Bioactivity of Deverra tortuosa essential oil, its nanoemulsion, and phenylpropanoids against the cowpea weevil, a stored grain pest with eco-toxicological evaluations.

The essential oil (EO) was hydrodistilled from of Deverra tortuosa aerial parts. Fifty-six components amounting 99.3% were identified in EO through using gas chromatography-flame ionization detection (GC-FID) and (GC-MS). Phenylpropanoids, dillapiole (41.6%), elemicin (7.3%) and myristicin (5.1%), and the monoterpene, sabinene (4.2%) were identified as the major terpenes. An oil-in-water nanoemulsion (particle size 70.3 nm) was developed from EO adopting a low-energy method. The EO products showed insecticidal and biochemical effects against the cowpea weevil Callosobruchus maculatus. Based on a 48-h exposure period, the oil nanoemulsion exhibited a superior contact bioactivity (LC50 = 10.3 µg/cm2), followed by EO (LC50 = 23.1 µg/cm2), dillapiole (LC50 = 27.8 µg/cm2), and myristicin (LC50 = 37.1 µg/cm2). Upon fumigation, nanoemulsion and EO were superior as fumigants (LC50 after 48 h were 6.9 and 14.3 µl/l, respectively). Test materials showed a residual bioactivity against C. maculatus, where EO, dillapiole, and myristicin showed the strongest grain protecting activity. EO products significantly inhibited acetylcholinesterase (AChE) activity of C. maculatus adults. Test products were safe toward the non-target earthworms and did not alter the viability of cowpea seeds. There are evidences for the potential of using EO of D. tortuosa and its nanoemulsion and phenylpropanoids as natural grain protectants against C. maculatus.

Bioactivity and safety evaluations of Cupressus sempervirens essential oil, its nanoemulsion and main terpenes against Culex quinquefasciatus Say.

The essential oil (EO) of Cupressus sempervirens was obtained by hydrodistillation and analysed using gas chromatography-flame ionization detection (GC-FID) and gas chromatography-mass spectrometry (GC-MS). Two monoterpenes, α-pinene (49.1%) and δ-3-carene (21.4%), and one sesquiterpene hydrocarbon, α-cedrol (5.1%), were isolated as the EO major terpenes. An oil-in-water nanoemulsion (particle size 71.2 nm) was produced from the EO through a low-energy method. The EO, its nanoemulsion and its main constituents showed mosquitocidal and biochemical effects against Culex quinquefasciatus Say, the common vector of lymphatic filariasis parasites. All treatments showed dose-dependent bioactivity, and adults were more susceptible to the EO products than the larvae. The nanoemulsion showed superior activity, followed by the crude EO and α-cedrol. At 40 µg/ml, the nanoemulsion caused 100% larval mortality, while the EO and α-cedrol required twice this concentration to achieve the same larval mortality. The LC50 values were 8.4, 16.1, 15.1, 30.7 and 53.4 µg/ml at 24 h after exposure for the nanoemulsion, crude oil, α-cedrol, δ-3-carene and α-pinene, respectively. For adults, 20.0 µl/l nanoemulsion caused 100% mortality, while twice this concentration of the EO was required to achieve the same effect. The LC50's against adults ranged between 6.2 and 40.4 µl/l. EO products prominently repelled mosquitoes at concentrations between 0.75 and 6.0 µl/cm2. The EO products caused remarkable inhibition of Cx. quinquefasciatus acetylcholinesterase activity but were safer towards the non-target aquatic species Gambusia affinis. These results recommend the use of C. sempervirens EO, its nanoemulsion and main terpenes as natural tools to control Cx. quinquefasciatus.

The essential oil of Schinus terebinthifolius and its nanoemulsion and isolated monoterpenes: investigation of their activity against Culex pipiens with insights into the adverse effects on non-target organisms.

