Determination of glycoalkaloids and relative aglycones by nonaqueous capillary electrophoresis coupled with electrospray ionization-ion trap mass spectrometry

Abstract

Glycoalkaloids are naturally occurring nitrogen-containing compounds present in many species of the family Solanaceae, including cultivated and wild potatoes (Solanum spp.), tomatoes (Lycopersicon spp.), etc. These compounds have pharmacological and toxicological effects on humans due to their significant anticholinesterase activity and disruption of cell membranes. Herein is reported the development of a capillary electrophoresis (CE) method using nonaqueous (NA) separation solutions in combination with ion trap mass spectrometry (MS and MS/MS) detection for the identification and quantification of glycoalkaloids and their relative aglycones. A mixture 90:10 v/v of MeCN-MeOH containing 50 mM ammonium acetate and 1.2 M acetic acid (applied voltage of 25.5 kV) was selected as a good compromise for the separation and detection of these compounds. The electrospray MS measurements were carried out in the positive ionization mode using a coaxial sheath liquid, methanol-water (1:1) with 1% of acetic acid at a flow rate of 2.5 microL/min. Under optimized experimental conditions, the predominant ion was the protonated molecular ion ([M+H](+)) of solanidine (m/z = 398), tomatidine (m/z = 416), chaconine (m/z = 852), solanine (m/z = 868), and tomatine (m/z = 1034). MS/MS experiments were carried out systematically by changing the relative collisional energy and monitoring the intensities of the fragment ions that were not high enough to allow better quantification than with the mother ions. The method was used for analyzing glycoalkaloids in potato extracts.

Separation Technology as a Powerful Tool for Unfolding Molecular Complexity of Natural Organic Matter and Humic Substances

“…The addition of organic solvents to the running buffer (up to 100% in case of nonaqueous CE), can improve the solubility of some analytes. This approach is often used for separation of pharmaceuticals or plant secondary metabolites (Bianco et al, 2002 ). The selectivity is governed by their effective charge and thus by the separation buffer pH and the electroosmotic fl ow (EOF).…”

Development of Practical HPLC Methods for the Separation and Determination of Eggplant Steroidal Glycoalkaloids and their Aglycones

“…[44] Several authors have explored novel methods for the determination of glycoalkaloids in recent years. Among these are the use of enzyme-linked immunosorbent assay (ELISA), which is useful only for the aglycone forms, [45] "fluorescence polarization immunoassay," [46] "solution phase immunoassay with capillary electrophoresis, [47] gas chromatography mass spectrometry as applied to the aglycone forms, [48] liquid chromatography mass spectrometry, [38,49] matrix-assisted laser-desorption/ ionization time-of-flight mass spectrometry (MALDI-TOF/MS), [50] "nonaqueous capillary electrophoresis with ultra violet (UV) detection (NACE-UV)" for the analysis of solasodine and solanidine aglycones, [51,52] NACE combined with ion-trap mass spectrometry, [52,53] and, lastly, derivatization of the glycoalkaloids followed by HPLC separation and chemiluminescence detection. [54] Each of these methods has its own particular merits; however, although glycoalkaloids show limited absorption of ultraviolet (UV) light, HPLC separation followed by UV detection can still be considered a viable method, due to the relative widespread availability of this instrumentation and the potential to detect not some, but all the glycoalkaloids of interest without a lengthy derivatization step.…”

Evaluation of glycoalkaloids in tubers of genetically modified virus Y-resistant potato plants (var. Désirée) by non-aqueous capillary electrophoresis coupled with electrospray ionization mass spectrometry (NACE–ESI–MS)

“…Désirée) were compared. A very recently proposed analytical methodology was employed, which is based on non-aqueous capillary electrophoresis (NACE) coupled on-line with electrospray ionization mass spectrometry (ESI-MS and ESI-MS 2 ) in the positive ion mode [24].…”