Protective Effect of Dioscorea batatas Peel Extract Against Intestinal Inflammation

Dioscorea batatas Decne (Chinese yam), a perennial trailing plant, has been used as a traditional medicine due to its beneficial biological effects. Recent studies reported that yam bark powder increased antioxidant enzyme activity and exerted an anti-inflammatory effect in drug-induced liver injury or colorectal cancer in rats. In this study, we examined whether ethanol extracts of yam bark (peel) could ameliorate the macrophage-induced inflammatory damage of colonic epithelial cells in culture and in an acute colitis mouse model. Human HCT116 colorectal epithelial cells and/or lipopolysaccharide (LPS)-activated murine Raw 264.7 macrophages were treated with the yam bark extract, followed by biochemical examination of cellular cytokine and antioxidant enzyme expression levels. Our results demonstrated that the yam bark extract decreased nitric oxide production and proinflammatory protein expression in LPS-activated Raw 264.7 cells, and reduced the level of reactive oxygen species in hydrogen peroxide-challenged HCT116 cells. Moreover, yam bark extract attenuated dextran sulfate sodium (DSS)-induced acute colitis in BALB/c mice. These findings suggest that oral supplementation with yam bark extract inhibited DSS-induced colon inflammation through upregulation of antioxidant enzymes and subsequent downregulation of inflammatory proteins.