Development of a targeted method for twenty-three metabolites related to polyphenol gut microbial metabolism in biological samples, using SPE and UHPLC–ESI-MS/MS

An increasing number of studies have concerned the profiling of polyphenol microbial metabolites, especially in urine or plasma, but only a few have regarded their accurate quantification. This study reports on a new ultra-performance liquid chromatography tandem mass spectrometry method with electrospray ionisation (UHPLC-ESI-MS/MS) using a simple clean-up step with solid phase extraction (SPE) and validation on different biological matrices. The method was tested with spiked samples of liver, heart, kidneys, brain, blood and urine. The purification procedure, after the evaluation of three different cartridges, makes it possible to obtain cleaner samples and better quantification of putative trace metabolites, especially related to dietary studies, with concentrations below ng/g in tissue and for urine and blood, starting from ng/ml. Limits of detection and linear range were also assessed using mixed polyphenol metabolite standards. Short chromatographic separation was carried out for 23 target compounds related to the polyphenol microbial metabolism, coupled with a triple quadrupole mass spectrometer for their accurate quantification. By analysing different spiked biological samples we were able to test metabolite detection in the matrix and validate the overall recovery of the method, from purification to quantification. The method developed can be successfully applied and is suitable for high-throughput targeted metabolomics analysis related to nutritional intervention, or the study of the metabolic mechanism in response to a polyphenol-rich diet.