Cymbopogon giganteus Chiov. essential oil: Direct effects or activity in combination with antibiotics against multi-drug resistant bacteria

The discovery of new antimicrobial agents is necessary due to the emergence of multi-drug bacterial resistance. The aim of this work was to study the direct and indirect antimicrobial activity of a Beninese sample of Cymbopogon giganteus essential oil (EOCG) on multi-drug resistant clinical bacteria, its chemical composition, and its cytotoxicity. Direct antimicrobial activity was tested by determination of minimal inhibitory concentration (MIC), and indirect activity, by determining Fractional Inhibitory Concentration Index using checkerboard [fractional inhibitory concentration indices (FICI); synergy: FICI ≤ 0.5; additivity: 0.5 < FICI ≤ 1]. EOCG composition was determined by GC -MS and GC-FID and cytotoxicity was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphényltetrazolium bromide (MTT) assay. p-Menthane derivatives (54.87%) and limonene (12.07%) were detected as major compounds by GC analysis. Our results confirmed the direct antimicrobial activity of EOCG, but here on clinical resistant strains (MIC from 0.125% v/v to 0.5% v/v). We also show synergistic effects between EOCG and amoxicillin with FICI ranges of 0.12– 0.5 against two Escherichia coli resistant clinical strains, synergistic to additive effects between EOCG and colistin or oxacillin/ampicillin, respectively, against Pseudomonas aeruginosa PA544 and Staphylococcus epidermidis SECN361 (two resistant clinical isolates). Our results also indicate that EOCG had low cytotoxicity (IC50: 67.06 ± 2.694 μg/ml)

Antimicrobial potentials of essential oils extracted from West African aromatic plants on common skin infections

During the last decade, the advent of multi-drug resistant pathogens responsible for skin infections tends to make conventional treatments obsolete. Even though many studies have reported the antimicrobial properties of essential oils (EOs), the inconsistent use of various susceptibility testing methods has made information on antimicrobial potential of many EO varieties fragmentary. Using a single method approach, the objective of this work was to assess and to compare the antibacterial and antifungal properties, against skin pathogens, of EOs extracted from West African aromatic plants. Twenty-three plant samples collected in Benin and Burkina Faso were screened against 20 bacterial and fungal isolates obtained from skin lesions. Activity was evaluated by the determination of minimal inhibitory concentrations (MICs), with readings facilitated by the use of resazurin, a blue dye metabolized into pink resorufin by viable cells. Following this screening, nine EOs were found particularly active with MICs lower than 0.35% v/v. Gas Chromatography-Mass Spectrometry (GC/MS) analysis was used to determine the phytochemical profile of these active EOs which were found exceptionally rich in oxygenated monoterpenes, especially aldehydes, alcohols or phenols and their derivatives. Through this study, we demonstrated that several West African EOs have a significant antimicrobial potential which could, however, be considerably impacted by plant growing or harvesting place due to phytochemical composition variation. These EOs, even if their antimicrobial effects appeared lower than those of conventional antibiotics, constitute easily available mixtures of active compounds and could nevertheless be considered, in the context of increasing multidrug resistance, as complementary or alternative therapies in common skin infections management

In Vitro and In Vivo Toxicity Studies on Cymbopogon giganteus Chiov. Leaves Essential Oil From Benin

Cymbopogon giganteus Chiov. (Poaceae) is a medicinal plant used to treat various diseases in traditional medicine in several African countries. The present study aims to evaluate the oral and inhalation toxicity as well as the mutagenic effects of the essential oil of leaves (EOCG) from a sample collected in Benin. Mutagenic potential was assessed by the Ames test using strains TA98 and TA100. Oral acute toxicity was carried out by administration of a single dose of 2000 mg/kg b.w. to Wistar rats while oral subacute toxicity was assessed by daily administration of 50 and 500 mg/kg of EOCG for 28 days. Finally, inhalation toxicity was assessed by administration of a single dose of 0.125%, 0.5%, 2% or 5% v/v of EOCG emulsions in 0.05% v/v lecithin solution in sterile water for the first experiment, and in a second one by administration of single dose of 0.125% or 0.5% v/v. A broncho-alveolar lavage was performed after 3 h or 24 h, respectively. The results show that EOCG is not mutagenic on strains at the highest concentration tested (200 g/plate). In the acute oral toxicity study, EOCG induce neither mortality nor toxicity, showing that the LD is greater than 2000 mg/kg. The subacute oral toxicity study at both doses did not show any significant difference in body weight, relative organ weight, hematological and/or biochemical parameters or histopathology as compared to the control group. EOCG induced mortality and inflammation in lungs 3 h after administration of a single dose of 5% or 2% v/v. Single doses of 0.125% or 0.5% v/v did not induce inflammation, cell recruitment nor cytotoxicity in lungs 3 h or 24 h after administration, suggesting safety at these concentrations. This first report on the toxicity will be useful to guide safe uses of EOCG