Abstract B. palustris Heering (Asteraceae), has been previously characterized as having an unusual essential oil composition with C9-/C10-polyacetylenes as main components, and mono- and ...sesqui-terpenes/terpenoids at minor or trace levels. In this work, new insights into the chemical composition of this oil are presented: 1. TLC profiles using different visualization reagents for their characterization, 2. chemical analyses combining HRGC/qMS, HRGC/HRMS-TOF and HRGCxHRGC/HRMS-TOF, and 3. radical scavenging activity assay using the DPPH methodology were performed. The best TLC visualization conditions for the polyacetylenic components of the oil were obtaining using UVλ= 365 nm and vanillin/H3PO4, while the original application of NaDi (1-naphtol + N,N-dimethyl-p-phenylendiamine) demonstrated to be the best option to visualize the lachnophyllum acid methyl esters fraction. Gas chromatography/mass spectrometry protocols allowed the detection of 63 components in B. palustris oil: 39 of them were identified, 6 tentatively assigned without LRI information, and 18 could not be identified. Most of the identified components were mono- and sesquiterpenes and their derivatives. Ten of them are informed for the first time in B. palustris oil α-pinene epoxide, rosefuran, epi-cubebol, cubebol, germacrene D-4-ol, junenol, epi-α-cadinol, epi-α-muurolol, germacra-4(15),5,10(14)-trien-1-β-ol and oplopanone. C9-/C10-polyacetylenes (baccharisdyine/lachnophyllum acid derivatives) were confirmed as the main components of the oil, while other polyacetylenes were tentatively identified and their possible structures are discussed. The deconvolution analyses on HRGCxHRGC/HRMS-TOF allowed the identification of a lachnophyllum lactone isomer (undefined stereochemistry), co-eluting with the (cis)-lachnophyllum acid methyl ester peak. Finally, B. palustris oil was found to be an inactive DPPH radical scavenger.
Abstract Morphoanatomy and histochemistry of Baccharis palustris: insights into a highly endangered endemic species from Southeastern America. The phenotypic plasticity of the Baccharis genus makes ...species identification difficult, even at the flowering stage. In this context, morphoanatomical studies are a powerful tool for botanical authentication, mainly emphasizing the recognition of diagnostic characteristics that may be useful for distinguishing similar species. Given the limited knowledge available about the endemic species B. palustris, this work aimed to characterize the morphoanatomy and histochemistry of its vegetative aerial parts to identify characters with diagnostic value and to elucidate the sites of synthesis and accumulation of metabolites of medicinal importance. B. palustris leaf showed pinnate, camptodrome-brochidodrome venation patterns. Blade with dorsiventral mesophyll, aerenchymatous spongy parenchyma, collateral vascular bundles, and different types of stomata and trichomes, including glandular trichomes with a multi-layered base evidenced and described for the first time in the genus. The petiole was winged, with three collateral vascular bundles. The stem showed a penta-lobulated contour with unusual growth, starch, and crystals in the pith. The presence of secretory ducts and glandular trichomes, which synthesized lipids, terpenes/polyacetylenes, and phenolic compounds, was observed. The morphological/histochemical characteristics described in this work contribute to the knowledge of the species, highlighting the importance of its preservation as a valuable resource.
Resumen Morfoanatomía e histoquímica de Baccharis palustris: ampliando el conocimiento de una especie endémica altamente amenazada del sureste de América. La plasticidad fenotípica del género Baccharis dificulta la identificación de las especies, incluso en la etapa de floración. En este contexto, la descripción morfoanatómica es una herramienta poderosa para la autenticación botánica, haciendo hincapié en las características de valor diagnóstico que pueden ser útiles para distinguir especies similares. Dado el escaso conocimiento disponible sobre la especie endémica B. palustristis, el objetivo de este trabajo fue caracterizar la morfoanatomía y la histoquímica de las partes aéreas vegetativas de B. palustris y establecer los sitios de síntesis y acumulación de metabolitos de importancia medicinal. La hoja de B. palustris mostró venación pinnada, camptódroma, broquidódromo. Lámina con mesofilo dorsiventral con parénquima esponjoso aerenquimático, haces vasculares colaterales y distintos tipos de estomas y tricomas, entre los que se destacan tricomas glandulares de base pluriceriada nunca antes descriptos para el género. El pecíolo se presentó alado, con tres haces vasculares colaterales. El tallo mostró contorno pentalobulado con crecimiento poco usual, almidón y cristales en la médula. Se observó la presencia de conductos secretores y tricomas glandulares, los cuales pueden sintetizar lípidos, terpenos/poliacetilenos y compuestos fenólicos. Las características morfológicas/histoquímicas descritas en este trabajo contribuyen al conocimiento de la especie, destacando la importancia de su preservación como un recurso valioso.
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