Levels of total polyphenol, flavonoid, tannin and antioxidant activity of selected Ethiopian fermented traditional beverages

Indigenous fermented beverages are very popular traditional drinks in Ethiopia. Among these, korefe, tej and tella are very common in northern part of Ethiopia. However, there is no any report on the total polyphenol, flavonoid, tannin and antioxidant activity of these beverages. The purposes of this study were to determine total phenolic, flavonoids, tannins, and their antioxidant activity and to compare these parameters of selected Ethiopian traditional alcoholic beverages (korefe, tej and tella) from different origins of Ethiopia within the same sample type and between different sample types. For these purposes, methanolic extracts (70%) were prepared for semi-solid samples. Total phenolic content was determined by Folin-Ciocalteu’s method, total flavonoids content was determined by aluminium chloride (AlCl³ ) method, total tannin content was determined by indirect method precipitating protein with gelatin, while 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity method was used to determine the total antioxidant activity. The total phenolic content obtained as gallic acid equivalent, GAE mg L-¹was: korefe (285–326), tej (369–390) and tella (435–459); the total flavonoids content obtained as catechin equivalent, CE mg L-¹ was: korefe (190–199), tej (183– 190) and tella (211–216); the total tannin content obtained as tannic acid equivalent, TAE mg L-¹ was: korefe (19.9–25.9), tej (17.9–19.4) and tella (28.8–30.8) and the total antioxidant activity obtained as ascorbic acid equivalent, AAE mgL-¹ was: korefe (479–498), tej (465–479) and tella (541–561). Statistically at 95% confidence level one way ANOVA displayed that the levels of total polyphenol, flavonoid, tannin and antioxidant activity were significantly different between korefe, tej and tella. For all the determined parameters, tella exhibited a highest value. Pearson correlation showed there were positive correlations between phenolic, flavonoids and tannin with antioxidant activity assayed (r = 0.969, r = 0.931 and r = 0.944, respectively).