Repeated oral administration of a squeezed ginger (Zingiber officinale) extract augmented the serum corticosterone level and had anti-inflammatory properties.

We investigated the ability of a ginger extract to induce an immune response in RAW 264 cells and after a repeated oral administration to mice. The squeezed ginger extract augmented the production of tumor necrosis factor-α, interleukin-6, and monocyte chemotactic protein-1 when added to RAW 264 cells. This extract was collected as its ethanol-insoluble fraction. The oral administration of the squeezed ginger extract or its ethanol-insoluble fraction once or twice to mice also augmented the tumor necrosis factor-α production in peritoneal cells; however, its long-term administration had the opposite effect. The serum corticosterone level had increased after orally administering the squeezed ginger extract and was maintained during the administration period. Oral administration of the squeezed ginger extract also inhibited arachidonic acid-induced ear edema, but its repeated administration was needed to achieve an anti-inflammatory effect. These results suggest that the repeated administration of the aqueous constituents of ginger augmented the serum corticosterone level and that this may have gradually induced anti-inflammatory activity.