HIGH-PERFORMANCE LIQUID-CHROMATOGRAPHIC QUANTIFICATION OF 4-METHYLUMBELLIFERYL-BETA-D-GLUCURONIDE AS A PROBE FOR HUMAN BETA-GLUCURONIDASE ACTIVITY IN TISSUE-HOMOGENATES

An internally standardized HPLC method to determine the concentration of 4-methylumbelliferone liberated from 4-methylumbelliferyl-beta-D-gl ucuronide by human beta-glucuronidase was developed. The assay allows the precise and rapid measurement of specific enzyme activity in human tissue homogenates. Without prior extraction the incubation mixture c an be separated using a C-8 column followed by fluorescence detection. The assay showed good accuracy and precision with a detection limit o f 20 nM and a limit of quantification of 167 nM. The suitability of th e method was shown in enzyme kinetic experiments with human liver homo genates.