Direct Molecular Analysis of Garlic Using Internal Extractive
Electrospray Ionization Mass Spectrometry
ZHANG Hua, ZHU Liang, CHEN Huan-Wen*
Jiangxi Key Laboratory for Mass Spectrometry and Instrumentation, East China Institute of Technology, Nanchang 330013, China
Abstract: The internal extractive electrospray ionization mass spectrometry (iEESI-MS) has been applied to direct molecular
analysis of garlic tissues. An extraction solvent (e.g., methanol) under a high voltage (+4.5 kV) was injected into the fused silicon
capillary whose far end penetrated into the bulk tissue sample. The chemicals in the bulk tissue were selectively extracted by the
working solvent and carried along the electric field toward the apex of the sample, to generate electrospray in front of an ion trap mass
spectrometer. Without time-consuming sample pretreatment, active garlic substances such as organosulfur compounds (e.g., alliin,
allicin), amino acids (e.g., arginine) and saccharides (glucose, polysaccharides) were successfully detected and directly identified via
collision-induced dissociation (CID) in positive ion detection mode. Mass spectral fingerprints of different kinds of garlic cloves (24
samples), as well as various post-treated ones (36 samples) in the range of m/z 50–2000 Da, were classified via principal component
analysis (PCA). The experimental results indicated that iEESI-MS allowed direct identification of chemical components in garlic
tissue and rapid recognition of metabolic changes in the garlic tissue subjected to various external stimuli, with the analytical
advantages such as simplicity, rapidity (less than 2 min per sample), good specificity, and minimal disturbance to the bioactivity of