Simultaneous determination of DL-cysteine, DL-homocysteine, and glutathione in saliva and urine by UHPLC-Q-Orbitrap HRMS: Application to studies of oxidative stress

•A highly sensitive UHPLC-HRMS method was provided for the simultaneous analysis of GSH, DL-Cys and DL-Hcy.•D-Hcy was determined in human urine for the first time.•Fitted curves for ratios of D/L-Cys and D/L-Hcy were a convenient and effective method to evaluate oxidative stress.