TABLE 2

Diagnostic MS/MS product ions used to propose metabolite structures

Metabolite NameProposed Structure with Assigned MS/MS Product IonsPrecursor IonDiagnostic MRM Product Ions*
P19Embedded Image567†171, 203, 373‡,§
P26.9Embedded Image409143, 171, 188‡,,‖
P30.3Embedded Image409143, 171, 188‡,‖
P37Embedded Image569173, 188, 375‡
P37.7Embedded Image569173, 188, 375
P38.2Embedded Image248117, 145, 173‡
P39Embedded Image19091, 117, 129‡

  • ↵* Due to the low metabolite concentrations in this study, the mass spectrometric analysis of the samples was performed in the MRM mode rather than the full-scan product ion mode to insure sufficient sensitivity. Additional details can be found in the Materials and Methods.

  • ↵† Although the actual protonated molecular weight of M19 is 585 Da, m/z 567 was chosen as the precursor ion, because M19 was found to readily lose a molecule of water in the mass spectrometer ion source.

  • ↵‡ Mass spectrometric and chromatographic retention time matching with a synthetic standard provided additional structural confirmation.

  • ↵§ The standard for M19 was generated via incubation with UGT1A1 of a synthetic standard for P26.9.

  • ↵ Comparison of NMR spectrum with that of a synthetic standard provided additional structural confirmation.

  • ↵‖ Four individual diastereomeric standards were synthesized.