Repellent Activity Research Articles

Betel essential oil-loaded lipid-core nanocapsules as mosquito repellent spray formulations for fabric finishes

In the present study, poly(ε-caprolactrone) nanocapsules were loaded with betel essential oil and used as anti-mosquito spray formulations for cotton and polyester fabrics for the first time. The release and retention of betel essential oil on the fabrics after sequential washing and heating were determined using UV-Visible spectrophotometry. The repellent activity of cotton and polyester fabrics was evaluated using an Excito chamber test on Aedes aegypti mosquitoes. The nanocapsules exhibited high betel essential oil encapsulation efficiency (98.70%) and remained stable throughout 60 days of colloidal system stability study. The encapsulation of betel essential oil in the lipid core of polymer nanocapsules was able to increase the durability towards washing and heating, as the fabrics still exhibited a good repellency of up to 47% against mosquitoes even after 5 sequential washing cycles. Results obtained from this study highlight the feasibility of betel essential oil-loaded lipid-core nanocapsules as alternatives to mosquito repellent spray formulations in the production of insect protective fabrics.

In vitro Evaluation of PHYTOSANEB-020, A Biopesticide for the Control of Mealybug (Planococcus ficus) on Rosa multiflora and Bougainvillea spectabilis in Kimwenza-Mission

This study focused on the in vitro evaluation of the effectiveness of Phytosaneb-020, a bio-pesticide on Mealybug Planococcus ficus (Signoret) which infests Rosa multiflora (Rosa polyantha) and Bougainvillea spectabilis. Three treatments were used: Phytosaneb-020, Pacha a chemical insecticide and aqueous solution (distilled water) as a negative control. A volume of 1.5 mL for an area of ​​56.72 cm2 corresponding to the area of ​​a Petri dish, used for each treatment. Populations of Maconellicoccus hirsutus were carefully collected from bougainvillea leaves and roses. Pacha gave the highest mortality percentage for direct toxicity by contact (98.3± 2.89%) followed by Saneb-020 (93.3 ± 7.64%). The negative control, distilled water, was not effective against the insects. No death was observed (0%). The repellency effect assay revealed a repellent activity of 80% ± 20 for Saneb-20. Distilled water gave the best avoidance effect (86.7±11.6%) pointing out the fact that Mealybug Planococcus ficus doesn’t support the presence of water. Pasha exhibited low repellency effect on Mealybug Planococcus ficus (46.7±41.6%). Further investigations on different pests are strongly suggested and encouraged to improve the effectiveness of this biopesticide.

One-step zwitterionization and quaternization of thick PDMAEMA layer grafted through subsurface-initiated ATRP for robust antibiofouling and antibacterial coating on PDMS

In this work, we demonstrate the grafting of thick poly((2-dimethylamino) ethyl methacrylate) (PDMAEMA) layer on PDMS via subsurface-initiated atom transfer radical polymerization (SSI-ATRP). The self-migration of DMAEMA monomers into the subsurface of PDMS is proven to be the dominant factor for the success of SSI-ATRP. The as-prepared thick microscale graft layer on PDMS shows much better abrasion resistance than nanoscale graft layer obtained by conventional surface-initiated atom transfer radical polymerization (SI-ATRP) under identical condition. Taking advantage of the tertiary amines of PDMAEMA, the simultaneous zwitterionization and quaternization of the PDMAEMA thick layer is realized through a facile one-step process. The effect of zwitterionization and quaternization degree on the antibiofouling and antibacterial properties is investigated. The results show that a relatively high zwitterionization degree (75 mol%) and a low quaternization degree (25 mol%) exhibit a good well-balanced effect on both fouling repellence and bactericidal activity. This work may lead to the development of robust bifunctional antibiofouling and antibacterial surfaces via SSI-ATRP strategy.

