IDENTIFICATION AND MEASUREMENT OF OXINDOLE (2-INDOLINONE) IN THE MAMMALIAN BRAIN AND OTHER RAT ORGANS

Oxindole, a putative tryptophan metabolite able to cause profound seda tion when administered in relatively low doses to mammals, has been id entified and measured in the brains of mice, rats, and guinea pigs usi ng HPLC and GC/MS with a quadrupole ion trap and a collision-induced d issociation mass spectrometer. The identification and measurement of t he compound required a protein precipitation step with HClO4, extracti on into chloroform, an HPLC separation on a reverse-phase column, and detection by UV or coulometry. The definitive identification of the ox indole peak was obtained with a Saturn 4D GC/MS quadrupole ion trap op erated under GC/MS, GC/MS/MS, and GC/MS/MS/MS modes. The HPLC methods we used had a low interassay variability, easily allowing the identifi cation and measurement of the compound in 1 g of tissue. The oxindole concentrations in rat brain, blood, liver, and kidney were each approx imately 100 pmol/g wt. Interestingly, the content of oxindole in the g uinea pig brain was found to be significantly lower than that in the m ouse and rat brains, possibly reflecting a lower dietary intake of try ptophan in the guinea pigs. (C) 1997 Academic Press, Inc.