Fig. 2.

Targeted analysis confirms urinary etiocholan-3a-ol-17-one sulfate as a IC/BPS subgroup biomarker. (a) Targeted analysis reveals a significantly higher ratio of m/z 369¹⁸ to m/z 369²⁰ in IC/BPS subgroup 2 compared to subgroup 1 and non-IC/BPS controls (p = 0.0003 and 0.0022, respectively, t-test). Likewise, levels of m/z 369 were higher in subgroup 1 compared to non-IC/BPS controls (p = 0.0071, t-test). (b) High-resolution positive ion ESI mass spectrum is consistent with the empiric formula C₁₉H₃₀O₅S for a [M − H]⁻ species with a difference of − 2.18 ppm. (c) High-resolution negative ion tandem ESI spectrum of the candidate biomarker is consistent with the empiric formula C₁₉H₃₀O₅S ([M − H]⁻ at m/z 369.1745) that fragments to give a peak at m/z 96.9597, consistent with the presence of a sulfate group with the empiric formula SO₄H. (d) Matching GC-EI-MS spectra of this sulfatase-treated, TMS-derivatized analyte compared to a commercially available reference standard. Retention time for both the analyte and standard was 21.8 min.