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 Larrea divaricata Cav., L. cuneifolia Cav. and L. nitida Cav., Zygophyllaceae, are evergreen xerophytic shrubs occurring in Northwestern Argentina used in traditional medicine. The aim of this work was to characterize the morphology, anatomy and histochemistry of the vegetative organs of three Larrea species by light and scanning electron microscopy in order to provide supporting data for their correct identification and to determine the site of synthesis and accumulation of its main active compounds. The shape, number and percentage of coalescence of leaflets, presence or absence of mucrones and rachis and the shape of the stipules represented the main botanical differences between the studied Larrea species. Anatomically three species presented amphystomatic leaves, with thick resinous slightly striated cuticle with resinous deposits, polygonal epidermal cells with straight anticlinal walls, ciclocytic, brachy-paracytic and paracytic stomatal types, non-glandular trichomes and isolateral mesophyll. The position and abundance of the sclerenchyma at the mid vein and petiole transection allows the differentiation of the three species, been more abundant in L. cuneifolia. Secondary phloem and parenchyma cells presented abundant calcium oxalate druses and solitary rhomboidal crystals. Epidermal cells and cuticle layer of leaflets and stipules of the three species presented amber resin deposits and content which stained positively for polysaccharides, phenolic compounds, flavonoids and tannins, while mesophyll palisade cells showed small refracting droplets stained positively for lipophilic substances.