Enzymatic conjugation and hydrolysis of [18O]isoborneol glucuronide.

Introduction of 18O into the acetal linkage of isoborneol glucuronide has been accomplished through the in vitro enzymatic conjugation of 18O-labeled isoborneol by use of immobilized, partially purified, rabbit liver UDP-glucuronyltransferase supplemented with UDP-glucuronic acid. Mass-spectrometric analysis of 18O enrichment in both the aglycon and the intact conjugate made it possible to study both enzymatic conjugation and enzymatic hydrolysis. Analysis by gas chromatography-mass spectrometry indicated that the labeled hydroxyl oxygen of isoborneol is retained during both conjugation and hydrolysis.