Anti-inflammatory and analgesic effects of an aqueous extract of Harpagophytum procumbens.

The dried aqueous extract of Harpagophytum procumbens (Pedaliaceae) and its main iridoid glycoside, harpagoside, have been evaluated for anti-inflammatory and analgesic effects in mice and rats, in order to validate or invalidate the involvement of this compound in such properties. This extract exerted significant and dose-dependent anti-inflammatory and analgesic effects, from the dose 100 mg of dried secondary roots/kg, the first being obtained on an acute inflammatory process (carrageenan-induced edema test in rats) and the second being obtained against a chemical stimulus (writhing test in mice). Harpagoside does not appear to be involved in anti-inflammatory properties, since this iridoid glycoside did not protect against carrageenan inflammatory effects when it was used at 5 and 10 mg/kg; 5 mg corresponding to the quantity contained in 400 mg of dried secondary roots. The main iridoid glycoside of H. procumbens appears to be implicated in the peripheral analgesic properties of this species, but other compounds have to be involved, since the dose of 10 mg/kg exerted a significant protective effect. The absence of the activity of H. procumbens after an acid treatment (0.1 N hydrochloric acid), stomach, suggests the use of a suitable galenic preparation in order to protect the active principles from the action of the acid released in the stomach.