Study of sample preparation for metabolomic profiling of human saliva by liquid chromatography–time of flight/mass spectrometry

Saliva has recently gained popularity as a potential tool for diagnosis and biomarkers monitoring, as saliva composition may potentially reflect plasma metabolite levels and, therefore, may be used as an indicator of the physiological state. The aim of the present study was to optimize a sample preparation protocol to obtain a metabolite profiling analysis of human saliva by liquid chromatography–time-of-flight/mass spectrometry (LC–TOF/MS) in high-accuracy mode. Under the optimum sample preparation conditions, identification of potential molecular features was carried out. This resulted in 75 compounds tentatively identified from an acidic extract and 33 from an alkaline extract, with a mass tolerance window below 10 ppm. Amino acids, lipids antioxidants and other potentially interesting biomarkers such as polyamines, vitamin B3, and ethylphosphate have been identified. This study covers the gap of knowledge about this biofluid and opens new possibilities for the selection of saliva as source of metabolite biomarkers representative of specific disorders.