Physicochemical characterization, antioxidant capacity, and antimicrobial activity of Citrullus colocynthis seed oil

Underutilized plant species provide sustainable sources for natural bioactive compounds. This study characterized Citrullus colocynthis seed oil (CCSO) from Adama, Ethiopia, extracted via an optimized Soxhlet protocol using ethanol (1:10 w/v, 60°C, 6 h). Physicochemical analysis confirmed that the oil meets FAO/WHO Codex standards for unrefined oils, featuring an acid value of 4 ± 0.51 mg KOH/g and a peroxide value of 7.44 ± 0.46 meq O₂/kg, indicating high oxidative stability. GC-MS analysis identified linoleic acid (45.90%) and oleic acid (23.05%) as the primary fatty acids. Ethanol extracts demonstrated significant dose-dependent antioxidant capacity (90.95% DPPH scavenging at 12 mg/mL; FRAP of 4.79 ± 0.01 mmol Fe/g), which strongly correlated with high phenolic (225.64 ± 1.06 mg GAE/g) and flavonoid (126.87 ± 1.14 mg CAE/g) content (r = 0.95-0.98, p < 0.05). Furthermore, antimicrobial assays revealed concentration-dependent activity, particularly against S. aureus (22 mm inhibition zone), with stronger efficacy against Gram-positive than Gram-negative strains. These findings highlight CCSO's potential as a functional bioresource for food and pharmaceutical applications; however, further in vivo studies are required to validate its safety and industrial feasibility.