Location: Poisonous Plant ResearchTitle: Recognition of pyrrolizidine alkaloid esters in the invasive aquatic plant Gymnocoronis spilanthoides (Asteraceae) Author
|Boppre, Michael - Albert University Of Freiburg|
Submitted to: Phytochemical Analysis
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/13/2014
Publication Date: 5/1/2015
Publication URL: http://handle.nal.usda.gov/10113/62770
Citation: Boppre, M., Colegate, S.M. 2015. Recognition of pyrrolizidine alkaloid esters in the invasive aquatic plant Gymnocoronis spilanthoides (Asteraceae). Phytochemical Analysis. 26(3):215-225. Interpretive Summary: The presence of potentially toxic dehydropyrrolizidine alkaloid esters in the neotropical, freshwater aquatic plant Gymnocoronis spilanthoides was indicated by attraction of pyrrolizidine alkaloid-pharmacophagous butterflies to the plant. HPLC-esi(+)MS and MS/MS analysis of the alkaloidal fraction from a methanolic extract of the plant confirmed the presence of the dehydropyrrolizidine alkaloids lycopsamine, intermedine and rinderine along with several other more minor pyrrolizidine and dehydropyrrolizidine alkaloids. Tentative structures for two new pyrrolizidine alkaloids are proposed. The presence of the toxic alkaloids in this invasive plant presents an additional consideration with regards to management and control of the plant.
Technical Abstract: Introduction – The freshwater aquatic plant Gymnocoronis spilanthoides (Senegal tea plant, jazmín del bañado, Falscher Wasserfreund) is an invasive plant in many countries. Behavioural observations of pyrrolizidine alkaloid-pharmacophagous butterflies suggested the presence of pyrrolizidine alkaloids in the plant. Objective – To determine whether the attraction of the butterflies to the plant is an accurate indicator of pyrrolizidine alkaloids in G. spilanthoides. Methods – The alkaloid fraction of a methanolic extract of G. spilanthoides was analysed using HPLC with electrospray ionisation MS and MS/MS. Two HPLC approaches were used, that is, a C18 reversed-phase column with an acidic mobile phase, and a porous graphitic carbon column with a basic mobile phase. Results – Pyrrolizidine alkaloids were confirmed, with the free base forms more prevalent than the N-oxides. The major alkaloids detected were lycopsamine and intermedine. The porous graphitic carbon HPLC column, with basic mobile phase conditions, resulted in better resolution of more pyrrolizidine alkaloids including rinderine, the heliotridine-based epimer of intermedine. Based on the MS/MS and high-resolution MS data, gymnocoronine was tentatively identified as an unusual C9 retronecine ester with 2,3-dihydroxy-2-propenylbutanoic acid. Among several minor-abundance monoester pyrrolizidines recognised, spilanthine was tentatively identified as an ester of isoretronecanol with the unusual 2-acetoxymethylbutanoic acid. Conclusions – The butterflies proved to be reliable indicators for the presence of pro-toxic 1,2-dehydropyrrolizidine alkaloids in G. spilanthoides, the first aquatic plant shown to produce these alkaloids. The presence of the anti-herbivory alkaloids may contribute to the plant’s invasive capabilities and would certainly be a consideration in any risk assessment of deliberate utilisation of the plant. The prolific growth of the plant and the structural diversity of its pyrrolizidine alkaloids may make it ideal for investigating biosynthetic pathways or for large-scale production of specific alkaloids.