Repellent, irritant and toxic effects of plant EO compounds on the malaria vector Anopheles gambiae ss Giles

yrethroids resistance has become widespread among malaria vector Anopheles gambiae populations in Africa. Alternative insecticides must be considered to prevent diseases transmission by An. gambiae bites. The long lasted treated bed nets are particularly efficient to prevent blood meals on humans and thus to reduce the risks of transmissions. Previous studies have identified plant essential oils (EO) as a potential alternative to pyrethroids. Four of them showed significant repellent, irritant and/or toxic effects against An. gambiae. The objective of this study was to evaluate the repellent, irritant and toxic actions of the major compounds of these four EO from citronella (Cymbopogon winterianus), cinnamon (Cinnamomum zeylanicum), cumin (Cuminum cyminum) and thyme (Thymus vulgaris), against females An. gambiae. We tested the spatial repellency, the contact irritancy and the toxicity effects of each product with laboratory tests over 180 females, for each action tested. The complete EO, the mixture of the major compounds (>3%) and the two currently used repellent (DEET) and insecticide (Permethrin) were also tested. The most promising compounds were similarly tested with two strains of An. gambiae: resistant to pyrethroids (KdrKis) and resistant to carbamates (AcerKis). At last assays in tunnels to simulate field conditions were made to determine their efficacy when a blood meal was offered. Carvacrol, geraniol, cuminaldehyde and cinnamaldehyde showed the best repellent and irritant effects among all products tested. Cuminaldehyde and cinnamaldehyde revealed to be more efficient against the resistant strains than the susceptible strain of An. gambiae, and with carvacrol, they were particularly efficient to inhibit blood meals in simulated field conditions. The study also showed interested characteristics of plant EO which led to new research directions to use plant EO for biological control. At last this study was the first to test the efficiency of DEET on resistant An. gambiae strains. (Résumé d'auteur

Calli Essential Oils Synergize with Lawsone against Multidrug Resistant Pathogens.

The fast development of multi-drug resistant (MDR) organisms increasingly threatens global health and well-being. Plant natural products have been known for centuries as alternative medicines that can possess pharmacological characteristics, including antimicrobial activities. The antimicrobial activities of essential oil (Calli oil) extracted from the Calligonum comosum plant by hydro-steam distillation was tested either alone or when combined with lawsone, a henna plant naphthoquinone, against MDR microbes. Lawsone showed significant antimicrobial activities against MDR pathogens in the range of 200-300 µg/mL. Furthermore, Calli oil showed significant antimicrobial activities against MDR bacteria in the range of 180-200 µg/mL, Candida at 220-240 µg/mL and spore-forming Rhizopus fungus at 250 µg/mL. Calli oil's inhibition effect on Rhizopus, the major cause of the lethal infection mucormycosis, stands for 72 h, followed by an extended irreversible white sporulation effect. The combination of Calli oil with lawsone enhanced the antimicrobial activities of each individual alone by at least three-fold, while incorporation of both natural products in a liposome reduced their toxicity by four- to eight-fold, while maintaining the augmented efficacy of the combination treatment. We map the antimicrobial activity of Calli oil to its major component, a benzaldehyde derivative. The findings from this study demonstrate that formulations containing essential oils have the potential in the future to overcome antimicrobial resistance

Repellent, irritant and toxic effects of essential oil constituents on Bemisia tabaci (Gennadius)

