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Arabian flora is a rich source of bioactive compounds. In this study, we investigated three aromatic plant species with the aim of finding valuable sources of antimicrobial agents against common pathogenic microorganisms. We focused especially on microorganisms, which cause outbreaks of infectious disease during mass gatherings and pilgrimages season in Saudi Arabia. The essential oils of three aromatic plant species were hydrodistilled from flowering aerial parts of Lavandula pubescens Decne. and Pulicaria incisa subsp. candolleana E.Gamal-Eldin, and from leaves, stems, ripe and unripe fruits of Juniperus procera Hochst. Ex Endl. They were subsequently analyzed by gas chromatography-mass spectrometry (GC-MS). The main constituents of L. pubescens were found to be carvacrol (55.7%), methyl carvacrol (13.4%), and β-bisabolene (9.1%). P. incisa subsp. Candolleana essential oil was rich in linalool (33.0%), chrysanthenone (10.3%), eugenol (8.9%), and cis-chrysanthenol (8.0%), the major components of J. procera essential oil were α-pinene (31.3–62.5%) and δ-3-carene (7.3–30.3%). These essential oils were tested against thirteen American Type Culture Collection (ATCC) strains of Gram-positive and Gram-negative bacteria using the agar diffusion assay. The only effective essential oil was that of L. pubescens and the most sensitive strains were Acinetobacter baumannii, Salmonella typhimurium, Shigella sonnei, Enterococcus faecalis and Staphylococcus epidermidis. Carvacrol, the major constituent of L. pubescens, was tested on these strains and was compared with vancomycin, amikacin, and ciprofloxacin. The Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) assays of L. pubescens essential oil and carvacrol revealed that Gram-negative strains were more susceptible than the Gram-positive ones.

The present study describes the antioxidant and antimicrobial activities of the essential oil of Pulicaria incisa (Lam.), obtained from the aerial part harvested from Oulad Embarek (Beni Mellal-Khenifra region located in the center in Morocco). The P. incisa essential oil presents IC50 using DPPH of 105.99 ± 4.25 μg/mL and an EC50 using FRAP of 87.21 ± 3.1 μg/mL. The antimicrobial activity of the oil was evaluated for five microorganisms. The results obtained revealed different degrees of sensitivity of the bacterial strains tested. The Allorhizobium vitis (S4) and Agrobacterium tumefaciens( C58) strains are the most sensitive to the investigated oil, with inhibition diameters greater than 20 mm and a MIC and CMB of 0.25 (v/v) and 0.5 (v/v) respectively.

In this study, 15 bacterial endophytes linked with the leaves of the native medicinal plant Pulicaria incisa were isolated and identified as Agrobacterium fabrum, Acinetobacter radioresistant, Brevibacillus brevis, Bacillus cereus, Bacillus subtilis, Paenibacillus barengoltzii, and Burkholderia cepacia. These isolates exhibited variant tolerances to salt stress and showed high efficacy in indole-3-acetic acid (IAA) production in the absence/presence of tryptophan. The maximum productivity of IAA was recorded for B. cereus BI-8 and B. subtilis BI-10 with values of 117 &plusmn, 6 and 108 &plusmn, 4.6 &mu, g mL&minus, 1, respectively, in the presence of 5 mg mL&minus, 1 tryptophan after 10 days. These two isolates had a high potential in phosphate solubilization and ammonia production, and they showed enzymatic activities for amylase, protease, xylanase, cellulase, chitinase, and catalase. In vitro antagonistic investigation showed their high efficacy against the three phytopathogens Fusarium oxysporum, Alternaria alternata, and Pythium ultimum, with inhibition percentages ranging from 20% &plusmn, 0.2% to 52.6% &plusmn, 0.2% (p &le, 0.05). Therefore, these two endophytic bacteria were used as bio-inoculants for maize seeds, and the results showed that bacterial inoculations significantly increased the root length as well as the fresh and dry weights of the roots compared to the control plants. The Zea mays plant inoculated with the two endophytic strains BI-8 and BI-10 significantly improved (p &le, 0.05) the growth performance as well as the nutrient uptake compared with an un-inoculated plant.

Activated microglial cells release various mediators, which cause neuronal cell death and have been implicated in different neurological disorders. The present study demonstrates that an infusion prepared from the plant Pulicaria incisa ( Pi ) inhibits microglial activation and down-regulates levels of the inflammatory cytokines interleukin (IL)-1β, IL-6, and of the toxic mediators nitric oxide and glutamate. The infusion was also shown to have antioxidant properties in cell-free assays (e.g., differential pulse voltammetry) and in a cellular assay, in which the infusion attenuated the induced accumulation of intracellular reactive oxygen species (ROS). We found that Pi infusion is rich in polyphenols, especially chlorogenic acids and ferulic acids, which might be responsible for the observed activities. It is proposed that Pi infusion be further evaluated for use as a functional beverage for the prevention and/or treatment of chronic diseases, especially neurodegenerative disorders in which microglial activation and oxidative stress play important roles.

In recent years, antimicrobial activities of essential oils have been intensively explored, mainly in researching and developing new antimicrobial agents to overcome microbial resistance. The present study investigates the chemical composition and antimicrobial activities of essential oils obtained from two Asteraceae: Asteriscus graveolens (Forssk.) Less. and Pulicaria incisa (Lam.) DC. Chemical analysis was performed using a combination of capillary GC-FID and GC/MS analytical techniques. The major component of Asteriscus graveolens were cis-chrysanthenyl acetate (31.1%), myrtenyl acetate (15.1%), and kessane (11.5%), while for Pulicaria incisa the main components were chrysanthenone (45.3%) and 2,6-dimethylphenol (12.6%). The oils obtained from the aerial parts were tested against sixteen microbial strains by agar well diffusion technique and dilution methods and showed minimum inhibitory concentrations (MIC) in the range of 19 - 1250 μg/ml. A good antibacterial activity against a common nosocomial pathogen, Acinetobacter baumanniiATCC 19606 was observed, especially from Pulicaria incisa essential oil, with a MIC value up to 19 μg/ml. These results give significant information about the pharmacological activity of these essential oils, which suggest their benefits to human health, having the potential to be used for medical purposes.