Assessment of the Antioxidant, Anti-Inflammatory, and Acute Toxicity Properties of an Aqueous Extract of Origanum vulgare L

Abstract

Oregano (Origanum vulgare L., "Zaâtar") is among the plants most frequently cited in Algerian traditional medicine, where it is taken almost exclusively as an aqueous decoction. The aim of this study was to characterize chemically the aqueous decoction of Origanum vulgare aerial parts and to determine its antioxidant capacity in vitro, its acute oral toxicity and its anti-inflammatory activity in vivo. The decoction contained 388.15 ± 1.92 µg gallic acid equivalents, 104.81 ± 1.71 µg quercetin equivalents and 53.26 ± 1.71 µg catechin equivalents per mg of dry extract. It scavenged the DPPH and ABTS radicals with IC 50 values of 9.44 ± 0.33 and 6.02 ± 0.02 µg/mL, and reduced cupric and ferric ions with A 0.50 values of 9.50 ± 0.26 and 18.97 ± 0.56 µg/mL. A single oral  ose of 2000 mg/kg caused no mortality, no clinical sign and no change in body-weight gain. Given orally at 200 and 400 mg/kg, the decoction reduced carrageenan-induced paw edema at every time point (P < 0.001); repeated-measures analysis of variance showed effects of treatment (F(3,20) = 482.74), of time (F(3,60) = 111.57) and of their interaction (F(9,60) =15.43), all with P < 0.001. Mean inhibition over 4h reached 52.77 ± 0.77% at 400 mg/kg, a value indistinguishable from diclofenac (55.82 ± 2.03%; P = 0.270), whereas 200 mg/kg was less effective (48.03 ± 0.81%; P = 0.003). The traditional Algerian decoction is therefore innocuous, rich in phenolic compounds and as effective as diclofenac at 400 mg/kg.