Sara M. Palacios

Efficacy of Essential Oils from Edible Plants as Insecticides Against the House Fly, Musca Domestica L.

The compositions of 12 essential oils (EOs) obtained by hydrodistillation of edible fruits and herbs were analyzed by gas chromatography/mass spectroscopy (GC/MS). The insecticidal activity of each oil against the house fly Musca domestica was evaluated by placing flies in a glass jar with a screw cap that held a piece of EO-treated cotton yarn. The dose necessary to kill 50% of flies (LC50) in 30 min was determined at 26 ± 1°C. Twelve EOs and 17 individual terpenes were assayed against M. domestica, showing LC50 values ranging from 3.9 to 85.2 and from 3.3 to >100 mg/dm3, respectively. EO from Citrus sinensis was the most potent insecticide (LC50 = 3.9 mg/dm3), followed by EOs from C. aurantium (LC50 = 4.8 mg/dm3) and Eucalyptus cinerea (LC50 = 5.5 mg/dm3). According to GC/MS analysis, limonene (92.47%), linalool (1.43%), and β-myrcene (0.88%) were the principal components of C. sinensis EO. Limonene was also the principal constituent (94.07%) of C. aurantium, while 1,8-cineole (56.86%) was the major constituent of E. cinerea EO. 1,8-Cineole was most active against M. domestica (LC50 = 3.3 mg/dm3), while (4R)(+)-limonene, was moderately active (LC50 = 6.2 mg/dm3). Dimethyl 2,2-dichlorovinyl phosphate (DDVP) selected as a positive control, showed an LC50 of 0.5 mg/dm3. EOs from C. sinensis, C. aurantium, and E. cinerea show promise as natural insecticides against houseflies.

Potent Limonoid Insect Antifeedant from Melia azedarach

Systematic fractionation of a fruit extract from Argentine Melia azedarach L., which was monitored by an insect antifeedant bioassay, led to the isolation of meliartenin, a limonoid antifeedant, which existed as a mixture of two interchangeable isomers. At 4 μg/cm2 and 1 μg/cm2, the isomeric mixture was as active as azadirachtin in strongly inhibiting the larval feeding of Epilachna paenulata Germ. (Coleoptera: Coccinellidae) and the polyphagous pest, Spodoptera eridania (Lepidoptera: Noctuidae), respectively.

Antifeedant activity of ethanolic extract from Flourensia oolepis and isolation of pinocembrin as its active principle compound

The ethanolic extract from Flourensia oolepis aerial parts showed strong antifeedant activity against the pest larvae, Epilachna paenulata, with an antifeedant index (AI%) of 99.1% at 100 microg/cm(2). Based on chromatographic fractionation of the extract, guided by bioassays on E. paenulata, the flavanone pinocembrin (1) was isolated as the most active principle. In a choice assay, compound 1 showed strong antifeedant activity against E. paenulata, Xanthogaleruca luteola and Spodoptera frugiperda with an AI% of 90, 94 and 91% (p<0.01) respectively, at 50 microg/cm(2). The dosages necessary for 50% feeding inhibition of the insects (ED(50)) were 7.98, 6.13 and 8.86 microg/cm(2), respectively. The feeding inhibitory activity of 1 against E. paenulata was compared with the activity of other structurally related flavonoids like naringenin, which was inactive up to 100 microg/cm(2), catechin which was nearly 6 times less active than 1, and quercetin which was equally active as 1. The effect of these on the feeding behavior of E. paenulata was also studied.

Effects of Melia azedarach on Triatoma infestans

Extracts from fruits and leaves of Melia azedarach were tested for repellent and insecticidal properties against eggs and nymphs of Triatoma infestans, the vector of Chagas disease. Unripe fruit extract was highly repellent for first and fourth instar nymphs. Ripe fruit had a weaker effect while leaves were ineffective. No effects on egg hatching, nymph survival or development time were detected, but first instar nymphs reared in contact with extract-treated refuges were significantly smaller than controls after moulting.

Antibacterial activity of extracts from plants of central Argentina--isolation of an active principle from Achyrocline satureioides.

The great increase in bacterial infections is fueling interest in the search for antibacterial products of plant origin. Extracts obtained from 51 native and naturalized plants from central Argentina were therefore evaluated for their IN VITRO inhibitory activity on pathogenic bacteria with the aim of selecting the most active ones as new sources of effective antibiotics. The susceptibility of reference and clinical strains of Enterococcus faecalis, Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Salmonella enterica serovar Enteritidis, and Staphylococcus aureus was determined. Extracts from Achyrocline satureioides, Flourensia oolepis, Lepechinia floribunda, and Lithrea molleoides were the most potent, with MIC and MBC values ranging from 0.006 to 2 and 0.012 to 10 mg/mL, respectively, on both gram-positive and negative bacteria. The antibacterial activity-guided isolation of A. satureioides ethanol extract showed 23-methyl-6-O-desmethylauricepyrone (1) to be the most active compound. This compound showed inhibitory effects against gram-positive bacteria with MIC and MBC values of 0.002 and 0.008 mg/mL, respectively, while on gram-negative strains, the MIC and MBC were 0.062-0.250 and 0.062-0.500 mg/mL, respectively. The strong antibacterial activity shown by the four plant extracts or the compound isolated from A. satureioides suggests that they could become part of the arsenal of antibacterial drugs currently used.

