Essential Oil Analysis and Antimicrobial Evaluation of Three Aromatic Plant Species Growing in Saudi Arabia.

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 ß-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.

Evaluation of Antimicrobial Activity of Triphala Constituents and Nanoformulation.

The prevalence of nosocomial infections due to multidrug resistant (MDR) bacterial strains is associated with high morbidity and mortality. Folk medicine and ethnopharmacological data can provide a broad range of plants with promising antimicrobial activity. Triphala, an Ayurvedic formula composed of three different plants: Terminalia chebula Retz., Terminalia bellirica (Gaertn.) Roxb. (Combretaceae), and Phyllanthus emblica L. (Phyllanthaceae), is used widely for various microbial infections. Various extraction techniques were applied in the extraction of the biologically active constituents of Triphala in order to compare their efficiency. Microwave-assisted extraction (MAE) was shown to be the most efficient method based on yield, extraction time, and selectivity. The Triphala hydroalcoholic extract (TAE) has been chemically characterized with spectroscopic and chromatographic techniques. Triphala hydroalcoholic extract was evaluated alone or with carvacrol. Different drug formulations including cream and nanoemulsion hydrogel were prepared to assess the antimicrobial activity against selected microorganism strains including Gram-positive and Gram-negative bacteria and fungi. We used a lipophilic oil of carvacrol (5 mg/mL) and a hydrophilic TAE (5 mg/mL) ingredient in a dosage form. Two solutions were created: hydrogel containing nanoemulsion as a lipophilic vector dispersed in the gel as a hydrophilic vehicle and a cream formulation, an oil-in-water emulsion. In both cases, the concentration was 250 mg of active ingredient in 50 mL of final formulation. The formulas developed were stable from a physical and chemical perspective. In the nanoemulsion hydrogel, the oil droplet size ranged from 124 to 129 nm, with low polydispersity index (PdI) 0.132 ± 0.013 and negative zeta potential -46.4 ± 4.3 mV. For the cream, the consistency factor (cetyl alcohol and white wax) induced immobilization of the matrix structure and the stability. Triphala hydroalcoholic extract in drug nanoformulation illustrated might be an adjuvant antimicrobial agent for treating various microbial infections.

Preparation and biological evaluation of metronidazole derivatives with monoterpenes and eugenol.

Two series of metronidazole derivatives (ester derivatives and ether derivatives) were prepared reacting metronidazole and its acetic acid oxidized form with menthol, thymol, carvacrol, and eugenol. Both series of compounds were tested in vitro against two strains of Helicobacter pylori (the ATCC 26695 and P12), and one strain of Clostridium (Clostridium perfringens). Most of the prepared compounds showed biological activity against the targeted bacteria. Compound 11 was highly active against all tested bacterial strains, especially against P12 with IC50 0.0011 µM/ml. Compound 6 was highly active against C. perfringens with MIC 0.0094 nM/ml. Viability test was conducted for compound 11 to test its selectivity for normal human fetal lung fibroblasts (MRC5), and it was found to be non-toxic with IC50 more than 50 µM/ml.