ANTIOXIDANT ACTIVITY AND IMMUNOMODULATORY EFFECT OF BLACK TEA INCORPORATED WITH RED GRAPE POMACE EXTRACT SWEETENED BY STEVIOSIDE

Abstract

Red grape pomace extract (RGPE) was chromatographically analyzed for its individual phenolic and flavonoid compounds. This extract was also characterized regarding its total phenolic content (TPC), total flavonoid content (TFC) and antioxidant activities in terms of scavenging DPPH free radicals. The TPC of RGPE was 31.37 mg of gallic acid equivalents (GAE)/g of extract, and TFC was 3.76 mg of quercetin equivalents/g of extract. Some phenolic compounds including ellagic acid, pyrogallol, catechin, benzoic and cinnamic were identified. Also, identification of TFC appeared high amount of rutin and quercitrin. Tea infusions from black tea incorporated with RGPE and sweetened with stevioside were investigated. The antioxidant activities DPPH scavenging capacity and total phenolics were determined in water extracts of formulated tea infusions, stevioside and black tea. Also, in this study, Phagocytosis inhibition test was carried out to measure immunomodulatory activity of RGP extract, stevioside, black tea and formulated tea infusion. Immunological tests showed that the treatments significantly increased phagocytosis of macrophages. Depending on sensory evaluation, the formulated tea infusion showed overall acceptance compared to normal tea. So, it could be conclude the suitability of red grape pomace extract and stevioside are suited as a supplementation in the production of health promoting beverage.