New metabolites of the drug 5-aminosalicylic acid. I: N-beta-D-glucopyranosyl-5-aminosalicylic acid.

1. A new unstable metabolite of 5-aminosalicylic acid (5-ASA) was found in plasma from healthy volunteers dosed with 5-ASA i.v. 2. The metabolite was prepared by incubation of 5-ASA with rat liver homogenate, and isolated using preparative h.p.l.c. 3. The metabolite was identified as N-beta-D-glucopyranosyl-5-aminosalicylic acid by n.m.r. spectroscopy and by FAB mass spectrometry. 4. N-beta-D-Glucopyranosyl-5-ASA was formed non-enzymically from 5-ASA and glucose in phosphate buffer pH 7.4, and was unstable under weakly acidic conditions, decomposition increasing with temperature, i.e. decomposition was complete after 30 min at pH 5.0 and 23 degrees C.