Determination of Total Antioxidant Activity of Fruit Juices Widely Consumed in Syria

Fruits are considered essential constituents of a healthy diet. They possess antioxidant properties which can be attributed mainly to their phenolic compounds. Two samples of the following fruit juices (orange, grapefruit, blackberry, black mulberry, black sweet cherry, strawberry, pomegranate, organic tomato, greenhouse tomato, black plum, black grape and red grape) were investigated for their phenolic content and total antioxidant activity. Total phenolic content was determined according to Folin-Ciocalteu method. Black mulberry juice showed the highest results with amounts from 8.6_gGAE/L_juice to 11.2_gGAE/L_juice, while the lowest was red grape juice with amounts from 0.3_gGAE/L_juice to 0.7_gGAE/L_juice. Total Antioxidant activity was subsequently determined using Ferric Reducing Antioxidant Power (FRAP) assay and reducing power assay. The results were in accordance with Folin-Ciocalteu method since black mulberry juice had the highest antioxidant power, while red grape juice had the lowest. The study indicates that black mulberry juice is the richest source of phenolic compounds and provides the highest antioxidant potential compared with other fruit juices in this study. Reducing power assay gave a similar order compared to FRAP assay. Both assays depend on reducing the ferric complex to its ferrous form which could explain the similarity in juice order considering their antioxidant activity.