Antioxidant Capacity of Seeds Extract of Commonly Consumed Fruits (cucumber, Tomato, Soursop, and Watermelon)

This study evaluated the in vitro antioxidant potential of seed extracts from watermelon (Citrullus lanatus), cucumber (Cucumis sativus), tomato (Solanum lycopersicum), and soursop (Annona muricata) using the DPPH radical-scavenging assay. Extracts were tested at 10, 50, and 100 µg/mL, and their percent inhibition of DPPH was recorded. All four extracts exhibited a dose-dependent increase in scavenging activity, with soursop (13.6 → 41.5 %), tomato (10.6 → 41.2 %), and watermelon (10.3 → 40.6 %) outperforming cucumber (5.1 → 29.8 %) at the highest concentration. Comparative analysis linked these differences to each seed’s phytochemical profile: watermelon and tomato seeds are rich in phenolics, flavonoids, and carotenoids; soursop seeds contain terpenoids and phytosterols; cucumber seeds, despite high oil and protein content, have fewer potent phenolics. Nutritional considerations—such as unsaturated fatty acids, proteins, and dietary fibers—further support the observed antioxidant rankings. Economically, watermelon and tomato seeds, as abundant agro-processing byproducts, offer cost-effective sources of natural antioxidants, while cucumber and soursop seeds present underexplored value-addition opportunities. These findings highlight the potential for upcycling fruit seed waste into functional ingredients for food, nutraceutical, or cosmetic applications.