Suppressive effects of mioga ginger and ginger constituents on reactive oxygen and nitrogen species generation, and the expression of inducible pro-inflammatory genes in macrophages

We previously conducted screening tests of the chloroform extracts from a total of 89 species of Japanese plant food items for their suppressive effects on superoxide (O₂^-) generation through both NADPH oxidase and xanthine oxidase, and reported that mioga ginger (Zingiber mioga Roscoe) indicated the strongest suppressive activities. In this study, the suppressive effects of mioga ginger constituents, aframodial, and galanal B, together with [6]-gingerol and galanolactone occurring in ginger, on free radical generation and inducible proinflammatory gene expressions were investigated. Of these constituents, aframodial (20 μM) exhibited marked suppressive effects on 12-O-tetradecanoylphorbol-13-acetate-induced O₂^- generation in HL-60 cells and lipopolysaccharide (LPS)/interferon-γ- induced nitric oxide (NO) generation in RAW264.7 cells (inhibition rates [IRs] = 84.6% and 95.9%, respectively). Aframodial also strongly suppressed the stimulated HL-60 cell-induced mutagenicity in AS52 cells (IR = 95.9%). The LPS-induced expression of inducible proinflammatory genes such as inducible NO synthase, interleukin (IL)-1β, IL-6, and granulocyte-macrophage colony-stimulating factor was significantly abolished (IRs = 99.1%, 74.6%, 74.0%, and 64.4%, respectively) by aframodial. In addition, degradation of the inhibitor of nuclear factor κB was suppressed by this compound (IR = 100%), suggesting that the suppression of nuclear factor κB activation, at least in part, is involved. Taken together, these results suggest that aframodial has potent antioxidative and anti-inflammatory potentials, and may be a promising candidate in prevention and/or therapy for chronic inflammation-associated carcinogenesis.