Direct Molecular Analysis of Garlic Using Internal Extractive Electrospray Ionization Mass Spectrometry

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 analytes.

Without any sample pretreatment, internal extractive electrospray ionization mass spectrometry (Ieesi-MS) in combination with principal component analysis (PCA) allowed direct molecular characterization of internal chemicals in bulk garlic tissues specific to sort and various environmental stimuli.Figure optionsDownload as PowerPoint slide