Évaluation du pouvoir antimicrobien des huiles essentielles de sept plantes médicinales récoltées au Maroc

Extracts of Brocchia cinerea (Delile) Vis Exhibit In Vivo Wound Healing, Anti-Inflammatory and Analgesic Activities, and Other In Vitro Therapeutic Effects

The plant Brocchia cinerea (Delile) (B. cinerea) has many uses in traditional pharmacology. Aqueous (BCAE) and ethanolic extracts (BCEE) obtained from the aerial parts can be used as an alternative to some synthetic drugs. In vitro, DPPH, FRAP and TAC are three tests used to measure antioxidant efficacy. Antibacterial activities were determined against one Gram positive and two Gram negative strains of bacteria. The analgesic power was evaluated in vivo using the abdominal contortion model in mice, while carrageenan-induced edema in rats was the model chosen for the anti-inflammatory test; wound healing was evaluated in an experimental second degree burn model. The results of the phytochemical analysis showed that BCEE had the greatest content of polyphenols (21.06 mg AGE/g extract), flavonoids (10.43 mg QE/g extract) and tannins (24.05 mg TAE/g extract). HPLC-DAD reveals the high content of gallic acid, quercetin and caffeic acid in extracts. BCEE has a strong antiradical potency against DPPH (IC50 = 0.14 mg/mL) and a medium iron reducing activity (EC50 = 0.24 mg/mL), while BCAE inhibited the growth of the antibiotic resistant bacterium, P. aeruginosa (MIC = 10 mg/mL). BCAE also exhibited significant pharmacological effects and analgesic efficacy (55.81% inhibition 55.64% for the standard used) and the re-epithelialization of wounds, with 96.91% against 98.60% for the standard. These results confirm the validity of the traditional applications of this plant and its potential as a model to develop analogous drugs.

Characterization of Primary Action Mode of Eight Essential Oils and Evaluation of Their Antibacterial Effect against Extended-Spectrum β-Lactamase (ESBL)-Producing Escherichia coli Inoculated in Turkey Meat

The current study aims to evaluate the antimicrobial activity of eight essential oils (EOs) against multidrug-resistant Escherichia coli strains, producing extended-spectrum β-lactamase (ESBL) enzymes and isolated from foods. Disc-diffusion assay showed that the inhibition diameters generated by EOs varied significantly among the tested EOs and strains. In fact, EOs extracted from Thymus capitaus, Eucalyptus camaldulensis, Trachyspermum ammi and Mentha pulegium exerted an important antimicrobial effect against tested strains, with the diameters of inhibition zones varied between 20 and 27 mm. Moreover, minimal inhibition and bactericidal concentration (MIC and MBC) values demonstrated that T. capitatus EOs generate the most important inhibitory effect against E. coli strains, with MIC values ranging from 0.02 to 0.78%. Concerning the mode of action of T. capitatus EO, the obtained data showed that treatment with this EO at its MIC reduced the viability of E. coli strains, their tolerance to NaCl and promoted the loss of 260-nm-absorbing material. In addition, in the presence of T. capitatus EO, cells became disproportionately sensitive to subsequent autolysis. Moreover, the inhibitory effect of T. capitatus was evaluated against two E. coli strains, experimentally inoculated (10⁵ CFU/g) in minced turkey meat, in the presence of two different concentrations of EO (MIC and 2 × MIC), and stored for 15 days. In both samples, EO exerted a bacteriostatic effect in the presence of concentrations equal to MIC. Interestingly, at 2 × CMI concentration, the bactericidal activity was pronounced after 15 days of storage. Our results highlighted that the use of essential oils, specially of T. capitatus, to inhibit or prevent the growth of extended-spectrum β-lactamase (ESBL)-producing E. coli in food, may be a promising alternative to chemicals.

Chemical Composition Related to Antimicrobial Activity of Moroccan Nigella sativa L. Extracts and Isolated Fractions

Background

Nigella sativa L. (NS) is an aromatic and medicinal plant commonly used in Mediterranean cuisine. Its grains contain a large amount of fixed oil and have many therapeutic virtues and medicinal properties (antioxidant, antidiabetic, antimicrobial, and anticancer).

Aim

The aim of this work is to study the antimicrobial activity of Nigella sativa L. extracts and separated fractions on various pathogenic strains and to correlate that with its chemical composition.

