Relative quantitation of chiral thiol compounds labeled based on isotope novel mass spectrometry probes: Monitoring of the dynamic changes of chiral thiol compounds in human urine during normal, exercise, and rest recovery states

Monitoring changes in the content of chiral thiol compounds in the human body is crucial for the early diagnosis of oxidative stress-related diseases and the exploration of their pathogenesis. To address this, we synthesized a novel isotope mass spectrometry (MS) probe, denoted as ( R )-(5-(3-isothiocyanato ( 13 C) pyrrolidin-1-yl)-5-oxopentyl) triphenylphosphonium (N 13 CS-OTPP), with triphenylphosphine as its parent structure. In this study, we established a new ultra-high-performance liquid chromatography high-resolution mass spectrometry (UHPLC HRMS) relative quantitative method to monitor chiral thiol compounds in human urine under varying oxidative stress conditions. This method relies on the ratio of 12 C/ 13 C isotope-labeled peak areas. To assess the chiral separation efficiency of N 13 CS-OTPP, we employed three types of thiol compounds (D/L-GSH, D/L-Cys, and D/L-Hcy) and observed separation degrees (Rs) ranging from 1.82 to 1.89. We further validated the accuracy and feasibility of our relative quantitative methods using D/L-Cys-as a model compound. N 12 C/ 13 CS-OTPP-Cys-exhibited excellent linearity (R 2 = 0.9993–0.9994) across different molar ratios (D/L-Cys = 10:1, 4:1, 2:1, 1:1, 1:2, 1:4, 1:10) and achieved a low limit of detection (LOD) of 2.5 fmol. Additionally, we monitored the dynamic changes in urine D/L-Cys-and D/L-Hcy ratios in 12 healthy volunteers (six males and six females) under various oxidative stress states. We generated fitting curves and investigated the trends in chiral thiol compounds in vivo . This study introduces a novel method for the relative quantitative monitoring of chiral thiol compounds in different oxidative stress states within the human body. It also presents a new strategy for understanding the pathogenesis of related diseases resulting from the abnormal metabolism of thiol compounds.