<p><i>Ocimum basilicum</i> has several functional characteristics including carminative, stimulant, diuretic, antiseptic, anesthetic, anti-spasmodic, analgesic and anti-tussive properties. <i>O. basilicum</i> essential oil (basil oil) was tested for chemical composition and in vitro and ex vivo anti-oxidant activities. The in vitro anti-oxidant capacity of basil oil was examined using 1, 1-diphenyl-2-picryl-hudrazyl radical (DPPH<sup>•</sup>), 2, 2-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) radical (ABTS<sup>•</sup>), hydrogen peroxide (H<sub>2</sub>O<sub>2</sub>), hydroxyl radical (HO<sup>•</sup>), nitric oxide (NO) and nitrite (NO<sub>2</sub>) scavenging effects. The <i>ex vivo</i> anti-oxidant activity of basil oil was determined through measuring NADH oxidase (NOX) and inducible nitric oxide synthase (iNOS) mRNA expression in lipopolysaccharide-stimulated murine macrophages using real-time polymerase chain reaction (RT-PCR). GC-MS analysis indicated that the main components in the basil oil were methylchavicol (47%), geranial (19%) and neral (15%). Basil oil had effective DPPH<sup>•</sup>, ABTS<sup>•</sup>, H<sub>2</sub>O<sub>2</sub>, HO<sup>•</sup>, NO and NO<sub>2</sub> scavenging effects. Basil oil significantly reduced NOX and iNOS mRNA expression in lipopolysaccharide-stimulated murine macrophages at concentrations of 1-10 μg/mL. Basil oil had radical scavenging and anti-oxidant activities and could potentially be used as a safe and effective source of natural anti-oxidants in therapy against oxidative damage and stress associated with some inflammatory conditions.</p
