Comparative evaluation of antioxidant and insecticidal properties of essential oils from five Moroccan aromatic herbs

This study describes the antioxidant and insecticidal activities of essential oils (EOs) of Mentha suaveolens subsp. timija, Thymus satureioides, Achillea ageratum, Cotula cinerea and Salvia officinalis widely used in Morocco as flavorings, food additives and preservatives. Sixty seven components were identified accounting for more than 95.0% of the total oils. M. suaveolens subsp. timija oil had as main components menthone and pulegone. A. ageratum oil was particularly rich in artemisyl acetate and yomogi alcohol. The essential oil of T. satureioides was characterized by high contents of carvacrol and borneol. C. cinerea oil contained trans-thujone and cis-verbenyl acetate as major constituents, whereas S. officinalis oil was characterized by trans-thujone and camphor. Antioxidant activities were examined by means of 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), reducing power, β-carotene/linoleic acid bleaching and ABTS radical tests. In all assays, the highest antioxidant potency was observed in T. satureioides EO with IC50 values ranging from 0.15 ± 0.36 μg mL-1 to 0.23 ± 0.67 μg mL−1 across the four assays. The in vitro evaluation of the insecticidal activity showed that M. suaveolens subsp. timija EO present the highest insecticidal efficiency against adults of Tribolium castaneum with LD50 and LD90 values of 0.17 μL cm−2 and 0.26 μL cm−2, respectively and LT50, LT90 values ranged from 44.19 h to 2.98 h and 98.14 h to 6.02 h, respectively. Our data support the possible use of T. satureioides oil as potential antioxidant agent, while M. suaveolens subsp. timija oil can be developed as a new natural bio-insecticide

Synergistic effects of three Moroccan thyme essential oils with antibiotic cefixime

The association of essential oils (EOs) with antibiotics provides a promising solution towards combating resistant bacteria. Thus, the aim of this study was to examine for the first time the possible synergistic interaction between EOs of three Moroccan thymes, namely Thymus leptobotrys (carvacrol [79.1%]), Thymus pallidus (γ-terpinene [29.6%], thymol [26.8%] and p-cymene [18.9%]) and Thymus ciliatus (carvacrol [26.2%], p-cymene [19.6%], thymol [17.3%] and γ-terpinene [14.6%]) and the antibiotic cefixime against selected pathogenic bacteria. The results showed that all thyme EOs presented interesting antibacterial potency and important synergistic effects with cefixime. Thymus leptobotrys EO showed the strongest efficacy against all tested bacteria (minimum inhibitory concentration values 0.14 mg/mL to 73.92 mg/mL), and the best synergistic effect (fractional inhibitor concentration indices: 0.26 to 0.5; gain: 4- to 130-fold). This synergistic interaction between the studied thyme EOs and cefixime may provide a basis for future applications for the control of antibiotic-resistant bacteria

Essential oil composition and antimicrobial activity of wild and cultivated mint timija (Mentha suaveolens subsp. timija (Briq.) Harley), an endemic and threatened medicinal species in Morocco

The hydro-distilled essential oils obtained from aerial parts of the wild (w) and cultivated (c) mint timija (Mentha suaveolens subsp. timija), an endemic medicinal species of Morocco, have been analyzed by GC–MS and screened for antimicrobial activity. In total, 35 compounds representing more than 98% of the oils were identified. Menthone (39.4(w)–10.8(c)%), pulegone (62.3(c)–34.3(w)%) and isomenthone (9.3(c)–7.8(w)%) were found as the main components for the two oils. The volatiles of the wild and cultivated material differed significantly in both the percentage of the main components and antimicrobial effect. Pulegone was more dominant in cultivated mint timija (62.3%) than in wild one (34.3%), while menthone was more abundant in the wild material (39.4%). In the antimicrobial assays, both oils displayed good to excellent activity against all microorganisms tested with the oil of the cultivated form being more active

Effects of cultivation and application of inorganic fertilizer on volatile oils constituents and biological properties of Thymus leptobotrys Murb. and T. maroccanus Ball. from Morocco

Thymus leptobotrys and T. maroccanus are endemic Moroccan medicinal species that are intensively exploited from the wild because of their wide ranging therapeutic properties. In order to preserve these valuable medicinal plants from risk of extinction, the cultivation (with and without N, P, and K fertilizer) and its consequent effect on oil chemical composition and biological activities were studied. Carvacrol (64.1–78.1%) was found as the major constituent in oil samples, followed by p-cymene (4.7–12.4%) and γ-terpinene (3.2–7.9%). Cultivation without using N, P, and K fertilizer caused a slight decrease in carvacrol content against an increase of its main precursor p-cymene. However, application of N, P, and K fertilizer increased the carvacrol content of 3.9% for T. maroccanus and 9.4% for T. leptobotrys oils compared with unfertilized plants. Regarding the antioxidant activity, wild thyme oils showed the highest potency in all assays, while oils from cultivated plants fertilized with N, P, and K had greater activity than oils from plants not receiving fertilizer. Concerning the antimicrobial activity, oils from fertilized plants exhibited the highest inhibitory effect against most tested strains with MIC values ranged from 0.03 to 31.68 mg/mL. From this work, it can be concluded that cultivation could be a promising solution to ensure the sustainable utilization of these endemic and threatened medicinal thyme species

