**4.1 Animal models of IBD**

In IBD oxidative stress mediates disease progression by disrupting epithelial cell integrity. Acetic acid-induced colitis is helpful to screen herbs which can inhibit cytotoxic effects of reactive oxygen species (ROS). Dextran sulphate sodium (DSS)-induced colitis is also a frequently used animal colitis model in ethnopharmacological studies. This model is useful to test the effect of herbs on inflammatory cytokines mediated cellular injury (Dieleman et al., 1998). The transgenic rat model (HLA-B27) with overt chronic gastrointestinal tract inflammation also serves to screen medicinal herbs to treat IBD.


also suppressed colonic MPO accumulation and pro-inflammatory mediators (TNFα, IL-1, IL-6 and nitric oxide) (Cho et al., 2011).

