Studies in detoxication. 67. The biosynthesis of the glucuronides of umbelliferone and 4-methylumbelliferone and their use in fluorimetric determination of beta-glucuronidase.

Umbelliferone (7-hydroxycoumarin) and its conjugates appear to be metabolites ofcoumarin in the rabbit (Mead, Smith & Williams, 1955). It was observed that, although umbelliferone fluoresced strongly in ultraviolet light at pH 9-10, its conjugates showed little or no fluorescence. The glucuronide and ethereal sulphate of umbelliferone were therefore made and the former was found to be practically non-fluorescent. The possibility that these conjugates could be used as substrates for the determination of ,-glucuronidase and arylsulphatase was therefore investigated. Since umbelliferone is highly fluorescent it appeared likely that these conjugates could be used for the deternination of the enzymes in very small amounts of material. The present communication deals with the use of the glucuronides of umbelliferone and the cheaper 4-methylumbelliferone (7-hydroxy-4methylcoumarin) for the determination of f,glucuronidase. (This work has been briefly reported by Mead, Smith & Williams, 1954.) The ethereal sulphates of -umbelliferone and 4-methylumbelliferone show a fluorescence which is considerably less than the corresponding hydroxycoumarins. We have attempted to use these compounds for the fluorimetric assay of arylsulphatase, but we do not consider them satisfactory because their fluorescence is sufficient to give relatively high blank values. The ,B-glucosides of umbelliferone and 4methylumbelliferone, however, have been found to be satisfactory for the determination of ,-glucosidase, and an account of these compounds will be given later.