Antioxidative and anti-hydrogen peroxide activities of various herbal teas

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 H2O2 in the teas were also examined, since the production of H2O2 in beverages such as coffee and green tea, has been reported. Only a small amount of H2O2 was detected in the herbal teas just after their preparation with hot water. However, H2O2 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-H2O2 activity of herbal teas, various teas were added to a catechin-enriched green tea, which produce much H2O2, and they were incubated at 25 °C for one day. Addition of hibiscus and thorn apple tea decreased the production of H2O2 in the catechin-enriched green tea, possibly because of a lowering of the pH of the mixture.