Post-column sodiation to enhance the detection of polyacetylene glycosides in LC–DAD–MS analyses: an example from Bidens gardneri (Asteraceae)

• A methodology to analyze polyacetylenes by LC–ESI–MS.
• Post-column sodiation to enhance the detection.
• New polyacetylenes were isolated by phytochemical procedures guided.
• The structures of the isolated polyacetylenes have been confirmed by 1D and 2D NMR, HRMS.

The use of liquid chromatography–electrospray ionization–mass spectrometry (LC–ESI–MS) in dereplication studies of medicinal plants is a common strategy, but the analyses of polyacetylenes by LC–ESI–MS are little explored and require huge efforts, especially if there are low concentrations in the extracts. A post-column sodiation strategy was successfully applied to enhance the detection of polyacetylene glycosides. Their molecular formulae were proposed by HRESI, whereas the polyacetylene chromophores were determined by UV data. The use of acetic acid in the mobile phase was essential to obtain satisfactory chromatographic resolution, and only the addition of sodium chloride solution allowed good mass spectra, internal calibration and undoubtedly the molar mass determination of polyacetylenes. This new approach has allowed the identification of polyacetylene glycosides from Bidens gardneri extract, guiding the isolation procedures, and two new compounds were obtained. The structures of the isolated polyacetylenes have been confirmed by 1D and 2D NMR, HRMS.

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