Shinichi Yamaguchi

In situ label-free imaging for visualizing the biotransformation of a bioactive polyphenol

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 detect the naïve molecular localization in mammalian tissues. We herein present a novel in situ label-free imaging technique for visualizing bioactive small molecules, using a polyphenol. We established a 1,5-diaminonaphthalene (1,5-DAN)-based matrix-assisted laser desorption/ionization-mass spectrometry imaging (MALDI-MSI) technique for visualizing epigallocatechin-3-O-gallate (EGCG), the major bioactive green tea polyphenol, within mammalian tissue micro-regions after oral dosing. Furthermore, the combination of this label-free MALDI-MSI method and a standard-independent metabolite identification method, an isotopic fine structure analysis using ultrahigh-resolution mass spectrometer, allows for the visualization of spatially-resolved biotransformation based on simultaneous mapping of EGCG and its phase II metabolites. Although this approach has limitations of the detection sensitivity, it will overcome the drawbacks associated with conventional molecular imaging techniques, and could contribute to biological discovery.

Identification of Drugs by Ultra Fast Liquid Chromatography/Electrospray Ionization‐Quadrupole Ion Trap/Time‐of‐Flight Mass Spectrometry

Abstract Hybrid quadrupole ion trap/time‐of‐flight mass spectrometry (QIT/TOFMS) was applied for detection of ultra fast liquid chromatography (UFLC). The system performance for fast qualitative analysis was evaluated using test drugs. The test drugs were separated on a C18 column (30 mm×2.0 mm I.D., particle size: 2.2 µm) with fast linear gradient elution using 0.1% formic acid and acetonitrile as mobile phase. The flow rate was set at 0.5 mL/min and the analysis cycle time was 4.5 min. Relative standard deviations (RSDs) of retention time and peak area for each drug (200 pg each) were 0.2% or better, lower than 3%, respectively. Mass accuracy of each compound was found to be 3.2 ppm or better. Rapid positive to negative polarity switching mode was demonstrated, showing good mass accuracy below 5 ppm. Moreover, an MS3 measurement was carried out and the formulae of compounds were confirmed using formula prediction software.