Whiteflies, Bemisia tabaci, are a widespread pest in agriculture, causing crop loss up to 100% by direct and indirect damage. Controlling this pest has proven difficult due to the fact that they stay underside the leaves and their ability to become resistant to conventional pesticides rapidly. Also, environmental and health concerns associated with the use of synthetic pesticides are rising. Therefore, new methods should be investigated to protect crops from B. tabaci. Insect proof nets (IPNs) create a physical barrier between the crop and a pest insect, but this alone is not suitable against small insects like B. tabaci. A possible solution is combining insect proof nets (IPN) with a naturally occurring repellent. Essential oils, mixtures of volatile secondary metabolites of plants, have been shown to have repellent and toxic abilities against many pest insects, including whiteflies. This study investigates the role of the different compounds in four essential oils; Cumin (Cuminum cyminum), Cinnamon (Cinnalonum zeylanicum), Lemongrass (Cymbopogon citratus) and Citronella grass (Cymbopogon winterianus), to see if the constituents are toxic, repellent or irritant. This is also used as a screening for compounds that seem promising to be used in combination with IPNs in the field. This should be a highly repellent, but not very toxic compound, to repel B. tabaci but with a reduced risk of the fast development of resistance. In this study I found that most constituents of essential oils have one dominant role (i.e. they are for example toxic or repellent but not both) and the effects of these different compounds combined add up in the mixture of the essential oil. As for the essential oil of citronella grass, this oil is less toxic than some of its individual compounds, suggesting interactions between the compounds when mixed. The most promising compounds to be used against B. tabaci in the field, based on their high repellency and low toxicity, are cinnamaldehyde (repellent at <0.084 mg/L and toxic at 8.4 mg/L) and linalool (repellent at 0.006 mg/L but with unknown toxicity). (Résumé d'auteur

Insecticide resistance modifies mosquito response to DEET and natural repellents

Background: Pyrethroid and organophosphate resistance in the malaria vector Anopheles gambiae has led to the search for not only alternative insecticides, but also repellent chemical compounds. However, little is known about the potential actions of repellents and the cross-resistance risk between insecticide and repellent compounds. Methods: Here we show the action of permethrin, DEET, geraniol, carvacrol, culminaldehyde and cinnamaldehyde against three A. gambiae strains: 'Kis' (Kisumu susceptible strain), 'KdrKis' (pyrethroid resistant strain) and 'AcerKis' (organophosphate resistant strain), the last two differing from the first by a mutation on the kdr and ace1 genes, respectively. Conclusions: Results from the DEET assays show it induced repellency for the resistant KdrKis and AcerKis strains but maintained irritancy for the susceptible strain. More generally, we show resistance genes modify the behavior of An. gambiae, increasing or decreasing the effectiveness of DEET and natural compounds, depending on the mutation. These findings offer a new avenue for research on the target and mechanism of repellent compounds. We discuss these findings in the context of vector control strategies

Chemical Composition and in Vitro Evaluation of the Antioxidant and Antimicrobial Activities of Eucalyptus gillii Essential Oil and Extracts

In this study, essential oil and various extracts (hexane, petroleum ether, acetone, ethanol, methanol and water) of Eucalyptus gilii were screened for their chemical composition, antimicrobial and antioxidant activities. The essential oil chemical composition was analyzed by gas chromatography-mass spectrometry (GC-MS) and gas chromatography-flame ionization detection (GC-FID), respectively. Thirty four compounds were identified, corresponding to 99.5% of the total essential oil. Tannins [104.9-251.3 g catechin equivalent (CE)/Kg dry mass], flavonoids [3.3-34.3 g quercetin equivalent (QE)/Kg dry mass], phenolics [4.7-216.6 g gallic acid equivalent (GAE)/Kg dry mass] and anthocyannins [1.2-45.3 mg cyanidin-3-glucoside equivalent (C3GE)/Kg dry mass] of various extracts were investigated. Free radical scavenging capacity of all samples was determinedt. In the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, the IC50 of essential oil was 163.5 ± 10.7 mg/L and in the 2,2'-azinobis-3-ethylbenzothiazoline-6-sulphonate (ABTS) assay, it was 94.7 ± 7.1 mg/L. Among the various extracts, the water extract showed the best result (IC50 = 11.4 ± 0.6 mg/L) in the DPPH assay which was comparable to vitamin C (IC50 = 4.4 ± 0.2 mg/L). The antimicrobial activities were evaluated against different bacterial and fungal strains. Gram positive bacteria were found to be more sensitive to the essential oil and extracts than Gram negative ones. Anthocyanins seem to have a major effect on the growth of Bacillus subtilis (R2 = 0.79). A significant antifungal activity was observed against the yeast and fungi. Correlations between chemical composition and antioxidant activities were studied and R2 values were about 0.96 for the effect of phenolics on the DPPH assay

Enantiomeric Ratio Changes of Terpenes in Essential Oils from Hybrid Eucalyptus grandis × E. tereticornis and its Pure Species

