Yuko Sahashi

Mass Spectrometric Imaging of Ginsenosides Localization in Panax ginseng Root

We performed mass spectrometric imaging (MSI) to localize ginsenosides (Rb(1), Rb(2) or Rc, and Rf) in cross-sections of the Panax ginseng root at a resolution of 100 microm using matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS). Tandem mass spectrometry (MS/MS) of alkali metal-adducted ginsenoside ions revealed structural information of the corresponding saccharides and aglycone. MALDI-MSI confirmed that ginsenosides were located more in the cortex and the periderm than that in the medulla of a lateral root. In addition, it revealed that localization of ginsenosides in a root tip (diameter, 2.7 mm) is higher than that in the center of the root (diameter, 7.3 mm). A quantitative difference was detected between localizations of protopanaxadiol-type ginsenoside (Rb(1), Rb(2), or Rc) and protopanaxatriol-type ginsenoside (Rf) in the root. This imaging approach is a promising technique for rapid evaluation and identification of medicinal saponins in plant tissues.

Nanotrap and Mass Analysis of Aromatic Molecules by Phenyl Group-Modified Nanoparticle

To functionalize the surface of nanoparticles with phenyl groups for subsequent cross-linking with aromatic molecules by mutual interactions, we prepared functional nanoparticles (d = 3 nm) by silanization with phenyl-triethoxysilane. The nanoparticles had Fe(2)O(3) cores conjugated to phenyl groups; this was confirmed by Fourier transform infrared (FT-IR) spectroscopy and absorption spectrophotometry. The typical C-H and C-C peaks and the absorption at 240 nm, which corresponds to aromatic rings, were detected in the spectroscopic results for the phenyl group-modified nanoparticles. The nanoparticles could ionize aromatic (colchicine, reserpine, and bradykinin peptide) and nonaromatic (L-α-phosphatidylethanolamine,dioleoyl, and polyethylene glycol) molecules by nanoparticle-assisted laser desorption/ionization mass spectrometry. The nanoparticles worked as a selective trap and an ionization-assisting reagent in mass spectrometry for the aromatic molecular targets.