Mass Spectrometric Imaging of Ginsenosides Localization in Panax ginseng Root

Abstract

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 μm 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.