Matrix-assisted laser-desorption/ionization-mass spectrometric imaging of psilocybin and its analogues in psychedelic mushrooms using a cesium chloride-coated target plate

Fungi with hallucinogenic properties and neurotoxicity have been listed as prohibited drugs in recent years, but there is a lack of in situ quantification of psilocybin and analogues in these samples to avoid the decomposition of these psychoactive tryptamines in time-consuming sample preparation. In this study, matrix-assisted laser-desorption/ionization (MALDI)-Fourier transform ion cyclotron resonance (FT ICR) mass spectrometric imaging (MSI) was used to analyze the distribution of psilocybin and its analogues in hallucinogenic Psilocybe mushrooms. A cesium chloride (CsCl)-coated target plate was prepared to improve the detection sensitivity and reduce the interference of other compounds or decomposition products with very similar m/z values in MALDI-FT ICR MS analysis. Psilocybin and other tryptamines with structurally similar compounds, including psilocin, baeocystin, tryptophan, tryptamine, and aeruginascin, were identified and imaged in the psilocybe tissue section; the semiquantitative analysis of the distribution of psilocybin was also investigated using a homemade 75-well CsCl-coated plate; and the target plate can be placed on the mass spectrometry target carrier along with the indium-tin oxide (ITO) conductive slide, which can simultaneously carry out matrix vapor deposition, thus ensuring the parallelism between the standards and samples in the pretreatment experiment and MSI. The contents of psilocybin and its analogues in the psilocybe tissue section can be evaluated from the color changes corresponding to different concentration standard curves. Furthermore, a comprehensive comparison between MALDI-FT ICR MS and ultra-performance liquid chromatography-quadrupole time of flight mass spectrometry (UPLC-Q/TOF MS) analysis was performed for quantification and validation. This study reduces the decomposition in time-consuming sample pretreatment and provides a powerful tool for drug abuse control and forensic analysis.