Detection of Coffee Polyphenols in Nanoliter Cerebrospinal Fluid by Microextraction Coupled to Nanoelectrospray Ionization Mass Spectrometry

An analytical technique was designed and constructed for the in situ extraction and rapid qualitative and quantitative detection of polyphenols in nanoliter cerebrospinal fluid. By preparing polypyrrole microextraction probes with good biocompatibility and stability, the rapid and efficient enrichment of polyphenols in cerebrospinal fluid was achieved, and the matrix interference was reduced. Combined with nanoelectrospray ionization mass spectrometry ( nESI-MS ), high-throughput rapid detection of polyphenols in micro-volume mice cerebrospinal fluid was realized. The method for simultaneous detection of four phenolic acids(caffeic acid, 3-hydroxyphenylacetic acid, homovanillic acid and ferulic acid) and two flavonoids(epicatechin and epigallocatechin gallate) was established based on microextraction coupled to nESI-MS. The linear ranges were 0.1/0.5/1-20 mu g/mL(R-2=0.994-0.999) with recovery rates in the cerebrospinal fluid matrix of 96.9%-108%, and the detection limits were 0.027-0.39 mu g/mL(0.014- 0.20 ng), which took the advantages of low sample consumption, wide linear range, low detection limit and accurate quantification. In addition, the new method was utilized to analyze the content and dynamic changes of polyphenols in mice cerebrospinal fluid after polyphenol ingestion, which showed high potential application value in understanding the distribution and metabolism of polyphenols in cerebrospinal fluid and exploring their mechanism in neuroprotection.