A study of the stability of antioxidant activity of green tea extract powder with vitamin C

Background: Green tea contains Epigallocatechin gallate (EGCG), the highest antioxidant activity. EGCG is an unstable compound due to degradation. Vitamin C is thought to be able to regenerate EGCG radicals into normal forms and increase green tea's antioxidant activity. Objective: The aim of this research was to determine the effect of adding vitamin C in maintaining the stability of the antioxidant activity of green tea. Method: This research was carried out by using UV-Vis spectrophotometry to determine the rate of decreasing antioxidant activity at 0 hours, six hours, and 24 hours by the 2,2-diphenyl-1-picrylhydrazyl (DPPH) method. Result: IC₅₀ values of green tea before and after the addition of vitamin C were obtained at 147.53 ppm and 97.75 ppm, respectively. The degradation rate of green tea before and after the addition of vitamin C was 0.4228 %/hour and 0.3231 %/hour, respectively. Conclusion: The antioxidant activity of green tea with vitamin C is greater than without vitamin C addition. The degradation rate of green tea with vitamin C is smaller than green tea only, so the authors suggest the addition of vitamin C to green tea extract powder products to increase the stability of its antioxidant activity.