Inflammation has been implicated in ulcerative colitis (UC) development. This study aimed to verify the effect of grape peel powder (GPP) on inflammatory response in an UC model and to identify the bioactive fraction responsible for this effect. Soluble polyphenols (PE) were extracted from GPP using methanol:H20 and acetone:H20 yielding a residue that was rich in fiber and bound phenolics (RE fraction). RE was extracted with butanol:HCl/100°C and then MeOH:H2SO4/85°C/20 h to yield a fiber-rich and phenolic poor-fraction (RF). Wistar rats were fed standard diet (SD; control) or SD supplemented with GPP (8%), PE, RE or RF fraction during 15 days before colitis induction (intracolonic 2,4,6-trinitrobenzenesulphonic acid administration) and for 7 days after induction. PE, RE, and RF doses were chosen to provide fiber and soluble and bound polyphenols at amounts equivalent to GPP group. Another group received mesalamine, a standard drug for colitis treatment. Colitis increased by 4.2-fold the colonic myeloperoxidase activity compared to control group and only RE fraction was able to decrease myeloperoxidase activity (37.6%). Serum and colonic levels of TNF-α and IL-1β also increased with colitis (1.9- and 1.7-fold; 4.7- and 2-fold, respectively). Protein expression of IKK-β and pNF-kB in colon tissue were significantly enhanced (4- and1.6-fold, respectively) (p<0.05). All diet treatments and mesalamine diminished IKK-β expression (about 50 and 59%, respectively) and colonic TNF-α levels (about 50 and 35%, respectively). GPP and RE fraction decreased pNF-kB expression (42%) and serum IL-1β levels (66 and 80%, respectively). Only mesalamine decreased (30%) colonic IL-1β levels. Serum TNF-α was diminished by GPP, RE fraction and mesalamine (42, 51, and 45%, respectively). Our results demonstrate that GPP possess great anti-inflammatory effect in UC and that fiber-associated polyphenols have greater anti-inflammatory effects than the soluble phenolics or the dietary fiber fraction of grape peel.