Comparative antioxidant activity of four Omani medicinal plants: Ocimum basilicum, Teucrium polium, Caralluma arabica, and Cleome amblyocarpa.

Background: Recent studies have linked various types of cancer to free radicals, driving research into plant-derived compounds that may mitigate oxidative damage.

Aim: To evaluate the antioxidant potential of ethanolic (EE) and water extracts (WEs) from four Omani plant species: Ocimum basilicum, Teucrium polium, Cleome amblyocarpa, and Caralluma arabica.

Methods: Antioxidant activity was assessed using the following five assays: 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical-scavenging, nitric oxide (NO) radical scavenging, ferric reducing antioxidant power (FRAP), Trolox equivalent antioxidant capacity (TEAC), and total antioxidant capacity (TAC). Ascorbic acid and Trolox were used as reference antioxidants.

Results: Both extracts exhibited dose-dependent DPPH scavenging, with O. basilicum EE showing the highest activity (IC₅₀ = 0.25 ± 0.022 mg/ml). Ocimum basilicum EE also displayed the strongest NO scavenging activity (IC₅₀ = 0.02 ± 0.002 mg/ml), surpassing that of ascorbic acid. WE demonstrated superior reducing power (p = 0.01) in the FRAP assay, with C. amblyocarpa WE exhibiting the highest activity (7.42 ± 0.015 mg/ml). TEAC and TAC assays revealed species- and solvent-dependent differences, with EE generally showing greater antioxidant activity, except for C. amblyocarpa WE, which exhibited a significantly higher TAC (p < 0.001). Two-way ANOVA identified plant species as the primary determinant of antioxidant potential (p < 0.0001).

Conclusion: The strong antioxidant properties of selected Omani plants, particularly O. basilicum and C. arabica, highlight their potential for therapeutic and nutraceutical applications.