5-Aminosalicylic acid (5-ASA) (see PubChem for structure) is an anti-inflammatory compound that is commonly used in the treatment of inflammatory bowel disease. Mesalamine (mesalazine) is an alternative name for 5-ASA, and this ingredient occurs in several slow-release formulations such as Pentasa and Asacol. 5-ASA was first used in the treatment of IBD in the form of sulphasalazine, a compound that contains both a 5-ASA and a sulfapyridine moiety. The 5-ASA moiety was found to be the most active as an anti-inflammatory. The mode of action of 5-ASA is thought to be inhibition of nuclear factor-kappa B (NFkB) activation (Kaiser et al., 1999). This may in turn contribute to its beneficial effects in prevention of colon cancer (Cheng and Desreumaux, 2005; Eaden, 2003).