Chemical characterization and insecticidal properties of essential oils from different wild populations of Mentha suaveolens subsp. timija (BRIQ.) HARLEY from Morocco

The present study is the first investigation of the volatile-oil variability and insecticidal properties of the endemic Moroccan mint Mentha suaveolens subsp. timija (mint timija). The yield of essential oils (EOs) obtained from different wild mint timija populations ranged from 0.20±0.02 to 1.17±0.25% (v/w). GC/MS Analysis revealed the presence of 44 oil constituents, comprising 97.3-99.9% of the total oil compositions. The main constituents were found to be menthone (1.2-62.6%), pulegone (0.8-26.6%), cis-piperitone epoxide (2.9-25.5%), piperitone (0.3-35.5%), trans-piperitone epoxide (8.1-15.7%), piperitenone (0.2-9.6%), piperitenone oxide (0.5-28.6%), (E)-caryophyllene (1.5-11.0%), germacrene D (1.0-15.7%), isomenthone (0.3-7.7%), and borneol (0.2-7.3%). Hierarchical-cluster analysis allowed the classification of the EOs of the different mint timija populations into four main groups according to the contents of their major components. This variability within the species showed to be linked to the altitude variation of the mint timija growing sites. The results of the insecticidal tests showed that all samples exhibited interesting activity against adults of Tribolium castaneum, but with different degrees. The highest toxicity was observed for the EOs belonging to Group IV, which were rich in menthone and pulegone, with LC50 and LC90 values of 19.0-23.4 and 54.9-58.0 μl/l air in the fumigation assay and LC50 and LC90 values of 0.17-0.18 and 0.40-0.52 μl/cm2 in the contact assay

Antioxidative activity and synergistic effect of Thymus saturejoides Coss. essential oils with cefixime against selected food-borne bacteria

Thymus saturejoides is a perennial shrub widely distributed in the arid and semi arid parts of the Moroccan mountains. Essential oils (EOs) of this species are used extensively in food and pharmaceutical industries because of their wide biological and pharmacological properties. To our knowledge, no data are available on the antibacterial and antioxidant activities of T. saturejoides EOs in relation to the chemical variability of the species. Also, the potential synergistic interaction of EOs from this species as natural antimicrobial agent with conventional antibiotics against food-borne bacteria has not been investigated. Thus, the aim of the present study was to determine the volatile oil constituents of EOs from three wild Moroccan T. saturejoidespopulations collected from Northwest–Southeast of Morocco (June, 2011). Antioxidant activity and their antibacterial potency (singly and in combination with cefixime) against selected food-borne bacteria was then determined. Gas chromatography–mass spectrometry (GC–MS) analysis revealed 30 compounds, representing 98.6 to 99.5% of the total oils. The major constituents identified were carvacrol (45.3%), p-cymene (8.9%), linalool (8.4%), and borneol (7.5%) in oil from the Er-Rich population (arid site); carvacrol (26.5%), borneol (20.1%), camphene (8.0%), and γ-terpinene (5.6%) in oil from Ourika population (medium arid site) and carvacrol (25.3%), borneol (19.7%), camphene (7.6%), and p-cymene (6.6%) in oil from Taws population (less arid site). Essential oil obtained from Er-Rich population showed the highest antioxidant activity as measured by 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical scavenging ability, reductive potential, and β-carotene/linoleic acid assays with IC50 values of 44.54 ± 0.92 μg/mL, 22.90 ± 0.16 μg/mL and 19.17 ± 0.01 μg/mL, respectively. Antibacterial tests showed that the oils from this species had a high inhibitory activity against tested bacteria, with the exception of Pseudomonas aeruginosa. The most potent activity was observed with oil obtained from the Er-Rich population with minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) values of 0.14 to 0.55 mg/mL and 0.28 to 0.55 mg/mL, respectively. Out of 21 combinations tested between EOs and cefixime, 67% showed total synergism, 19% had partial synergistic interaction and 14% showed no effect. Oil from the Er-Rich population exhibited the highest synergistic effect with antibiotic (FIC index values of 0.29 to 0.5). The synergy displayed by this combination of EO and cefixime may be of potential benefit for control of food-related bacteria, consequently permitting the use of lower doses of standard antibiotics