Antimicrobial Efficiency of Essential Oils from Traditional Medicinal Plants of Asir Region, Saudi Arabia, over Drug Resistant Isolates.

Antimicrobial resistance (AMR) is a recurring global problem, which constantly demands new antimicrobial compounds to challenge the resistance. It is well known that essential oils (EOs) have been known for biological activities including antimicrobial properties. In this study, EOs from seven aromatic plants of Asir region of southwestern Saudi Arabia were tested for their antimicrobial efficacy against four drug resistant pathogenic bacterial isolates (Staphylococcus aureus, Streptococcus pyogenes, Escherichia coli, and Streptococcus typhimurium) and one fungal isolate (Candida albicans). Chemical compositions of EOs were determined by gas chromatography-mass spectrometry (GC-MS). The results revealed that EOs from Mentha cervina, Ocimum basilicum, and Origanum vulgare proved most active against all isolates with inhibitory zone range between 17 and 45 mm. The lowest minimum inhibitory concentration (MIC) of 0.025mg/ml was observed for Staph. aureus and Streptococcus pyogenes with EO of Origanum vulgare. All the three EOs showed significant anticandida activity. The results related to EOs from Mentha cervina, Ocimum basilicum, and Origanum vulgare demonstrated significant antimicrobial efficacy against drug resistant microorganisms.

Investigation of Extracts from Tunisian Ethnomedicinal Plants as Antioxidants, Cytotoxins, and Antimicrobials.

OBJECTIVE: To determine the medicinal potential of various plants and their parts extracted with different solvents. METHODS: The total phenolic content of acetonitrile/water (60%-40%) (ACN/W) and aqueous (W) extract fractions was determined by high-performance liquid chromatography (HPLC), and terpenic compounds were detected by gas chromatography/mass spectrometry (GC/MS). Antioxidant activity of the samples was evaluated using 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay and ß-carotene bleaching method. Cell viability was investigated by thiazolyl blue tetrazolium bromide [3-(4,5-dimethylthiazol)-2-yl 2,5-diphenyltetrazolium bromide] (MTT) assay. The mechanisms involved in cytotoxic activity were investigated in a murine macrophage cell line (RAW 264.7) and cancer lines. RESULTS: Our findings show that 11 plant species exhibited biological activity. In addition, moderate antibacterial activity was reported against one or more of the tested bacterial strains at two concentrations: 300 µg and 3 mg/disc. Furthermore, our data reveal that among all plants investigated, some extract and hydrophobic fractions were potent scavengers of the DPPH radical (6.78 µg/mL < EC50 < 8.55 µg/mL). Taken together, our results show that Nerium oleander (NOACN/W) and Pituranthos tortuosus (PTACN/W) were highly cytotoxic against RAW 264.7 cells with IC80 values of 0.36, and 1.55 µg/mL, respectively. In contrast, murine macrophage cell lines had low growth and were significantly sensitive to water extracts of Thymus hirtus sp. algeriensis (THW), Lavandula multifida (LMW), and ACN/W extract of Erica multiflora (EMACN/W) at doses > 400, 47.20, and 116.74 µg/mL, respectively. The current work demonstrates that RAW 264.7 cell proliferation was inhibited by samples in a dose-dependent manner. CONCLUSION: Our findings, validated through free radical scavenging activity, agar diffusion assay, and cytotoxicity of essential oils towards cancer cells, show that ethnomedicinal plants used in this work have a novel application as a tumor suppressor.

Chemical Composition, Antioxidant and Antimicrobial Activities of Thymus capitata Essential Oil with Its Preservative Effect against Listeria monocytogenes Inoculated in Minced Beef Meat.

The chemical composition, antioxidant and antimicrobial activities, and the preservative effect of Thymus capitata essential oil against Listeria monocytogenes inoculated in minced beef meat were evaluated. The essential oil extracted was chemically analyzed by gas chromatography-mass spectrometry. Nineteen components were identified, of which carvacrol represented (88.89%) of the oil. The antioxidant activity was assessed in vitro by using both the DPPH and the ABTS assays. The findings showed that the essential oil exhibited high antioxidant activity, which was comparable to the reference standards (BHT and ascorbic acid) with IC50 values of 44.16 and 0.463 µ g/mL determined by the free-radical scavenging DPPH and ABTS assays, respectively. Furthermore, the essential oil was evaluated for its antimicrobial activity using disc agar diffusion and microdilution methods. The results demonstrated that the zone of inhibition varied from moderate to strong (15-80 mm) and the minimum inhibition concentration values ranged from 0.32 to 20 mg/mL. In addition, essential oil evaluated in vivo against Listeria monocytogenes showed clear and strong inhibitory effect. The application of 0.25 or 1% (v/w) essential oil of T. capitata to minced beef significantly reduced the L. monocytogenes population when compared to those of control samples (P-value <0.01).