In vivo anti-inflammatory activity of the essential oil of zingiber officinale rhizomes on Wistar rats

Background: Zingiber officinale is a spice consumed in Chad and traditionally used against osteoarthritis, migraine and rheumatic pain, but few pharmacological studies of this plant have been carried out. The aim of this study was to assess the in vivo anti-inflammatory activity of Z. officinale rhizomes essential oil (EO).

Methods: A preliminary phytochemical screening was carried out on the EO of Z. officinale rhizomes; the anti-inflammatory activity of the given plant extract was then assessed at the concentrations of 0.20%, 1% and 5% on three experimental models: egg yolk-induced oedema, cotton pellet-induced granuloma and formalin. In addition, the essential oil was tested for its in vitro antioxidant capacity using the 2,2-Diphényl-2-picryl-hydrazyle Free Radical Scavenging Test, acide 2,2'-azino-bis 3éthylbenz- thiazoline-6-sulfonique Radical Test and the Ferric reducing antioxidant power Test. The study was extended to the acute toxicity of the EO of the rhizomes of Z. officinale using the sequential method. 

Results: Qualitative phytochemical screening of the EO of Z. officinale rhizome revealed the presence of tannins, flavonoids, triterpenes, terpenoids and free quinones. In the egg yolk-induced edema model, the EO of Z .officinale rhizomes significantly inhibited (p < 0.01) oedema by 25.28%, 31.12% and 68.27% at the concentrations of 0.20%, 1% and 5%, respectively, when compared to controls.  In the formalin-induced paw edema model, EO of Z. officinale rhizomes inhibited oedema by 24.27%, 30.14% and 43.14% at the concentrations of 0.20%, 1% and 5%, respectively, when compared to the controls. In the cotton pellet-induced granuloma model, EO of Z. officinale rhizomes induced an anti-granulomatous effect of 32.68%, 38.27% and 41.51% at the concentrations of 0.20%, 1% and 5%, respectively, as compared to controls. Additionally, the EO of the rhizomes of Z. officinale also induced in vitro antioxidant and free radical scavenging activity and iron reduction. Definitely, the LD50 of the EO of Z. officinale    rhizomes was estimated as more than 2000 mg/kg b.w.

Conclusion: The EO of Z. officinale rhizomes exhibited anti-inflammatory activity. This effect can be explained, at least partly to its chemical content and its antioxidant potential.