10.1016/S0308-8146(99)00179-X Get rights and content

Abstract

A simple high performance liquid chromatographic analysis for tea catechins, caffeine and gallic acid with an isocratic elution system was developed. The separation system consisted of a C18 reversed-phase column, an isocratic elution system of methanol/water/orthophosphoric acid, and an UV detector. This method is ideally suited for rapid, routine analysis for the determination of catechins in green tea with good repeatability and accuracy of results. Furthermore, this method can be applied to all kinds of tea and tea products, and is especially useful for the determination of (+)-catechin, which was regarded as being in too low a concentration to detect, and (−)-gallocatechin gallate, which was regarded as a measure for heat treatment for green tea.

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.

Section snippets

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.

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Analytical, Nutritional and Clinical Methods SectionIsocratic elution system for the determination of catechins, caffeine and gallic acid in green tea using HPLC

Abstract

Introduction

Section snippets

Samples

Selection of mobile phases

Conclusions

Acknowledgements

Journal of Chromatography A

Journal of Chromatography A

Journal of Chromatography A

Cancer Letters

Journal of Chromatography

Food Chemistry

Method for determining the content of catechins in tea infusions by high-performance liquid chromatography

Journal of Chromatography A

Analytical, Nutritional and Clinical Methods Section
Isocratic elution system for the determination of catechins, caffeine and gallic acid in green tea using HPLC