Development and validation potentiometric method for determination of antioxidant activity of epigallocatechin-3-O-gallate

There is high interest of scientists in the study of antioxidant activity (AOA) of different objects, which is caused by study influence of free radicals on developing pathological process in human’s body. Today, there is no main method that would be used to assess antioxidant activity. In our view, the development and modification of existing methods for determining antioxidant activity is a topical and prospective task of the pharmacy, cosmetic and food industries. The aim of study was to develop and validate potentiometric method for determination of antioxidant activity of epigallocatechin-3-O-gallate (EGCG). The object of the study was EGCG. Potentiometric measurements were conducted by pH meter Hanna 2550 (Germany) with a combined platinum electrode EZDO 5010. For assessing the level of AOA of EGCG was chosen following optimal conditions: K3[Fe(CN)6] was used as oxidizer, an electrode was made of platinum material, a 0.067 mol/L phosphate buffer solution with pH 7.2 – 7.4 was chosen as electrolyte, the ratio of K3[Fe(CN)6] /K4[Fe(CN)6] equaled 0.002/0.00002 mol/L. The linearity was in the concentration range of 0.002 – 0.02 mol/L (r2 = 0.9992). The percentage of recovery was found to be in the range from 96.01 to 101.61 %. The values of %RSD for repeatability and intermediate precision were 1.86 and 1.34 %. The potentiometric method for determination of antioxidant activity of EGCG was developed and validated according by the following parameters: linearity, accuracy, repeatability, intermediate precision. It was proved that the developed method is express, rapid, highly sensitive, accurate and sufficiently precise.