Stability Study of Epigallocatechin Gallate in a Series of Aqueous Systems
Epigallocatechin Gallate (EGCG), the major antioxidant component in Oriental Green Tea, was studied to determine its stability in a variety of systems using high performance liquid chromatography (HPLC) (Ho 1991). The systems studied were water, basic, acidic, and two acidic systems containing iron. They varied in pH, type of acid (phosphoric and citric), and the type of iron (ferrous and ferric). These systems were chosen to provide differences in the aqueous solutions that were well defined and could be used as models for beverages. The concentrations (percentages) of EGCG in solution were determined over time by HPLC, using an external EGCG standard. From the HPLC data, the rate of degradation in the various systems was determined. Of the six solutions studied, EGCG was the most stable in aqueous citric acid (pH 3.0). Adding either ferrous of ferric ions to the citric acid decreased the stability slightly. The neutral water solution was next in stability, followed by the aqueous phosphoric acid (pH 0.89), with the basic solution (pH 9.0) causing the fastest rate of degradation. All of the solutions studied had the same initial concentration of EGCG in solution.