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

• Published in: Analytica chimica acta 2006-05, Vol.566 (2), p.157-166
• Main Authors: Mroczek, Tomasz, Ndjoko-Ioset, Karine, Głowniak, Kazimierz, Miętkiewicz-Capała, Agnieszka, Hostettmann, Kurt
• Format: Article
• Language: English
• Subjects: Analytical chemistry; Chemistry; Chromatographic methods and physical methods associated with chromatography; Exact sciences and technology; High-performance liquid chromatography; Ion-trap mass spectrometry; Liquid–liquid partitioning; Other chromatographic methods; Preparative thin-layer chromatography; Pyrrolizidine alkaloids; Spectrometric and optical methods; Symphytum cordatum (L.) W.K
• ISSN: 0003-2670; 1873-4324
• DOI: 10.1016/j.aca.2006.03.016

From the alkalised crude extract of Symphytum cordatum (L.) W.K. roots, pyrrolizidine alkaloids (PAs) were extracted as free tertiary bases and polar N-oxides in a merely one-step liquid–liquid partitioning (LLP) in separation funnel and subsequently pre-fractionated by preparative multiple-development (MD) thin-layer chromatography (TLC) on silica gel plates. In this way three alkaloid fractions of different polarities and retention on silica gel plates were obtained as: the most polar N-oxides of the highest retention, the tertiary bases of medium retention, and diesterified N-oxides of the lowest retention. The former fraction was reduced into free bases by sodium hydrosulfite and purified by LLP on Extrelut-NT3 cartridge. It was further analysed together with the two other fractions by high-performance liquid chromatography (HPLC)–ion-trap mass spectrometry with atmospheric pressure chemical ionization (APCI) interface on XTerra C 18 column using a gradient elution. Based on MS n spectra, 18 various alkaloids have been tentatively determined for the first time in this plant as the following types of structure: echimidine- N-oxide (three diasteroisomers), 7-sarracinyl-9-viridiflorylretronecine (two diasteroisomers), echimidine (two diasteroisomers), lycopsamine (two diasteroisomers), dihydroechinatine- N-oxide, dihydroheliospathuline- N-oxide, lycopsamine- N-oxide (three diasteroisomers), 7-acetyllycopsamine- N-oxide, symphytine- N-oxide (two diasteroisomers) and 2″,3″-epoxyechiumine- N-oxide.