Isolation and characterization of a new human urinary metabolite of diclofenac applying LC-NMR-MS and high-resolution mass analyses.

The nonsteroidal anti-inflammatory drug diclofenac is widely used. Diclofenac is extensively metabolized to several hydroxylated derivatives and their conjugates. The lactam-dehydrate of 4'-hydroxy diclofenac (4'-OHDD) has now been detected as a new urinary metabolite of diclofenac. Isolation was successfully performed using preparative HPLC in three different steps using water, methanol, and acetonitrile, respectively. The structural characterization of 4'-OHDD was achieved by LC-NMR-MS. In addition, specific mass fragmentation pattern could be obtained using LC-high-resolution MS with both positive and negative electrospray ionization.