Screening of antimicrobial and insecticidal properties of essential oils extracted from three Tunisian aromatic and medicinal plants.

The essential oils (EOs) of Coriandrum sativum, Carum carvi and Artemisia herba-alba have been screened for their insecticidal activity against Tribolium castaneum, Sitophilus oryzae and Lasioderma serricorne and for their antimicrobial activity against Gram (+), Gram (-) bacteria and against yeast strain. Artemisia herba-alba EO showed good insecticidal activity with 24-h against L. serricorne (LC50 = 29.7) and against T. castaneum (66.1 µg/mL) and antibacterial potentials against Staphyloccocus aureus (MIC = 0.125 mg/mL). The antimicrobial activities of C. carvi EO, rich in D-carvone (72.4%) and D-limonene (23.8%) were particularly remarkable, with LC50 of 27.9 µg/mL against L. serricorne. Similarly, coriander EO, with linalool (64.6%) as the major compound was selected for its antimicrobial activities (Candida albicans, MIC = 1 mg/mL). These findings demonstrated that the tested EOs could be used as a natural source of insecticidal and antimicrobial activity, which may have a variety of uses in the food and pharmaceutical sectors.

Antioxidant, antibacterial and insecticidal activities of cypress (Cupressus sempervirens L.) essential oil.

The aerial parts of cypress (Cupressus sempervirens L.) of three collect regions (Bizerte, Ben-Arous and Nabeul) were reported for their essential oil (EO) compositions, antioxidant, antimicrobial and insecticidal activities. Results showed that the higher EO yields were observed in Bizerte and Ben Arous (0.56%), followed by Nabeul (0.49%). The EO composition showed the predominance of α-pinene with 36.72% in Bizerte, 30.22% in Nabeul and 30% in Ben-Arous. Cypress EO of Bizerte showed higher antiradical capacity (IC50 = 55 µg/mL) than Ben-Arous (IC50 = 97.50 µg/mL) and Nabeul (IC50 = 155 µg/mL). E. faecalis was the most sensitive strain to cypress EO of Bizerte with the largest inhibition zone (IZ = 65 mm). Regarding the insecticidal activity, cypress EO of Bizerte had the highest mortality of Tribolium castaneum with a lethal concentration of LC50 = 164.3 µL/L air after 24 h exposure.

Laurel essential oil: biological activities and application for semolina preservation against the red flour beetle Tribolium castaneum (Tenebrionidae).

The phytochemical composition of Laurus nobilis essential oil and their anticholinesterase, antioxidant, and insecticidal potential were studied. Also, the oil volatile fraction was compared in semolina at the beginning and after storage periods. For that, a headspace solid-phase-microextraction analysis (HS-SPME) coupled with gas chromatography and mass spectrometry was undertaken. Significant quantitative and qualitative differences of the oil volatile fraction were detected according to storage periods and occupation space ratios. Additionally, anti-acetylcholinesterase activity of L. nobilis oil against T. castaneum adults was evaluated. Results revealed that insecticide activity varied according to storage duration and occupation space. Besides, the oil acts on acetylcholine hydrolysis by inhibiting the activity of acetylcholinesterase. These results highlighted that L. nobilis essential oil may be recommended as an eco-friendly alternative for preserving semolina during storage.

Insecticidal effects of two Tunisian diatomaceous earth loaded with Thymus capitatus (L.) Hoffmans and Links as an ecofriendly approach for stored coleopteran pest control.

This study investigated composition and toxicity of Thyme EOs against two main stored grain insect pests. Carvacrol was distinguished as a major compound (78.34%). In laboratory tests, EOs applied by both direct contact and fumigant tests was more toxic to L. serricorne than T. castaneum. The EOs were also tested combined with two Tunisian Diatomaceous earths (DEs) against T. castaneum. The LC50 was 6.28 µL/L air for natural preparation EO/R1, 5.90 µL/L air for EO/R2 and 121.17 for crude EOs by fumigant test, respectively. While, contact test revealed that natural DEs; dust act as an insecticide with 'LC50' values of 3.22 and 0.29 µL/cm2f or R1 and R2, respectively. Moreover, a significant difference was noted between crude EO, EO/R1 and EO/R2. Overall, the enhancement of the Tunisian DEs' insecticidal activity by its mix with EOs may be a promising active substance as a stored grain protectant.

Fumigant toxicity of four essential oils against the carob moth Ectomyelois ceratoniae Zeller and the Mediterranean flour moth Ephestia kuehniella.

