New Insights Into the Chemical Composition of Baccharis palustris Heering (Asteraceae) Essential Oil

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-center dot 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 UV lambda= 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 [alpha-pinene epoxide, rosefuran, epi-cubebol, cubebol, germacrene D-4-ol, junenol, epi-alpha-cadinol, epi-alpha-muurolol, germacra-4(15),5,10(14)-trien-1-beta-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.