A rapid LC-FTMS method for the analysis of cysteine, cystine and cysteine/cystine steady-state redox potential in human plasma

Background: The steady-state redox potential of the cysteine/cystine couple in human plasma provides a measure of oxidative stress, yet available assays are limited by either specificity or speed of assay. Method: The present study evaluated the use of LC-FTMS for identification based on accurate mass combined with quantification by stable isotopic dilution to rapidly determine cysteine and cystine concentration and cysteine/cystine steady-state redox potential in human plasma. Results: A simple extraction procedure followed by a rapid LC separation eluted cysteine in 4 min and cystine in 1.5 min with Simultaneous measurement of glutathione (GSH) and glutathione disulfide (GSSG). A study of five young(mean age=25.7) subjects and 5 older (mean age=67.8 y) subjects showed an increased oxidation with age. Conclusions: The analysis by LC-FTMS is suitable for high-throughput analysis of plasma cysteine, cystine and cysteine/cystine steady-state redox potential as clinical measures of oxidative stress. (c) 2008 Elsevier B.V. All rights reserved.