BACKGROUND: The house mosquito, Culex pipiens L. is a harmful species, widespread in urban areas, and considered the primary enzootic vector of West Nile arbovirus. Widespread insecticide resistance in mosquito populations and the environmental risks and toxicity hazards of chemical pesticides make insecticides an inadequate mosquito control strategy. Seeking ecofriendly tools for mosquito control tools has become necessary. RESULTS: Essential oil (EO) was hydrodistilled from the fruits of Brazilian pepper, Schinus terebinthifolius Raddi and analyzed using gas chromatography-flame ionization detection and gas chromatography-mass spectrometry. An oil-in-water nanoemulsion (particle size 41.3 nm) was developed and characterized from EO using a green low-energy approach. EO, its nanoemulsion and monoterpenes showed mosquitocidal, repellent and acetylcholinesterase inhibitory activities against Cx. pipiens. A nanoemulsion concentration of 30 µl L-1 caused 100% larval mortality after 24 h of exposure, whereas EO, d-limonene and α-phellandrene at 60 µl L-1 caused 100%, 92.4% and 88.2% larval mortality, respectively. The concentration that killed 50% of organisms (LC50 ) for larvae after 24 h ranged between 6.8 and 40.6 µl L-1 . Upon fumigation, 15.0 µl L-1 of nanoemulsion killed 94.5% of adults after 24 h of exposure. LC50 values against adults ranged between 5.3 and 31.2 µl L-1 . EO products exhibited repellence activity at concentrations between 0.5 and 4.0 µl cm-2 . Test materials effectively inhibited the acetylcholinesterase activity of mosquito and were safe toward the non-target organisms Gambusia affinis and Eisenia fetida. CONCLUSION: There is a potential for using S. terebinthifolius EO, its nanoemulsion and monoterpenes as ecofriendly natural mosquitocides.

Chemical profile, characterization and acaricidal activity of essential oils of three plant species and their nanoemulsions against Tyrophagus putrescentiae, a stored-food mite.

Essential oils of Ocimum basilicum (L.), Achillea fragrantissima (Forssk.) and Achillea santolina (L.) were obtained by hydrodistillation and analyzed using gas chromatography (GC) and GC/mass spectrometry (MS). Oil-in-water nanoemulsions (10% active ingredient) were prepared through a high-energy (ultrasonication) emulsification process. Nanoemulsions were characterized by viscosity, pH, thermodynamic stability, droplet size, polydispersity index (PDI) and scanning electron microscopy (SEM) measurements. The plant oils and their nanoemulsions showed considerable acaricidal activity against the mold mite, Tyrophagus putrescentiae (Schrank) (Sarcoptiformes: Acaridae). In a contact toxicity bioassay and 48 h post treatment, O. basilicum oil was the most toxic, followed by A. fragrantissima and A. santolina, where LC50 values were 8.4, 14.1 and 21.8 µl/cm2, respectively. LC50 for benzyl benzoate, a standard acaricide was 9.8 µl/cm2. Upon fumigation, responses also varied according to the test oil. Based on the 48-h LC50 values, the same manner of activity was also observed, where O. basilicum was the most toxic followed by A. fragrantissima and A. santolina. When prepared as nanoemulsions (particle size from 78.5 to 104.6) and tested as fumigants, toxicity of the oils was increased drastically with LC50 values of 2.2, 4.7, and 9.6 µl/l air for O. basilicum, A. fragrantissima and A. santolina, respectively. The oils showed a moderate to strong residual acaricidal activity, where O. basilicum oil was the most effective. The results suggest that appropriate nanoemulsions containing the tested oils can be developed to control T. putrescentiae after the required toxicological assessments.

Comparing six mathematical link function models of the antifeedant activity of lesser grain borer exposed to sub-lethal concentrations of some extracts from calotropis procera.

In the present study, Probit, Cauchy Fractional and three types of Log methods, i.e., Logit, Log-log, and Complementary log-log were employed to model the feeding deterrence of the lesser grain borer, Rhyzopertha dominica (F) (Coleoptera: Bostrichidae), when fed latex protein, crude flavonoid fraction, 3-O-rutinosides of quercetin, kaempferol and isorhamnetin, isolated from Calotropis procera (Ait.) (Gentianales: Asclepiadaceae). A nutritional study with treated flour discs at sub-lethal concentrations indicated that the tested natural products negatively affected the feeding behavior of the lesser grain borer, causing high feeding deterrent indices. Our results assure that Probit, Logit and Clog-log model the feeding deterrent indices with high goodness of fit. The models aim to support the management of the test insect when fed grains treated with sub-lethal doses of the tested phytochemicals in order to develop a viable, precise and long-term strategy to minimize the excessive reliance on the chemical pesticides currently in use.