Insecticidal activities of indigenous plants from Volta Region, Ghana in managing Sitophilus zeamais and Prostephanus truncatus in stored maize

Abstract. Ankutse DK, Eziah VY, Afreh-Nuamah K. 2021. Insecticidal activities of indigenous plants from Volta Region, Ghana in managing Sitophilus zeamais and Prostephanus truncatus in stored maize. Intl J Trop Drylands 5: 48-60. The rising rate of pest resistance, and the high expense and health risks associated with insecticide use, have become a source of public concern. This study aimed to discover and evaluate plant species used by farmers in the Volta Region to control Sitophilus zeamais (Motschulsky, 1855) and Prostephanus truncatus (Horn, 1878) in stored maize grains. In a survey, Azadirachta indica, Clausena anisata, Phyllanthus amarus, Picralima nitida, Vernonia amygdalina, Nauclea latifolia, and Momordica charantia were discovered to be grain protectants against stored insect pests. All of the plants indicated above were employed in the experiment, except for A. indica, which has a long history of being used to combat grain storage pests. The insecticidal activity of dried powders (5 and 10%) and aqueous extracts (0.1 and 0.2 g/mL) of plants against P. truncatus and S. zeamais was examined. Plant species and dose rate influenced repellency. In the V. amygdalina treatment, plant powders and methanol extracts were the most poisonous to insects. The toxicity of V. amygdalina to P. truncatus and S. zeamais was 83.3 and 86.7%, respectively, at higher concentrations of 0.2 g/mL. At 0.2 g/mL, all plant extracts exhibited a significant difference in Actellic repellent (P0.05); nevertheless, C. anisata had the highest repellent action against P. truncatus and S. zeamais, with 80.0 and 66.7%, respectively. As grains were treated with plant extracts, oviposition and egg emergence were reduced compared to the control. When embryonic stages of insects were treated with methanol extracts of botanicals, the number of adult insects decreased. These findings show that the studied plants have the potential to aid in the development of post-harvest protection technology against the principal pests of stored grains, P. truncatus and S. zeamais. As a result, farmers should use it to control P. truncatus and S. zeamais in stored maize grains.

Essential oils used in dermocosmetics: Review about its biological activities.

Currently, the demand for the use of constituents of natural origin in cosmetic formulations in detriment of synthetic compounds is noticeable. Several studies assess the potential of essential oils when incorporated into various cosmetic formulations and study their biological activities. This work intends to prepare a literature review on essential oils tested in dermocosmetic formulations and whose biological activities were evaluated through in vitro and/or in vivo tests. The main objectives for this study were as follows: to identify the essential oils that have been used in cosmetic formulations; and compile information on the main biological activities tested in cosmetic formulations. A search was carried out until 2021 in the scientific databases PubMed and Web of Science, using different search terms, and several scientific articles from in vitro and in vivo studies in animals and clinical trials were selected and analyzed of involving development dermocosmetic formulations containing essential oils and the analysis of their biological activities. These studies demonstrate that the antimicrobial activity (antibacterial and antifungal) is the one most studied, mainly through in vitro tests. In vivo studies were also carried out either in animals or in clinical studies showing different effects, such as repellent action, inhibition of hair growth, and action against migraine. Regarding formulations, it was evident that creams are the most used. There is enormous potential for the use of essential oils in future formulations in the cosmetic and pharmaceutical industry, in particular as preservatives, exploring their other biological activities.

Novel β-Cyclodextrin and Catnip Essential Oil Inclusion Complex and Its Tick Repellent Properties.

