*2.3.2 Antioxidant activity*

Several *in vitro* studies on antioxidant activities of ginger have been investigated using (FRAP), 2,2-diphenyl-1-picrylhydrazyl (DPPH), and 2,2̕- azinobis- (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) assays [64]. Number of *in vitro* antioxidant activity assays have also been investigated by using various cell models and provided underlying mechanisms of antioxidant action [62, 64]. For example, ginger extract showed antioxidant effects in human chondrocyte cells, with oxidative stress mediated by interleukin-1*β* (IL-1*β*) [65]. It stimulated the expression of several antioxidant enzymes and reduced the generation of ROS and lipid peroxidation [62]. Additionally, ginger extract could reduce the production of ROS in human fibrosarcoma cells with H2O2-induced oxidative stress [66]. Ginger and its bioactive compounds (such as 6-shogaol) exhibited antioxidant activity via the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway [67]. 6-shogaol increased intracellular glutathione/glutathione disulfide (GSH/GSSG) and upregulated Nrf2 target gene expression in human colon cancer cells [68].
