EVALUATION OF ANTIOXIDANT ACTIVITY OF SOME COMMERCIAL BRANDS OF GREEN AND BLACK TEA IN UYO METROPOLIS OF AKWA IBOM STATE, NIGERIA

Uwemedimo Francis Umoh*, Emmanuel Iweh Etim, Imo Essiet Jacobs, Danladi Ngyan Bala and John Akpan Udobang

ABSTRACT

This research work was to evaluate some available commercial brands of green and black tea in Uyo metropolis in Akwa Ibom State of Nigeria to authenticate their quality at the point of consumption. Five (5) brands of green tea coded G1-G5 and three brands of black tea coded (B1-B3) were purchased randomly from some supermarkets in Uyo metropolis. Twenty five (25 g) of each of the tea brands were weighed, macerated with aqueous ethanol (70%). The filtrates were collected, concentrated and stored in the refrigerator. The antioxidant evaluation was carried out through the assessment of the tea packets, DPPH scavenging assay, iron chelating assay, estimation of total phenolic and total flavonoid contents. Result revealed that some of the teas were not properly labeled and for DPPH scavenging activity, B2 had a value of 82.4% at 100 μg/mL thereby demonstrating the highest scavenging activity for the black teas while G3 with 84.9% at 100 μg/mL demonstrated highest scavenging effect for the green teas. For iron chelating assay, B3 demonstrated the highest activity at all concentrations (20 μg/mL- 100 μg/mL) while G1 and G3 were highest for the green teas. In total phenol estimation assay, B1 showed the highest phenolic content for black teas while G4 was highest for green teas. Total flavonoid estimation revealed B1as having the highest flavonoid contents for black teas and G4 for the green teas. The results from this study authenticate the quality of these teas and confirm their suitability for consumption.

Keywords: Antioxidants, evaluation, teas and quality.