Cyclodextrin inclusion complexes have been successfully used to encapsulate essential oils, improving their physicochemical properties and pharmacological effects. Besides being well-known for its effects on cats and other felines, catnip (Nepeta cataria) essential oil demonstrates repellency against blood-feeding pests such as mosquitoes. This study evaluates the tick repellency of catnip oil alone and encapsulated in β-cyclodextrin, prepared using the co-precipitation method at a 1:1 molar ratio. The physicochemical properties of this inclusion complex were characterized using GC-FID for encapsulation efficiency and yield and SPME/GC-MS for volatile emission. Qualitative assessment of complex formation was done by UV-Vis, FT-IR, 1H NMR, and SEM analyses. Catnip oil at 5% (v/v) demonstrated significant tick repellency over time, being comparable to DEET as used in commercial products. The prepared [catnip: β-CD] inclusion complex exerted significant tick repellency at lower concentration of the essential oil (equivalent of 1% v/v). The inclusion complex showed that the release of the active ingredient was consistent after 6 h, which could improve the effective repellent duration. These results demonstrated the effective tick repellent activity of catnip essential oil and the successful synthesis of the inclusion complex, suggesting that β-CDs are promising carriers to improve catnip oil properties and to expand its use in repellent formulations for tick management.

Semiochemical signatures associated with differential attraction of Anopheles gambiae to human feet.

BackgroundSeveral human-produced volatiles have been reported to mediate the host-seeking process under laboratory conditions, yet no effective lure or repellent has been developed for field application. Previously, we found a gradation of the attractiveness of foot odors of different malaria free individuals to Anopheles gambiae sensu stricto Giles. In this study, foot odor of the individual with the most attractive ‘smelly’ feet to the An. gambiae was collected, analyzed and attractive blend components identified.MethodsThe foot odor of the individual with the most attractive ‘smelly’ feet to the An. gambiae was trapped on Porapak Q and analyzed by gas chromatography-linked mass spectrometry (GC-MS). Specific constituents perceived by the insect olfactory system were then identified by GC-linked to electro-antennography detector (GC-EAD) and characterized by GC-MS. The contribution of each constituent to the behavioral response of An. gambiae was assessed through subtractive assays under semi-field conditions in a screen-house using Counter Flow Geometry (CFG traps) baited with (i) the blend of all the EAD-active and (ii) other blends containing all components with exclusion of one component at a time. The number of mosquitoes trapped in the baited CFG traps were compared with those in the control traps.ResultsEleven major and minor constituents: 2 carboxylic acids, six aldehydes, two ketones and one phenolic compound, were confirmed to be EAD-active. The contribution of each constituent to the behavioral response of An. gambiae was assessed through subtractive assays under semi- field conditions. Exclusion/ subtraction of one of the following compounds: i-butyric acid, i-valeric acid, n-octanal, n-nonanal, n-decanal, n-dodecanal, undecanal or n-tridecanal, from each blend led to reduction in the attractiveness of all the resulting blends, suggesting that all of them are critical/important for the attractiveness of the foot odor to An. gambiae mosquitoes. However, exclusion/subtraction of 4-ethoxyacetophenone, 4-ethylacetophenone and/or 2-methylphenol, led to significant enhancements in the attractiveness of the resulting blends, suggesting that each of these compounds had repellent effect on An. gambiae ss. Undecanal exhibited kairomonal activity at low natural concentrations under semi-field conditions but repellent activity at high unnatural conditions in the laboratory. Furthermore, the comparison of the mean mosquito catches in traps baited with the nine-component blend without 4-ethoxyacetophenone, 4-ethylacetophenone and the complete foot odor collection revealed that the former is significantly more attractive and confirmed the repellent effect of the two carbonyl compounds at low natural concentration levels.ConclusionThese results suggest that differential attractiveness of An. gambiae to human feet is due to qualitative and/or qualitative differences in the chemical compositions of the foot odors from individual human beings and relative proportions of the two chemical signatures (attractants versus repellents) as observed from the ratios of the bioactive components in the foot odors of the most attractive and least attractive individuals. Chemical signature means the ensemble of the compounds released by the organism in a specific physiological state. The chemical signature is emitter-dependent, but does not depend on receiver response. Thus, there is only one chemical signature for one individual or species that may eventually include inactive, attractive and repellent components for another organism. The nine-component attractive blend has a potential as an effective field bait for trapping of malaria vectors in human dwellings.

Acaricidal activity of Foeniculum vulgare against Rhipicephalus annulatus is mainly dependent on its constituent from trans-anethone.

