Analysis of Erythroxylum coca Leaves by Imaging Mass Spectrometry (MALDI–FT–ICR IMS)

Abstract

Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI IMS) can determine the chemical identity and spatial distribution of several molecules in a single analysis, conserving its natural histology. However, there are no specific studies on the spatial distribution of alkaloids in Erythroxylum coca leaves by MALDI IMS, preserving the histology of the monitored compounds. Therefore, in this work, positive-ion mode MALDI Fourier-transform ion cyclotron resonance imaging mass spectrometry (MALDI­(+)­FT–ICR IMS) was applied to identify and analyze the distribution of alkaloids on the surface of coca leaves, evaluating the ionization efficiency of three matrices (α-cyano-4-hydroxycinnamic acid (CHCA), 2-mercaptobenzothiazole (MBT), and 2,5-dihydroxybenzoic acid (DHB)). The last was chosen as the best matrix in this study, and it was studied in five concentrations (0.5, 1.0, 2.0, 4.0, and 8.0 mg·mL–1), where 2 mg·mL–1 was the most efficient. The washing of coca leaves with the organic solvents (acetonitrile, methanol, toluene, and dichloromethane) tested did not improve the performance of the ionization process. Finally, a tissue section, 50 μm thick, was used to study the inner part of the leaf tissue, where alkaloids and flavonoid molecules were detected.

Analysis of Gliricidia sepium Leaves by MALDI Mass Spectrometry Imaging

“…The conditions applied were the nebulizer gas pressure of 1.0 bar, a capillary voltage of 3.6 kV, and a capillary transfer temperature of 250 °C. In the ion transmission, ion accumulation times and TOF were 0.035 s and 0.9 ms, respectively …”

“…To compare the efficiency of different matrices and a matrix-free environment, the equipment was calibrated externally. The analyses were carried out on the same day, and the samples were spotted on the same plate. , …”

“…In the ion transmission, ion accumulation times and TOF were 0.035 s and 0.9 ms, respectively. 24 Collision-induced dissociation (CID) experiments were performed using an LTQ-XL, linear ion trap mass spectrometer (Thermo Fisher Scientific, USA), containing a heated electrospray ionization source HESI (heated electrospray ionization) and a normalized collision energy (13−28%).…”

“…The analyses were carried out on the same day, and the samples were spotted on the same plate. 4,24 For MALDI(−)MSI measurements, the FT-ICR mass spectrum was accumulated by 100 laser shots per pixel, with a spatial resolution of 150 μm and an average laser intensity of 80%. Finally, image and spectral data were processed with Flex Imaging 3.0 software and data analysis software (Bruker).…”

Interpol Review of Drug Analysis 2019-2022

“…2020 new variety of Erythroxylum from Peru [ 305 ]; 2021 MALDI(+)FT-ICR-IMS for analysis of the distribution of alkaloids on the surface of coca leaves [ 306 ]; cytotoxicity evaluation studies performed with extracts or pure substances obtained from Erythroxylum species [ 307 ]; Qualitative phytochemical analysis followed by HPTLC analysis of the leaves of Erythroxylum moonii Hochr [ 308 ].…”