title: Investigation of the degradation mechanism of 5-aminosalicylic acid in aqueous solution.
abstract: The solution degradation of the antiinflammatory agent 5-aminosalicylic acid (5-ASA) was investigated in order to elucidate a mechanism for degradation. Two degradation pathways were considered: decarboxylation by analogy to 4-aminosalicylic acid (4-ASA) decomposition and oxidation from consideration of 5-ASA's aromatic ring substitution pattern (i.e., relation to p-aminophenol). The oxidation of 5-ASA was investigated using cyclic voltammetry and flow electrolysis. These studies showed that 5-ASA is more easily oxidized than is 4-ASA and that 5-ASA undergoes a two-electron, two-proton oxidation consistent with formation of 5-ASA-quinoneimine (5-ASA-QI). This oxidation is followed by subsequent complex chemistry. The decomposition of 5-ASA in solution was examined under a variety of conditions. 5-ASA decomposes most rapidly under conditions promoting oxidation and is most stable under conditions tending to inhibit oxidation. Decarboxylation was not found to be a significant degradation pathway.
authors.affiliation: Department of Chemistry, University of Kansas, Lawrence 66045-0049.
authors.forename: R K
authors.initials: RK
authors.lastname: Palsmeier
authors.forename: D M
authors.initials: DM
authors.lastname: Radzik
authors.forename: C E
authors.initials: CE
authors.lastname: Lunte
mesh_terms: D010131:Aminosalicylic Acid / Q000737:chemistry / Q000378:metabolism; D000636:Aminosalicylic Acids / Q000737:chemistry* / Q000378:metabolism; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000737:chemistry*; D001673:Biodegradation, Environmental; D004355:Drug Stability; D004563:Electrochemistry; D019804:Mesalamine; D010084:Oxidation-Reduction; D012996:Solutions; D014867:Water / Q000737:chemistry
chemical_list: D000636:Aminosalicylic Acids; D000894:Anti-Inflammatory Agents, Non-Steroidal; D012996:Solutions; D014867:Water; D019804:Mesalamine; D010131:Aminosalicylic Acid; C028836:N-acetyl-5-aminosalicylic acid