Globally, the economic losses due to hard ticks infestation and the control of the associated diseases have been calculated at USD $13.9–18.7 billion per year. The economic impact is related to its direct damage to the skins, blood loss, anemia, severe immunological reactions and indirect losses that related to the effects of hemoparasites, cost of treatment for clinical cases and expenses incurred in the control of ticks. The current study evaluated the acaricidal activities of fennel Foeniculum vulgare essential oil and its main components; trans-anethole and fenchone; against R. annulatus. GC–MS analysis revealed that this oil contained 16 components representing 99.9% of the total identified compounds with E-anethole being the predominant component(64.29%), followed by fenchone (9.94%). The fennel oil and trans-anethole showed significant acaricidal activities. The LC50 of the fennel oil was attained at concentrations of 12.96% for adult ticks and 1.75% for tick larvae meanwhile the LC50 of trans-anethole was reached at concentrations of 2.36% for adult tick and 0.56% for tick larvae. On the contrary, fenchone showed no any significant adulticidal activities and its LC50 attained at a concentration of 9.11% for tick larvae. Regarding repellence activities, trans-anethole achieved 100% repellency at the concentration of 10% while fennel showed 86% repellency at the same concentration. Fenchone showed no repellency effect. Treatment of larvae with fennel, trans-anethole, and fenchone LC50 concentrations significantly inhibited the acetylcholinesterase activity. Meanwhile, glutathione s-transferase activity was significantly decreased in fennel treated larvae but no significant effect was found in the larvae of trans-anethole and fenchone groups. These results indicate that the acaricide effect of fennel oil may attributed to its high content of trans-anethole. This was supported by potent adulticidal, larvicidal, and repellency effects of trans-anethole against Rhipeciphalus annulatus tick and therefore it could be included in the list of acaricide of plant origin.

Acaricidal and repellent activities of Litsea cubeba (Lour.) oil and 3,7-dimethyl-2,6-octadienal against Haemaphysalis longicornis (Acari: Ixodidae)

The bioactivity of the essential oil extracted from Litsea cubeba fruits against tick vectors of severe fever with thrombocytopenia syndrome is unknown. In this study, L. cubeba oil and its main constituents, 3,7-dimethyl-2,6-octadienal and its similar structures, were evaluated for their acaricidal and repellent activities on the unfed nymphs and adults of Haemaphysalis longicornis. L. cubeba oil displayed both acaricidal and repellent activities against both life stages. Among the constituents of L. cubeba oil, only 3,7-dimethyl-2,6-octadienal exhibited both acaricidal and repellent activities against both life stages. In a repellent bioassay, 3,7-dimethyl-2,6-octadienal and L. cubeba oil at dose of 0.08 mg/cm2 provided excellent repellence (100%) against the nymphs and adults for over 60 min post-application. When the acaricidal and repellent activities of 3,7-dimethyl-2,6-octadienal and its similar structures were compared, activities of all tested derivatives were significantly less potent than those of 3,7-dimethyl-2,6-octadienal. The strong acaricidal and repellent activities of 3,7-dimethyl-2,6-octadienal in L. cubeba oil suggests that it is a promising natural candidate for developing new sustainable acaricidal and repellent agents.

Antimicrobial and anti-dust mite efficacy of Cinnamomum camphora chvar. Borneol essential oil using pilot-plant neutral cellulase-assisted steam distillation.