Eucalyptus leucoxylon, Rosmarinus officinalis, berries, and leaves of Schinus molle essential oils were analysed using GC-MS techniques and assessed for their fumigant toxicity against adults, larvae, and eggs of Ectomyelois ceratoniae and Ephestia kuehniella. Results showed that E. leucoxylon contained Spathulenol, p-Cymene, and Cryptone as major compounds. GC - MS analyses showed that the major compounds of R. officinalis essential oil were 1,8-Cineole, Camphor, and α-pinene. I-Phellandrene, t-Muurolol, and Phellandrene were the major components of the S. molle leaves; while I-Phellandrene, Limonen, and δ-Cadinene were the major components of the S. molle berries. S. molle berries were the most efficient followed by R. officinalis against E. ceratoniae and E. kuehniella. The most effective tested essential oil against E. ceratoniae larvae was S. molle berries. Results on the ovicidal and larvicidal effects of the tested oils demonstrated that R. officinalis was the most effective essential oil against E. kuehniella eggs.

Phenolic constitutents, antioxidant and repellent activities of coriander (Coriandrum sativum L.) fruits using different solvent extracts.

The organic solvent extracts (hexane, chloroform, acetone, methanol and water) of coriander fruits were reported for their antioxidant and repellent activities. The methanol and acetone extracts revealed the highest antiradical activity as compared to the other solvent extracts. HPLC analysis revealed that phenolic acids were the major compounds in chloroform and acetone extracts, whereas flavonoids in methanol and water extracts. The methanol extract of coriander fruits exhibited the highest repellent effect against coleopteran insects. Additionally, the hexane extract of coriander fruits also exhibited potent repellent and toxic activities against rice weevil. It appeared that coriander fruit extract obtained with the apolar solvent had more repellent potential against Sitophilus oryzae as compared to Tribolium castaneum. For Lasioderma serricorne, the methanol extract of coriander fruits reduced in a very significant way the adults followed by the chloroform and hexane extracts.

Phenological stage effect on phenolic composition and repellent potential of Mentha pulegium against Tribolium castaneum and Lasioderma serricorne

Objective: To elucidate for the first time the phenological stage effect on polyphenol,flavonoid and proanthocyanidin contents of pennyroyal (Mentha pulegium) as well as their antioxidant capacities and insecticidal potentials against Tribolium castaneum and Lasioderma serricorne. Methods: Crude methanol extracts from pennyroyal (Mentha pulegium) aerial parts were evaluated for their antiradical, reducing power activities and repellent potentials against selected coleopteran insects during different phenological stages. Results: Phenolic contents of pennyroyal aerial parts and their antioxidant effects were significantly dependent on maturity stage of the plant. The maximum of phenol production was reached during the full flowering stage. Apigenin was the major phenol in Mentha pulegium with an amount of 6.01 mg/g of dry vegetable matter during this period. Nevertheless, at fructification stage,the highest antioxidant activity was not related to high phenolic content. The repulsive effect of pennyroyal extract showed that Lasioderma serricorne was more susceptible to pennyroyal extract than Tribolium castaneum with corresponding median repellent dose values of 0.124and 0.006 mg/mL respectively. Moreover, great differences in insect repulsion depending on extract concentrations, exposure time and developmental stage was observed. For the lowest concentration (0.125 mg/mL), the repellent effect against Tribolium reached its maximum (90％)during the fructification stage (after 24 h of exposure) while this repellent effect was 80％during the vegetative stage. Conclusions: Due to the strong insecticidal potential of pennyroyal extracts, this study highlights the therapeutic properties of this plant and encourages its use as a safer, environmental-friendly and efficient insecticide in food industry.

Essential oil composition and anti Acanthamoeba studies of Teucrium ramosissimum.

The aim of the present study was to evaluate the chemical composition of the essential oil obtained from the aerial parts of T. ramosissimum by hydrodistillation and to investigate their anti-Acanthamoeba activity. Identification and quantification were realized by gas chromatography-mass spectrometry (GC-MS) and gas chromatography with flame ionization detection by (GC-FID). Sixty-eight compounds representing 97.78% of the essential oil were identified, of which δ-cadinene (18.63%), δ-cadinol (18.70%), ß-eudesmol (12.13%), γ-gurjunene (4.34%) and 8-cedrene (3.99%) were the main compounds. This essential oil contained a complex mixture consisting mainly on sesquiterpenes (80.62%) and monoterpene fractions (14.34%). The findings of the anti-Acanthamoeba assay indicate that T. ramosissimum essential oil have a good activity with an IC50 = 25.73 ± 0.75 µg/mL.