ocimum basilicum has several functional characteristics including carminative, stimulant, diuretic, antiseptic, anesthetic, anti-spasmodic, analgesic and anti-tussive properties. o. basilicum 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 (dppho), 2, 2-azino-bis (3-ethylbenzthiazoline-6-sulfonic acid) radical (abtso), hydrogen peroxide (h2o2), hydroxyl radical (hoo), nitric oxide (no) and nitrite (no2) scavenging effects. the ex vivo 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 dppho, abtso, h2o2, hoo, no and no2 scavenging effects. basil oil significantly reduced nox and inos mrna expression in lipopolysaccharide-stimulated murine macrophages at concentrations of 1-10 g/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.