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

Aim:
This study assesses the antioxidant potential of ethanolic (EE) and water extracts (WE) from four Omani plant species, including Ocimum basilicum, Teucrium polium, Cleome amblyocarpa, and Caralluma Arabica.

Methods:
Antioxidant activity was evaluated using five assays: 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 Ocimum basilicum EE showing the highest activity (IC50 = 0.25 ± 0.022 mg/mL). Ocimum basilicum EE also displayed also the strongest NO scavenging (IC50 = 0.02 ± 0.002 mg/mL), surpassing ascorbic acid. In the FRAP assay, WE demonstrated superior reducing power (p = 0.01), with Cleome amblyocarpa WE exhibiting the highest activity (7.42 ± 0.015 mg/mL). TEAC and TAC assays revealed species- and solvent-dependent variations, with EE generally showing greater antioxidant activity, except for Cleome amblyocarpa WE, which had a significantly higher TAC (p < 0.001). Two-way ANOVA identified plant species as the primary determinant of antioxidant potential (p < 0.0001).

Conclusion:
These findings underscore the strong antioxidant properties of selected Omani plants, particularly Ocimum basilicum and Caralluma arabica, highlighting their potential for therapeutic and nutraceutical applications.

Key words: Antioxidant activity; DPPH free radical scavenging; Ethanolic extract; Oman; Water extract.