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Background: Infectious diseases are responsible for millions of deaths a year worldwide. Antibiotics, which have saved so many lives and improved life expectancy, may become ineffective due to a worrying increase in bacterial resistance. Some of the appropriate actions that could be initiated to address this problem are to develop and search for new antimicrobial substances from medicinal plants, and combine antibiotics with antimicrobials agents isolated from a reservoir of bioactive natural products. Objectives: The purpose of this work was to study the chemical composition of the essential oil and hydrosol extract of Plumbago europaea, to evaluate their in-vitro antimicrobial activities and evaluate in-vitro combinatory antimicrobial effect of hydrosol extract with Gentamicin and Amphotericin B against a large panel of microorganisms in an effort to reduce their minimum effective dose and minimizing their side effects. Methods: The essential oil and hydrosol extract obtained from roots of Plumbago europaea were analyzed by GC/MS and tested for their antibacterial and antifungal activities against twelve different strains of microorganisms. The effectiveness, in-vitro, of the association between the hydrosol extract and both Gentamicin and Amphotericin B was also investigated using the checkerboard method. Results: The obtained results revealed that nine and four components, representing for 92.4 % and 97.4% of the total essential oil and hydrosol extract composition were identified, respectively and hydrosol extract was more active than the essential oil against all screened microorganisms, with interesting MIC values (19 μg/mL). An important effect of hydrosol extract was obtained in decreasing the MIC of Gentamicin and Amphotericin B in all tested combinations. Conclusion: The in-vitro combination of the hydrosol extract with Gentamicin and Amphotericin B led to substantial MIC reduction against all tested microorganisms. This combination can help to reduce the minimum effective dose of antimicrobial drugs used, which may help to decrease their side effects; and deliver these medicines with similar potency.

Background: Rhus pentaphylla Desf. (Anacardiaceae) widely grown in Algeria, is an underutilized plant and remains poorly studied. To investigate for the first time, the chemical composition profile of essential oil and hydrosol extract; besides Total Phenolic (TPC), Flavonoid (TFC) and Condensed Tannins Contents (CTC) of fruits, leaves and roots, the fatty acid composition was assessed. The radical scavenging activity of R. pentaphylla extracts was then evaluated. Methods: Essential oil and hydrosol extract were isolated respectively by hydrodistillation and liquidliquid- extraction from the aerial parts of R. pentaphylla. The antioxidant activity was evaluated using 2,2-Diphenyl-1-Picrylhydrazyl (DPPH) radical and ferric reducing antioxidant power (FRAP). Chemical compositions of various extracts were investigated using Gas Chromatography (GC) and GC-Mass Spectrometry (GC-MS). Results: The results of GC and GC-MS analysis revealed 83 components in essential oil and 75 components in hydrosol extract representing respectively 96.9% and 92.5% of the total extract composition. The main constituents were hexadecanoic acid (31.5%) followed by spathulenol (14.9%) in the oil while the higher amount present in the hydrosol extract was of spathulenol (14.2%). Otherwise, 13 and 18 fatty acids were identified in roots and fruits respectively. The highest levels of TPC and CTC were found in roots extracts while the highest quantity of TFC has been recorded in the leaves extract. Besides, hydrosol extract was able to scavenge DPPH and FRAP free radicals more efficiently than essential oil. Conclusion: R. pentaphylla contains bioactive substances that could be used as a new promising source of antioxidant compounds in different applications.

International audience; Campylobacter is one of the major causes of bacterial gastroenteritis worldwide. Humans are infected by eating contaminated meat and antibacterial activity of essential oils could be one of the solutions to reduce the contamination of animals. Here, we studied the antibacterial activity of the Daucus carota essential oil and its active molecules against Campylobacter and other Gram-negative bacteria. Chemically synthesized molecules including (E)methylisoeugenol, elemicin and eugenol were also studied. The results showed that the entire oil and the (E)-methylisoeugenol which is the more active molecule had a bactericidal effect. 2 Same effects were observed using purified and chemically synthesized molecules. In addition, the intracellular potassium and intracellular ATP contents were affected in Campylobacter cells treated with Daucus carota essential oil and its active molecules. Inhibition of the membrane bound F O F 1-ATPase was also observed. Finally, an efflux mechanism of the Daucus carota essential oil active molecules was described for the first time in gamma proteobacteria and the specific antibacterial activity against Campylobacter jejuni was correlated with the lack of this efflux mechanism in this species.