A Strategy for Label-free Visualization of Tissue Distribution of Green Tea Polyphenols Using Mass Spectrometry Imaging Technique

Abstract

Although understanding the high-resolution spatial distribution of bioactive small molecules is indispensable for elucidating their biological or pharmacological effects, there has been no analytical technique that can easily visualize the naïve molecular localization in mammalian tissues. In this review, we represent a novel in situ label-free imaging technique of bioactive small molecules, such as polyphenol. A matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) technique visualized epigallocatechin-3-O-gallate (EGCG), the major bioactive green tea polyphenol, within mouse tissue micro-regions after oral dosing. Furthermore, the combination of this label-free MALDI-MSI method and a standard-independent metabolite identification method allowed for the visualization of spatially-resolved biotransformation based on simultaneous mapping of EGCG and its phase II metabolites. This approach will overcome the drawbacks associated with conventional molecular imaging techniques, and could contribute to biological discovery.