ABSTRACT. The present work was aimed to determine the contents of ascorbic acid and the antioxidant activity of eight types of common fruits commercially available in Addis Ababa, Ethiopia using iodometric titration and UV-Vis spectrophotometric methods, respectively. The contents of ascorbic acid were found in the range 15.41 mg/100 g in grapes to 78.01 mg/100 g in papaya. The antioxidant activity was found highest in papaya (89.41) and lowest in water melon (31.28) in mg of ascorbic acid equivalent per 100 g of the edible part of fruit juice. The calibration curve of ascorbic acid was in the range 50 - 3.125 mg/L with R2 = 0.9994. The results also revealed the strong correlation (r = 0.863) between ascorbic acid contents in fruits and their antioxidant activity. Using the optimized conditions, UV-Vis spectrophotometric method with the 2,2-diphenyl-1-picrylhydrazil assay allows determination of antioxidant activity of fruits with limit of detection 0.32 mg/L and limit of quantification 0.96 mg/L. The precision was in the acceptable range (relative standard deviation, RSD < 20%) for determination of ascorbic acid and < 10% for antioxidant activity determination. The recovery of ascorbic acid was between 85% and 113% for selected fruits showing good accuracy of the results.   KEY WORDS: Fruits, Ascorbic acid contents, Antioxidant activity, Free radical scavengers, Iodometric titration, UV-Vis spectrophotometry   Bull. Chem. Soc. Ethiop. 2023, 37(2), 277-288.                                                            DOI: https://dx.doi.org/10.4314/bcse.v37i2.3

Teff [Eragrostis tef (Zuccagni) Trotter] is a cereal grain originating in Ethiopia as a staple food for millions of people. Its grain is a gluten-free superfood and got acceptance as a medicinal ingredient. Therefore, it is worthwhile to determine the antioxidative activities and L-ascorbic acid contents of teff grain and its baked food (injera). This study aimed to determine the ascorbic acid contents and antioxidant activities in the aqueous extract of the white and brown teff grains and their injera samples using iodimetric titration and UV-Vis spectrophotometric methods, respectively. The ascorbic acid contents in the white and brown teff ranged from 67.9–112.6 mg/100 g and 69.2–117.2 mg/100 g, respectively, and those in injera of the selected teff samples ranged from 30.5–32.9 mg/100 g and 37.3–43.0 mg/100 g, respectively. The antioxidant activities ranged from 1.26–7.04 μmol AAE/g for the white teff grains, 1.44–6.29 μmol AAE/g for the brown teff grains, 1.81–2.47 μmol AAE/g for white teff injera, and 3.89–4.86 μmol AAE/g for the brown teff injera samples. Findings of the present study have revealed that white teff and brown teff grains and their injera were found to have a higher content of ascorbic acid than commonly consumed grains and vegetables. No significant difference (α = 0.05) has been observed between the two varieties of teff grains with respect to the ascorbic acid content and antioxidant activities. However, there was a statistically significant difference (α = 0.05) in the ascorbic acid content and antioxidant activities between the teff grains and their injera samples. Therefore, this study indicated that teff grains and injera are rich in ascorbic acid content and antioxidant activities as compared to other cereal grains and are very crucial for human nutrition and health.