Antifungal activity of Melia azedarach fruit extract

Abstract The ethanol extract of Melia azedarach ripe fruits showed fungistatic (MIC 50–300 mg/ml) and fungicidal (MFC 60–500 mg/ml) against Aspergillus flavus, Fusarium moniliforme, Microsporum canis and Candida albicans.

Screening for acetylcholinesterase inhibitory activity in plant extracts from Argentina

Plants are a potential source of bioactive compounds and offer a promising strategy for the treatment of neurological disorders such as Alzheimers disease.

INSECTICIDE PROPERTIES OF THE ESSENTIAL OILS FROM HAPLOPAPPUS FOLIOSUS AND BAHIA AMBROSOIDES AGAINST THE HOUSE FLY, MUSCA DOMESTICA L

The compositions of the essential oils (EO’s) obtained by hydro distillation from fresh leaves of haplopappus foliosus and bahia ambrosoides was analyzed by gas chromatography/mass spectroscopy (GC/MS). The insecticidal activity of each oil against the house fly Musca domestica was evaluated by placing flies in a glass jar with a screw cap that held a piece of EO-treated cotton yarn. The dose necessary to kill 50% of flies (LC 50 ) in 1 h was determined at 26±1°C. The essential oil from haplopappus foliosus was the most potent insecticide (LC 50 = 4.43 mg/dm 3), wile the EO from bahia ambrosoides shows only moderated insecticide activity (LC 50 = 19.27 mg/dm3). According to GC and GC/MS analysis, limonene (28,00%); epi-bicyclosesquiphellandrene (9,84%); bornyl acetate (7,74%); 4-terpineol (6,36%); p-cymene (6,00%); agarospirol (5,53%); α-muurolene (4,34%); δ-cadinene (3,98%) and caryophyllene (3,97%) were the principal components of haplopappus foliosus EO and limonene (28,16%); α-pinene (11,12%); germacrene D (8,81%); sabinene (5,93%); α-thujene (3,48%); γ-curcumene (3,45%) y α-bergamotene (3,36%) were the principal components of bahia ambrosoides EO. The EO from haplopappus foliosus seem promising as a natural insecticide against houseflies and the difference with the activity of the EO of bahia ambrosoides can be ascribed to the content of oxygenated monoterpenoids and sesquiterpenoids.

Fumigant toxicity of Citrus sinensis essential oil on Musca domestica L. adults in the absence and presence of a P450 inhibitor.

Essential oils (EOs) are potential tools for controlling Musca domestica L. In a fumigant assay, M. domestica adults treated with Citrus sinensis EO (LC50=3.9mg/dm(3)), with (4R)(+)-limonene (95.1%) being its main component, died within 15min or less. The terpenes absorbed by the flies and their metabolites, analyzed using SPME fiber, were (4R)(+)-limonene (LC50=6.2mg/dm(3)), α-pinene (LC50=11.5mg/dm(3)), β-pinene (LC50=6.4mg/dm(3)), and two new components, carveol (LC50=1122mg/dm(3)) and carvone (LC50=19mg/dm(3)), in a proportion of 50, 6.2, 12.5, 6.3 and 25%, respectively. Carveol and carvone were formed by oxidation of (4R)(+)-limonene mediated by cytochrome P450, as was suggested by a fumigation assay on flies previously treated with piperonyl butoxide, a P450 inhibitor. In this experiment, an increase in the toxicity of the EO and (4R)(+)-limonene was observed, as well as a lower production of carveol and carvone.

Molecular response of Musca domestica L. to Mintostachys verticillata essential oil, (4R)(+)-pulegone and menthone

Intense applications of synthetic insecticides for the control of adult Musca domestica have led to the insects developing resistance to most of them. In consequence, there is interest in new active ingredients as alternatives to conventional insecticides. Essential oils (EO) are potential tools for controlling M. domestica because of their effectiveness and their minimal environmental effects. In a fumigant assay, M. domestica adults treated with Minthostachys verticillata EO [LC(50)=0.5 mg/dm(3); majority components by SPME-GC: (4R)(+)-pulegone (67.5%), menthone (22.3%) and (4R)(+)-limonene (3.8%)], died within 15 min or less. The terpenes absorbed by the flies and their metabolites, analyzed using SPME fiber, were (4R)(+)-limonene (LC(50)=6.2 mg/dm(3)), menthone (LC(50)=1.9 mg/dm(3)), (4R)(+)-pulegone (LC(50)=1.7 mg/dm(3)) and a new component, menthofuran (LC(50)=0.3 mg/dm(3)), in a relative proportion of 12.4, 6.5, 35.9 and 44.2% respectively. Menthofuran was formed by oxidation of either (4R)(+)-pulegone or menthone mediated by cytochrome P450, as demonstrated by a fumigation assay on flies previously treated with piperonyl butoxide, a P450 inhibitor, which showed a decrease in toxicity of the EO, (4R)(+)-pulegone and of menthone, supporting the participation of the P450 oxidizing system in the formation of menthofuran. The enzymatic reaction of isolated fly microsomes with the EO or the (4R)(+)-pulegone produced menthofuran in both cases. Contrary to expectations, the insect detoxification system contributed to enhance the toxicity of the M. verticillata EO. Consequently, resistant strains overexpressing P450 genes will be more susceptible to either M. verticillata EO or (4R)(+)-pulegone and menthone.