Volatile Constituents of Achillea ligustica All. by HS-SPME/GC/GC-MS. Comparison with Essential Oils Obtained by Hydrodistillation from Corsica and Sardinia

The volatile components extracted from the headspace (HS) of Achillea ligustica All. samples and their separated organs using solid phase microextraction (SPME) were investigated by gas chromatography and gas chromatography-mass spectrometry. Fiftyseven compounds were identified, the main components were camphor (14.2–29.8%), artemisia ketone (0.3–26.7%), santolina alcohol (0.5–9.4%), camphene (3.0–9.0%) and trans-sabinyl acetate (1.6–5.5%). Moreover, the chemical composition of Corsican and Sardinian A. ligustica oils obtained from flowers and leafy stems harvested in four regions of both islands, were investigated. Two collective oils of A. ligustica were also investigated, comparison between both oils as well as from data literature were reported. A comparison of hydrodistillation and HS-SPME extraction of volatile components in term of isolation time, plant-consuming and chemical composition was discussed. HS-SPME technique was clearly fast in contrast to hydrodistillation (90 min/300 min). HS extraction was performed with a much smaller amount of plant than hydrodistillation. Although the aromatic profiles of HS-fractions and oils showed several quantitative differences HS-SPME can be applied to routine control analysis of aromatic and medicinal plants.

     

Spectral data of two new asymmetric sesquiterpene alcohols: (14R)-beta-oplopenol and (14S)-beta-oplopenol

The epimeric sesquiterpene alcohols (14R)-beta-oplopenol and (14S)-beta-oplopenolwere obtained by LiAlH(4) reduction of beta-oplopenone. The complete (1)H- and (13)C-NMR assignments of these two new sesquiterpene alcohols have been made using 1D and 2D NMR techniques, including COSY, NOESY, HSQC, HMBC experiments.     

Guaianolide Derivatives from the Invasive Xanthium spinosum L.: Evaluation of Their Allelopathic Potential

Ziniolide, xantholide B (11α-dihydroziniolide), and 11β-dihydroziniolide, three sesquiterpene lactones with 12,8-guaianolide skeletons, were identified as volatile metabolites from the roots of Xanthium spinosum L., an invasive plant harvested in Corsica. Essential oil, as well as hydrosol and hexane extracts, showed the presence of guaianolide analogues. The study highlights an analytical strategy involving column chromatography, GC-FID, GC-MS, NMR (1D and 2D), and the hemi-synthesis approach, to identify compounds with incomplete or even missing spectral data from the literature. Among them, we reported the ¹H- and ¹³C-NMR data of 11β-dihydroziniolide, which was observed as a natural product for the first time. As secondary metabolites were frequently involved in the dynamic of the dispersion of weed species, the allelopathic effects of X. spinosum root’s volatile metabolites were assessed on seed germination and seedling growth (leek and radish). Essential oil, as well as hydrosol- and microwave-assisted extracts inhibited germination and seedling growth; root metabolite phytotoxicity was demonstrated. Nevertheless, the phytotoxicity of root metabolites was demonstrated with a more marked selectivity to the benefit of the monocotyledonous species compared to the dicotyledonous species. Ziniolide derivatives seem to be strongly involved in allelopathic interactions and could be the key to understanding the invasive mechanisms of weed.     

Antibacterial Mode of Action of the Daucus carota Essential Oil Active Compounds against Campylobacter jejuni and Efflux-Mediated Drug Resistance in Gram-Negative Bacteria

Today, an alarming rise of bacterial gastroenteritis in humans resulting from consuming Campylobacter-tainted foods is being observed. One of the solutions for mitigating this issue may be the antibacterial activity of essential oils. In the present research, we propose to study the antibacterial activity against Campylobacter and other Gram-negative bacteria of Daucus carota essential oil and its active molecules. In addition, a few chemically synthesized molecules such as (E)-methylisoeugenol, Elemicin, and eugenol were also studied. The results showed that the essential oil itself and its most active component, (E)-methylisoeugenol, exhibited bactericidal effects. Similar effects were detected using purified and chemically synthesized molecules. Also, it was observed that the Daucus carota essential oil and its active molecules affected intracellular potassium and intracellular ATP contents in Campylobacter cells. Inhibition of the membrane bound F_OF₁-ATPase was also observed. Eventually, for the first time, the efflux mechanism of active molecules of Daucus carota essential oil was also identified in gamma proteobacteria and its specific antibacterial activity against Campylobacter jejuni was associated with the lack of this efflux mechanism in this species.     

A Theoretical Approach to Restart in Global Optimization

While searching for the global minimum of a cost function we haveoftento decide if a restart from a different initial point would bemoreadvantageous than continuing current optimization. This is aparticularcase of the efficiency comparison between repeatedminimizations and singleextended search having the same total length.A theoretical approach forthe treatment of this general problem formsthe subject of the present paper.A fundamental role is played by theprobability of reaching the globalminimum, whose asymptoticalbehavior allows to provide useful information onthe efficiency ofrepeated trials.The second part of this work is devoted toa detailed analysis of threeoptimization algorithms whose evolution isindependent of the costfunction to be minimized: pure random search, grid search and randomwalk. These three examples give an interesting validationof thetheoretical results and provide a general procedure which can beemployed in the study of more complex optimization problems.     

Upper and Lower Semicontinuity for Set-Valued Mappings Involving Constraints

In vector optimization, several authors have studied the upper and lower semicontinuity for mappings involving constraints in topological vector spaces partially ordered through a cone with nonempty interior. In this paper, we give conditions about the upper and lower semicontinuity in the case that the ordering cone in the parameter space has possibly empty interior, as it happens in many function spaces and seqence spaces.