Some Eucalyptus species produce oils with biological activities and the effect of their interspecifc hybridization on the enantiomeric composition of terpenes has not been reported. The enantiomeric excesses of monoterpenes in the essential oil of Eucalyptus grandis × E. tereticornis and its parental taxa were determined by gas chromatography-mass spectrometry (GC-MS), and to resolve coelutions problems by preparative high performance liquid chromatography (HPLC)and GC-MS with two columns in series. The essential oil composition of the hybrid presented qualitative and quantitative differences with the composition of its parental taxa. Great differences were found for the enantiomeric ratio in monoterpene alcohols among the three essential oils. Our results suggest that the enantiomeric analysis can be a reliable method for the study of how theinterspecifc hybridization can module the enantiomeric chemical profle in Eucalyptus essential oils. These results suggest the use of interspecifc hybridization to improve or expand the source of bioactive compounds.Fil: Naspi, Cecilia Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Alvarez Costa, Agustin. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Lucia, Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Gonzalez Audino, Paola Andrea. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; ArgentinaFil: Masuh, Hector Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Unidad de Investigación y Desarrollo Estratégico para la Defensa. Ministerio de Defensa. Unidad de Investigación y Desarrollo Estratégico para la Defensa; Argentin

A Comparison Between the Effect of Cuminum Cyminum and Vitamin E on the Level of Leptin, Paraoxonase 1, HbA1c and Oxidized LDL in Diabetic Patients.

Diabetes is one of the most common metabolic diseases in the world. Vitamin E reduces protein glycation and improves insulin sensitivity, while cumin is effective in remission of diabetes. Therefore this study was designed to evaluate the effects of vitamin E and cumin essential oil, on the blood level of leptin,glycosylated hemoglobin (HbA1C) and also on lipid profile in diabetic patients.In this double blind clinical trial, 95 diabetic patients were selected and randomly dividedinto three groups.The first group received cumin essential oil in capsule form. The second group received Vitamin E, and the third group was used ascontrol receiving oral gelatin capsules as placebo for three months period.Blood glucose, lipid profile, apolipoprotein A1 (ApoA1), apolipoprotein B (ApoB), leptin, HbA1c, oxidized LDL (oxLDL), and paraoxonase1 activity were measured. The results showed reduction in oxLDL and significant increase in paraoxonase 1 in Vitamin E group by the end of the third month period (P<0.05). Cumin group showed decrease in blood glucose, HbA1C, triglyceride, leptin and ox-LDL. ApoA1 and paraoxonase1 were also increased by cumin treatment (P<0.05).Diabetic complications may have been reduced by intake of Vitamin E and cumin essential oil. Cumin in comparison with vitamin E has broader impact and it is more beneficial in terms of ability to reduce the diabetic index

Eucalyptus oleosa Essential Oils: Chemical Composition and Antimicrobial and Antioxidant Activities of the Oils from Different Plant Parts (Stems, Leaves, Flowers and Fruits)

Essential oils obtained by hydrodistillation from the different parts (stems, adult leaves, immature flowers and fruits) of Eucalyptus oleosa were screened for their antioxidant and antimicrobial properties and their chemical composition. According to GC-FID and GC-MS, the principal compound of the stem, immature flowers and the fruit oils was 1,8-cineole, representing 31.5%, 47.0% and 29.1%, respectively. Spathulenol (16.1%) and γ-eudesmol (15.0%) were the two principal compounds of adult leaves oil. In the DPPH (1,1-diphenyl-2-picrylhydrazyl) assay, the oils of the four parts showed moderate antioxidant activity. In the ABTS (2,2’-azinobis-3-ethylbenzothiazoline-6-sulphonate) assay, the most active part was the adult leaves, with a IC50 value 13.0 ± 0.6 mg/L, followed by stems (IC50 = 43.5 ± 1.4 mg/L). The essential oils showed a better antibacterial activity against Gram-positive and Gram-negative bacteria, and a significant antifungal activity also was observed against yeast-like fungi. A strong correlations between oxygenated monoterpenes and antimicrobial activity (especially 1,8-cineole) were noted (R2 = 0.99, 0.97 and 0.79 for B. subtilis, P. aeruginosa and C. albicans, respectively)