Cinnamomum camphora chvar. Borneol essential oil (BEO) was efficiently extracted by using pilot-plant neutral cellulase-assisted steam distillation (NCSD). Borneol, β-cadinene and α-caryophyllene were identified as major components. Bacillus subtilis was the most sensitive bacteria to BEO with the lowest minimal inhibition concentration (MIC) and minimal bactericial concentration (MBC) at 1·75 and 3·50mgml-1 , respectively. Antimicrobial activity of the BEO was also reasonably high against Salmonella typhimurium, Escherichia coli and Staphylococcus aureus, but not sensitive against two fungi, i.e. Aspergillus niger and Penicillium aurantiogriseum. Changes in permeability and integrity of cell membrane, damage of cell wall and further leakage out of metabolites and ions were determined as bactericidal mechanisms of BEO against the two gram-positive bacteria. The BEO showed a reasonably high repelling activity of dust mite, which achieved higher than 95% repelling dust mite activity after the treatment of BEO solution at 0·50mgml-1 . When the concentration of BEO was higher than 0·50mgml-1 , it was B-grade miticide with miticidal activity higher than 95%. Miticidal procedures were characterized as excitation, contraction, relaxation and lastly leading to the death of dust mite. It is speculated that the BEO would cause dehydration and death of dust mite as neuromuscular toxicity.

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.

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. 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 41.3nm) 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 40.6μl L-1 . Upon fumigation, 15.0μl L-1 of nanoemulsion killed 94.5% of adults after 24 h of exposure. LC50 values against adults ranged between 5.3 and 31.2μl L-1 . EO products exhibited repellence activity at concentrations between 0.5 and 4.0μl cm-2 . Test materials effectively inhibited the acetylcholinesterase activity of mosquito and were safe toward the non-target organisms Gambusia affinis and Eisenia fetida. There is a potential for using S. terebinthifolius EO, its nanoemulsion and monoterpenes as ecofriendly natural mosquitocides.

Biosynthesized Gold Nanoparticles Integrated Ointment Base for Repellent Activity Against Aedes aegypti L.

The present study focused on preparing a nano-ointment base integrated with biogenic gold nanoparticles from Artemisia vulgaris L. leaf extract. As prepared, nano-ointment was characterized by using Fourier-transform infrared spectroscopy, and the morphology of the nano-ointment was confirmed through a scanning electron microscope. Initially, the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide results showed nano-ointment cytocompatibility at different concentrations (20-200μg/mL) against L929 cells. The in vitro hemolysis assay also revealed that the nano-ointment is biocompatible. Further studies confirmed that nano-ointment has repellent activity with various concentrations (12.5, 25, 50, 75, and 100ppm). At 100ppm concentration, the highest repellent activity was observed at 60-min protection time against the Aedes aegypti L. female mosquitoes. The results indicated that the increasing concentration of nano-ointment prolongs the protection time. Moreover, the outcome of this study provides an alternative nano-ointment to synthetic repellent and insecticides after successful clinical trials. It could be an eco-friendly, safer nano-bio repellent, which can protect from dengue fever mosquitoes.

Repellent Activity of Cymbopogon citratus Essential Oil Against Four Major Stored Product Pests: Plodia interpunctella, Sitophilus oryzae, Acanthoscelides obtectus and Tribolium castaneum

Summary The purpose of this study is to assess the repellent activity of lemongrass (Cymbopogon citratus) essential oil (EO), grown in Serbia under greenhouse conditions, against four prevalent stored product pests: Plodia interpunctella (larvae), Sitophilus oryzae, Acanthoscelides obtectus and Tribolium castaneum (adults). The lemongrass EO repellency was tested using filter paper in Petri dishes and a Y-tube olfactometer. According to the repellency index (RI), the lemongrass EO repellency was divided into 5 classes. Prior to biotesting, the chemical characterization of lemongrass EO was performed and the following main compounds were detected: myrcene (31.0%), geranial (30.0%), and neral (23.6%). The C. citratus EO considered was found to exhibit the Class III repellent activity against P. interpunctella larvae only at the highest concentration (namely 0.5%). This is the very first report on the C. citratus EO repellent activity against this pest. The lemongrass EO examined showed strong repellency (Class IV) against S. oryzae (0.2% and 0.5% of EO), A. obtectus (0.1% and 0.2%), and T. castaneum (0.05-0.1%). Moreover, higher lemongrass EO concentrations (0.5%) were found to exhibit extreme repellency (Class V) against A. obtectus and T. castaneum. The results obtained were confirmed in the bioassays performed, indicating the great potential of lemongrass EO as a bio-repellent when applied in higher concentrations to all the insects considered, regardless of the exposure period.

