Investigation of Symphytum cordatum alkaloids by liquid–liquid partitioning, thin-layer chromatography and liquid chromatography–ion-trap mass spectrometry

Simultaneous characterization of pyrrolizidine alkaloids and N‐oxides in Gynura segetum by liquid chromatography/ion trap mass spectrometry

“…Fortunately, the advent of the chromatography/tandem mass spectrometry protocol has thrown some light on the exploitation of complicated minor PAs and PANOs originating from plants and diets. However, in gas chromatographic (GC) analysis the thermal decomposition of labile N ‐oxides and sometimes also of diesterified PAs is frequently observed 11. For these reasons, high‐performance liquid chromatography/mass spectrometric (HPLC/MS) analyses of PAs and PANOs were often previously reported,11–19 which will aid the elucidation of unknown compounds of this class.…”

“…However, in gas chromatographic (GC) analysis the thermal decomposition of labile N ‐oxides and sometimes also of diesterified PAs is frequently observed 11. For these reasons, high‐performance liquid chromatography/mass spectrometric (HPLC/MS) analyses of PAs and PANOs were often previously reported,11–19 which will aid the elucidation of unknown compounds of this class. In sample preparation, some solid‐phase extraction (SPE) protocols have already been published 11, 17, 20.…”

The Chemical Profile of Pyrrolizidine Alkaloids from Selected Greek Endemic Boraginaceae Plants Determined by Gas Chromatography/Mass Spectrometry

“…The CH 2 Cl 2 layer containing the free PAs was condensed and analyzed. The neutralized second aqueous layer was evaporated, and the obtained residue was reduced, using either zinc suspension in 2 M HCl (31) or Na 2 S 2 O 4 in dilute HCl (24). The latter method is recommended because of the shorter reaction time needed (30 min versus several hours or overnight) and the less acidic solution used (0.05 M HCl) so as to avoid hydrolysis of PAs.…”

“…Although silica is the main component of diatomaceous earth and is a known adsorbent of acidic nature that is expected to retain free PAs, no quantitative estimation regarding the recovery effectiveness of this method is reported. As regards N-oxide reduction, zinc suspension in acidic solution is most frequently used (10,22,23), while an acidic solution of sodium dithionite is an alternative reducing agent (21,24). The preparation and application of an indigocarmine redox resin, activated by a 5% sodium dithionite solution, has also been described (25).…”

Isolation of the Pyrrolizidine Alkaloid Intermedine-N-oxide from Cerinthe glabra and ab initio Calculation of its 13C NMR Shifts

“…But these techniques suffer from some shortcomings: Since PA N-oxides are quite unstable, they decompose under GC conditions, consequently GC analysis can only be performed on the free PA, obtained by reduction of the native N-oxides with zinc/sulfuric acid [10] or with new, milder reagents like sodium hydrosulfite [11] and indigocarmine-based redox resins [5,12]. Further, isomeric PA like the alkaloids intermedine, lycopsamine, echinatine, rinderine, and indicine (and likewise the corresponding Nc 2012 Verlag der Zeitschrift für Naturforschung, Tübingen · http://znaturforsch.com Fig.…”