Desorption electrospray ionization mass spectrometry imaging (DESI-MSI) for the detection of flavan-3-ol metabolites in mimetic model tissues

: Desorption electrospray ionization mass spectrometry imaging (DESI-MSI) provides spatial visualization of compounds directly desorbing from tissue surfaces, although detection efficiency is strongly influenced by instrumental settings, tissue characteristics, and analyte properties. This study optimized key DESI XS ion source parameters, including capillary voltage, heat transfer line temperature, and solvent composition to enhance detection of flavan-3-ol metabolites in biologically relevant tissue mimetic models. Eight mimetic models prepared from animal organs were spiked with (poly)phenol metabolite standards at different concentrations and analyzed under multiple parameter combinations. Results highlighted marked tissue- and metabolite-dependent differences in detection efficiency, with some metabolites remaining undetectable. Using optimized conditions hydroxyphenyl-γ-valerolactone-sulfate-d2 was visualized in liver and kidney tissues following oral gavage of CAT-d4 in mice. This work emphasizes the importance of tailored DESI-MSI parameter optimization to achieve reliable detection of (poly)phenol metabolites with improved sensitivity, thereby supporting a more accurate in situ characterization of their bioavailability and metabolism.