Methods

Extracts from Moroccan Nigella sativa seeds were extracted using successive organic solvents, and their hexane and acetone extracts were separated by column chromatography. The chemical composition of extracts, fractions, and essential oil was determined by GC-MS and HPLC-DAD. Extracts and fractions were evaluated for antimicrobial activity through disk diffusion against Gram-positive bacteria (Staphylococcus aureus, Bacillus cereus, and Listeria innocua), Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and yeast (Candida pelliculosa) for 1 mg/mL concentration. Bacterial strains were followed to study their behaviors over time in different concentrations. The minimum inhibitory concentration of Nigella sativa essential oil was determined against Staphylococcus aureus, Bacillus cereus, Escherichia coli, and Candida albicans. Results and Conclusion. Although hexane extract was active against both types of bacteria (Gram+ and Gram−), some of its fractions were specifically active against only one type. Fraction (SH4) had the highest activity (15 mm inhibitory diameter). Acetone extract was nonactive but surprisingly resulted in specific active fractions, and the most interesting one was (SA7) that had an inhibitory diameter of 13 mm. This antibacterial effect was related to fatty acids (linoleic and palmitic acids) in (SH4) and 17 pentatriacontene in (SA7). Moreover, the antifungal activity of hexane fractions (10–13 mm) was higher than hexane extract (8 mm), but for acetone, it was the opposite. Acetone extract had a higher activity (18 mm) than its fractions (8–12 mm), except for (SA7) (19 mm). Those inhibitions were attributed to gallic acid, cysteine, and apigenin in acetone extract and cysteine with ascorbic acid in fraction (SA7). Antifungal activity of the essential oil was more pronounced than the antibacterial one. Indeed, determined MICs in the first case were on the microgram scale (MIC = 8 μg/mL, Candida albicans), while in the second case, they were on the milligram scale (MIC = 0.96 mg/mL for Staphylococcus aureus, 0.5 mg/mL for Bacillus cereus, and 0.68 mg/mL for Escherichia coli). This antifungal activity was attributed to three major compounds beta-cymene, alpha-thujene, origanene, and thymoquinone. Results of strains behavior over time at different concentrations of the fractions showed all the curves went through a maximum around 20 hours and had a delay of expression of 5 hours at the start. Taking all results into count, Nigella sativa L. extracts and/or derived principles could form promising antimicrobial agents for therapeutical and industrial uses.

Chemical Characterization and Antioxidant, Antimicrobial, and Insecticidal Properties of Essential Oil from Mentha pulegium L

The chemical composition and antibacterial, insecticidal, and antioxidant properties of the essential oil from Mentha pulegium L. (M. pulegium) growing in Morocco were investigated in this work. To achieve this goal, the oils were obtained by using hydrodistillation before being characterized by GC-MS. The antibacterial and antifungal activities were conducted against pathogenic strains using the disc diffusion and MICS bioassays. The insecticidal activity was carried out versus C. maculatus using contact and inhalation tests. The antioxidant activity was performed by using DPPH and total antioxidant capacity bioassays. The chemical analysis of the oil showed that 20 compounds were identified, which represented 98.91% of the total oil. In the oil, the main components detected were R-(+)-pulegone (76.35%), carvone (5.84%), dihydrocarvone (5.09%), and octanol-3 (2.25%). The essential oil has moderate-to-strong broad-spectrum antibacterial and antifungal properties; the results showed that B. subtilis was the most sensitive strain to M. pulegium oil, with the largest inhibition diameter (25 ± 0.33). For the antifungal activity, the results obtained indicated that Aspergillus niger was the most sensitive fungal strain to M. pulegium oil with an inhibition percentage up to 100%. Regarding the insecticidal activity, the inhalation test showed a high efficacy (100% mortality), and a lethal concentration of LC₅₀ = 1.41 + 0.48 μL/L air was obtained after 24 hours of exposure. Moreover, the contact test showed that a total reduction in fertility and emergence was obtained with a dose of 20 μL/mL of acetone. Regarding the antioxidant activity, the sample concentration necessary to inhibit 50% of HE radicals (IC₅₀) was 7.659 mg/mL (DPPH) and 583.066 57.05 mg EAA/g EO (TAC).

Proposals for Antimicrobial Testing Guidelines Applied on Ajowan and Spanish Lavender Essential Oils

To fight the rising resistance of microorganisms to antibiotics, a strategy followed by several researchers is to focus on natural compounds, such as essential oils, as a source of potent antibacterial compounds. These last decades, hundreds of original papers have been written about microbiological assays that prove the antibacterial activity of essential oils and their use in the medical field. But can we really compare all the data available in the literature when the raw material, the microbiological assays, and/or the strains are different from one article to another? This review will point out the differences and the inadequate practices found in published articles that tested 2 lesser-studied essential oils-Spanish lavender and the ajowan-by the broth dilution method against Staphylococcus aureus, a human pathogenic bacterium. Many pitfalls were found in the literature, for example, a variable chemical composition rarely underlined by the authors, unidentified strains or clinical strains used without a related antibiogram, a lack of quality controls, and the assertion of questionable positive results. At last, some general guidelines that should be followed by every scientific researcher will be discussed.

Determination of Mineral Composition and Phenolic Content and Investigation of Antioxidant, Antidiabetic, and Antibacterial Activities of Crocus sativus L. Aqueous Stigmas Extracts

The aim of this study is to investigate the in vitro antioxidant, antidiabetic, and antibacterial activities of Moroccan and Italian Crocus sativus (L.) stigmas extracts. The antioxidant activity was evaluated by DPPH radical scavenging assay, and the results showed that the Moroccan extract has a powerful antioxidant activity with an IC₅₀ of 0.32 ± 0.059 μg/mL compared to the Italian extract (IC₅₀ of 3.14 ± 0.021 μg/mL). Additionally, the antidiabetic activity was evaluated by using alpha-amylase and alpha-glucosidase inhibition assay, and both extracts showed significant antidiabetic activity. However, the antibacterial activity was evaluated by the disc diffusion method to determine the inhibitory diameters and microplate dilutions method to determine the minimum inhibitory concentration. Our findings revealed that both Moroccan and Italian extracts were more effective against Gram-positive than Gram-negative bacteria. From this study, we can conclude that the studied extracts of C. sativus are rich in natural compounds and could have a broad application in the pharmaceutical, food, and medical fields.