Assessment of Antioxidant Activity and Total Phenolic Content of Selected Tropical Fruit Juices in Ogun State

Oxidative stress, arising from an imbalance between free radical production and antioxidant defences, is implicated in the aetiology of numerous chronic diseases prevalent in South West Nigeria. Regular consumption of antioxidant-rich fruit juices is widely advocated as a dietary strategy for reducing oxidative damage. This study assessed the antioxidant activity and total phenolic content of freshly extracted juices from five tropical fruits commonly consumed in Ogun State, namely pineapple, guava, watermelon, pawpaw, and soursop. Juice samples were prepared and analysed using the DPPH radical scavenging assay, ABTS assay, ferric reducing antioxidant power assay, and Folin-Ciocalteu method for total phenolic determination. Ascorbic acid content was measured by the titrimetric method. Guava juice demonstrated the highest antioxidant activity across all three antioxidant assays, with an IC50 value of 3.2 micrograms per millilitre in the DPPH assay. Soursop juice ranked second in DPPH and FRAP analyses. Watermelon juice had the lowest antioxidant capacity but the highest lycopene-associated pigmentation. Total phenolic content ranged from 28.4 mg GAE/100 mL in watermelon to 187.6 mg GAE/100 mL in guava. Ascorbic acid was highest in guava at 228 mg/100 mL. Significant positive correlations were observed between total phenolic content and all three antioxidant assay values. These findings support the nutritional value of guava and soursop juices as functional beverages and provide a chemical basis for dietary recommendations promoting tropical fruit consumption for health maintenance in Ogun State.

Keywords: antioxidant activity, total phenolics, tropical fruits, DPPH assay, Ogun State