Determination of Antioxidant Content and Capacity of Four Jordanian Fresh Citrus Fruits

Citrus fruits are considered one of the most grown crops worldwide including Jordan with high nutritive and non-nutritive value. The consumption of foods that contain natural antioxidants is thought to be an efficient way for reducing the risk for oxidative stress diseases. Determination of antioxidant content and capacity allows the screening of plants that are probably involved in the prevention and/or treatment of oxidative stress diseases. This study aimed at comparing four fresh Jordanian citrus fruits (namely: orange, lemon, pomelo, and mandarin) for their antioxidant content (using two methods namely: Folin-Ciocaltaeu method and total flavonoids method) and capacity (using two methods namely: 2,2-diphenyl-picrylhydrazyl (DPPH) and cupric antioxidant reducing capacity (CUPRAC) assays). Three solvents were used for the fruit extraction (ethanol, methanol, and water). There were significant (P < 0.05) differences between the fruits in terms of antioxidant content and capacity. Regardless of the extraction solvent, the fruit content of total polyphenols (M catechin/100 g) was as follows: lemon > mandarin > pomelo > orange. The total flavonoid content (mM rutin/100 g) of the fruits was: orange > mandarin > lemon > pomelo. On the other hand, the antioxidant capacity (M trolox/100 g) of the fruits was: lemon > mandarin > orange > pomelo. The antioxidant capacity (measured as mg vitamin C/ml extract) of the fruits was: mandarin > orange > pomelo > lemon. Different extracts of different fruits showed significantly (P < 0.05) different antioxidant contents and capacities. No correlation between antioxidant content and antioxidant capacity of the studied fruits has been found.