Abstract
The solution degradation of the antiinflammatory agent 5-aminosal-icylic acid (5-ASA) was investigated in order to elucidate a mechanism for degradation. Two degradation pathways were considered: decarboxylation by analogy to 4-aminosalicyclic 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.
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Palsmeier, R.K., Radzik, D.M. & Lunte, C.E. Investigation of the Degradation Mechanism of 5-Aminosalicylic Acid in Aqueous Solution. Pharm Res 9, 933–938 (1992). https://doi.org/10.1023/A:1015813302412
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DOI: https://doi.org/10.1023/A:1015813302412