Simultaneous LC-MS/MS quantification of glucocorticoids, melatonin and its metabolites in hair.

BACKGROUND: The long-term sleep state has an important influence on one's physical and mental health. Melatonin (MEL) and cortisol with circadian rhythm are deemed to be potential sleep biomarkers. Considering the rapid metabolism of MEL and cortisol, their main metabolites could be alternative indicators showing higher stability and reliability. However, there is short of research developing the method for simultaneous quantification of MEL, cortisol and their metabolites in hair. OBJECTIVES: This study aimed to develop a method for the simultaneous quantification of F, MEL and their main metabolites (cortisone; N-acetyl-serotonin, NAS; 6-hydroxymelatonin, 6-O-MEL and 6-sulfatoxymelatonin, S-O-MEL) in human hair based on high-performance liquid chromatography tandem mass spectrometry method, and then explore the relationship between the biomarkers' contents and sleep state. METHODS: Analytes were extracted from 20-mg hair in 1 mL methanol at about 27°C, and then analyzed in a mobile phase of 95% methanol and 5% 5 mM ammonium acetate, and identified with an electrospray ionization source in positive ion mode. Hair samples closest to the scalp were collected from 65 undergraduates. Sleep state was measured based on participants' scores of the Pittsburgh Sleep Quality Index, the Epworth Sleepiness Scale and the Morningness/Eveningness Questionnaire. RESULTS: The method showed good linearity with the square of correlation coefficient > 0.99 at the ranges of 0.1-1000 pg/mg for MEL, 0.4-1000 pg/mg for NAS, 1.0-1000 pg/mg for 6-O-MEL, 1.0-1000 pg/mg for S-O-MEL, 0.5-1000 pg/mg for cortisol and 1.0-1000 pg/mg for cortisone. It showed the limit of detection ranged from 0.05 to 0.3 pg/mg and the limit of quantification ranged between 0.1 and 1.0 pg/mg for the six analytes. The inter- and intra-day coefficients of variation were < 20%. The compounds could be detected in natural hair samples except for S-O-MEL. The average concentration was 0.18 pg/mg for MEL, 3.5 pg/mg for NAS, 3.8 pg/mg for 6-O-MEL, 20.0 pg/mg for cortisone and 2.8 pg/mg for cortisol. The population analysis revealed that there was positive association between hair cortisone and sleep quality. CONCLUSIONS: This study had developed an LC-MS/MS method for simultaneous quantification of MEL, NAS, 6-O-MEL, cortisone and cortisol in human hair. Hair cortisone might be a promising biomarker of long-term sleep state.