Ecofriendly Synthesis of Silver Nanoparticles Using Potato Steroidal Alkaloids and Their Activity Against Phytopathogenic Fungi

ABSTRACT In order to reduce the excessive reliance on the toxic chemical fungicides, the present study aimed to isolate the total potato glycoalkaloids (TPAs), and the two steroidal alkaloids α-chaconine and α-solanine from potatoes, Solanum tuberosum L. Their structures were characterized using physical and spectroscopic methods including (UV, IR, 1H, 13C--NMR, 2D 1H-1H COSY, HMBC and NOESY). Silver nanoparticles (AgNPs) were prepared from potato alkaloids through a green synthesis approach. Potato alkaloids and their nanoparticles inhibited mycelial growth of the phytopathogenic fungi Alternaria alternate, Rhizoctonia solani, Botrytis cinerea and Fusarium oxysporum f. sp. lycopersici with low minimal inhibitory and minimal fungicidal concentrations. R. solani was the most susceptible, while F. oxysporum was the most resistant. TPAs was the most fungitoxic (EC50's were 19.8, 22.5, 26.5 and 32.3 µg/ml against R. solani, A. alternate, B. cinerea and F. oxysporum respectively). A mixture of α-solanine and α-chaconine (1:1) showed a marked antifungal activity. AgNPs (size 39.5-80.3 diameter) from alkaloids showed improved fungitoxic activity (EC50's of TPAs nanoparticles ranged between 10.9 and 16.1 µg/ml). Alkaloids exhibited no or a slight phytotoxicity against wheat and radish. Results recommend the potential of using potato alkaloids and their nanoparticles as biorational alternatives to conventional fungicides.

Mathematical probit and logistic mortality models of the Khapra beetle fumigated with plant essential oils.

In the current study, probit and logistic models were employed to fit experimental mortality data of the Khapra beetle, Trogoderma granarium (Everts) (Coleoptera: Dermestidae), when fumigated with three plant oils of the gens Achillea. A generalized inverse matrix technique was used to estimate the mortality model parameters instead of the usual statistical iterative maximum likelihood estimation. As this technique needs to perturb the observed mortality proportions if the proportions include 0 or 1, the optimal perturbation in terms of minimum least squares (L2) error was also determined. According to our results, it was better to log-transform concentration and time as explanatory variables in modeling mortality of the test insect. Estimated data using the probit model were more accurate in terms of L2 errors, than the logistic one. Results of the predicted mortality revealed also that extending the fumigation period could be an effective control strategy, even, at lower concentrations. Results could help in using a relatively safe and effective strategy for the control of this serious pest using alternative control strategy to reduce the health and environmental drawbacks resulted from the excessive reliance on the broadly toxic chemical pesticides and in order to contribute safeguard world-wide grain supplies.

Toxic and antifeedant activities of prenylated flavonoids isolated from Tephrosia apollinea L. against three major coleopteran pests of stored grains with reference to their structure-activity relationship.

Four prenylated flavonoids, isoglabratephrin, (+)-glabratephrin, tephroapollin-F and lanceolatin-A, were isolated from Tephrosia apollinea L. and tested against three stored grain insects. Using the filter paper bioassay, compounds showed adulticidal activity against Sitophilus oryzae (L), Rhyzopertha dominica (F) and Tribolium castaneum (Herbst) at concentrations of 0.875, 1.75 and 3.5 mg mL(- 1). At 3.5 mg mL(- 1), tephroapollin-F was the most toxic (78.6%, 64.6% and 60.7% mortality was recorded after 10 days exposure of S. oryzae, R. dominica and T. castaneum, respectively). The F1 progeny production of insects was affected after parental exposure to flavonoids, where S. oryzae was the most susceptible. A nutritional bioassay, employing a flour disc and test concentrations of 0.65, 1.3 and 2.6 mg g(- 1), revealed a significant reduction in the relative growth rate, relative consumption rate and efficiency of conversion of ingested food by all insects. The structure-activity relationship among the tested flavonoids was discussed.