Antioxidative and anti-hydrogen peroxide activities of various herbal teas

Abstract

Herbal teas, i.e., extracts of herbs, are popular because of their fragrance and antioxidative activity. Since the antioxidative activity comes mainly from polyphenols, total polyphenol concentrations and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging activities in herbal teas were measured and compared. Levels of H 2O 2 in the teas were also examined, since the production of H 2O 2 in beverages such as coffee and green tea, has been reported. Only a small amount of H 2O 2 was detected in the herbal teas just after their preparation with hot water. However, H 2O 2 was gradually produced during incubation at 25 °C after extraction with hot water, especially when the teas were incubated in phosphate buffer at pH 7.4. To examine the anti-H 2O 2 activity of herbal teas, various teas were added to a catechin-enriched green tea, which produce much H 2O 2, and they were incubated at 25 °C for one day. Addition of hibiscus and thorn apple tea decreased the production of H 2O 2 in the catechin-enriched green tea, possibly because of a lowering of the pH of the mixture.