The buds of poplars (Populus L.) and willows (Salix L.), both from the same family (Salicaceae Mirbel), are increasingly used in gemmotherapy and importantly contribute to the production of the physiologically active propolis by European bee Apis mellifera L. In order to study their phenolic profiles, polar extracts of buds from P. nigra L. were compared to those of P. alba L. and S. alba L. through high-performance thin-layer chromatography (HPTLC). Five chemotypical patterns were distinguished after derivatisation with the Natural Product reagent and confirmed by principal component analysis. The HPTLC analysis was directly hyphenated to various microbiological and biochemical assays as well as spectrometric techniques, directly linking to active molecules in the chromatograms. At a glance, polyvalent compounds were evident when all derivatisation and activity assays, to which HPTLC was hyphenated at ease, were combined together. In Populus buds, at least three antimicrobial compound zones were detected using Aliivibrio fischeri and Bacillus subtilis bioassays, and one phyto-œstrogen with the planar yeast œstrogen screen. In all samples, several inhibitors of acetyl- and butyrylcholinesterase and rabbit liver esterase were detected. Hyphenation to high resolution mass spectrometry supported the assignment of bioactive compounds, as shown for chrysin as selective cholinesterase inhibitor as well as caffeic acid and galangin as antimicrobials in P. nigra and P. alba. This fast and cost-efficient method can be appropriately extended and applied to the botanical origin determination and quality control of bud extracts and propolis samples.
Keywords: Bioprofiling; Bud sap extracts; HPTLC–MS; Populus alba; Populus nigra; Salix alba.
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