Glucuronuria in the koala
STUART MCLEAN,1,∗ SUE BRANDON,1 NOEL W. DAVIES,2 REBECCA BOYLE,1 WILLIAM J. FOLEY,3 BEN MOORE,3 and GEORGIA J. PASS1,4
1School of Pharmacy University of Tasmania Tasmania 7000, Australia
2Central Science Laboratory University of Tasmania Tasmania 7000, Australia
3Division of Botany and Zoology Australian National University ACT 0200, Australia
4Current address: Merck Sharp & Dohme The Neuroscience Research Centre
Glucuronuria is normal in marsupial folivores such as the koala (Phascolarctos cinereus), which excretes 2–3 g glucuronic acid daily. Although this has long been attributed to the metabolites of Eucalyptus terpenes, we have found that these are mostly excreted in the unconjugated form. We now report on the aglycones that account for most of the glucuronic acid in koala urine. Urine (24 hr) was collected from six male koalas (8.8±0.4 kg, mean±SE) that were maintained on E. cephalocarpa foliage. Urine samples were analyzed by liquid and gas chromatography (LC and GC) coupled with mass spectrometry (MS). Glucuronides were readily identiﬁed by LC-MS/MS, which generated characteristic product ions at m/z 113 and 175. From the corresponding parent glucuronide ions, the masses of the aglycones were calculated. Conﬁrmation of identity was by GC-MS after hydrolysis with β-glucuronidase and comparison with standard compounds. Quantitation was by GC. The major non-terpeneaglycones were 4-methylcatechol, resorcinol, salicyl alcohol, and two unidentiﬁed C7H8O2 phenols. Smaller amounts of benzoic acid, benzyl alcohol, orcinol, pcresol, phenol, and phloroglucinol were detected. We have previously reported that terpene metabolites account for about 10% urinary glucuronides in the same koalas fed E. cephalocarpa. The present study found that an additional 60% urinary glucuronic acid is conjugated with non-terpene, mainly phenolic, aglycones. It seems likely that these phenolic compounds are present in leaves as glycosides and are chieﬂy responsible for the glucuronuria in koalas.