Superhydrophobic Materials for Advanced Healthcare

Superhydrophobic surfaces are known for a vast array of industrial applications. These surfaces and coatings are now increasingly finding applications in the biomedical sector. Such applications include substrates to control protein adsorption, cellular interaction, and bacterial growth and blood repellent actions. Superhydrophobic surfaces can be leveraged to develop advanced biotechnology platforms for drug delivery devices and also for diagnostic tools. In this short perspective, we have presented some of the most relevant recent research developments that have been reported on superhydrophobic biomedical surfaces and coatings and that have been considered significant in advanced healthcare.

Insecticidal, Repellent and Antifeedant Activity of Essential Oils from Blepharocalyx cruckshanksii (Hook. & Arn.) Nied. Leaves and Pilgerodendron uviferum (D. Don) Florin Heartwood against Horn Flies, Haematobia irritans (Diptera: Muscidae).

Haematobia irritans is a cosmopolitan obligate blood-feeding ectoparasite of cattle and is the major global pest of livestock production. Currently, H. irritans management is largely dependent on broad-spectrum pesticides, which has led to the development of insecticide resistance. Thus, alternative control methods are needed. Essential oils have been studied as an alternative due to their wide spectrum of biological activities against insects. Thus, the main aim of this study was to evaluate the insecticidal, repellent and antifeedant activity of the essential oils from Blepharocalyx cruckshanksii leaves and Pilgerodendron uviferum heartwood against horn flies in laboratory conditions. The composition of the essential oils was analyzed using gas chromatography coupled to mass spectrometry. Accordingly, α-pinene (36.50%) and limonene (20.50%) were the principal components of the B. cruckchanksii essential oil, and δ-cadinol (24.16%), cubenol (22.64%), 15-copaenol (15.46%) and δ-cadinene (10.81%) were the most abundant compounds in the P. uviferum essential oil. Mortality of flies and feeding behavior were evaluated by non-choice tests, and olfactory response was evaluated using a Y-tube olfactometer. Both essential oils were toxic to horn flies, with LC50 values for B. cruckchanksii essential oil of 3.58 µL L−1 air at 4 h, and for P. uviferum essential oil of 9.41 µL L−1 air and 1.02 µL L−1 air at 1 and 4 h, respectively. Moreover, the essential oils exhibited spatial repellency in the olfactometer using only 10 µg of each oil, and these significantly reduced the horn fly feeding at all doses evaluated. Although further laboratory and field studies related to the insectistatic and insecticide properties of these essential oils against H. irritans are necessary, B. cruckshanksii leaves and P. uviferum heartwood essential oils are promising candidates for horn fly management.

Chemical components and insecticidal effects of essential oils from three lavender cultivars against adult Sitophilus granarius (L., 1758) (Coleoptera: Curculionidae)

The study was conducted to determine the insecticidal and behavioral effect of essential oils (EOs) extracted from three lavender cultivars, Hemus, Raya and Yubileina, against adult stage of Sitophilus granarius (L., 1758) (Coleoptera: Curculionidae) under laboratory conditions. The contact, fumigant and repellent effects of plant EOs were investigated and possible germination inhibitory effects of the EOs on wheat germination were evaluated. EOs were extracted from the plant samples using a Neo-Clevenger type apparatus where the plant material is subjected to hydro distillation. The chemical constituents of EOs were detected by gas chromatography-mass spectrometry. The experiments were conducted under laboratory conditions in 2019 and 2020. As a result of the study, it was determined that the fumigant activity changed according to the cultivars. While the LC90 value in the fumigant activity of the EOs of the Hemus was determined as 0.157 µl/ml air, this value was recorded as 0.139 µl/ml air and 0.118 µl/ml air in Raya and Yubileina, respectively. Six h after treatment, the highest repellent activity was 86% at 0.05 µl/cm2 with Yubileina. Main EOs components of each cultivar were: Yubileina, linalool (36.0%), linalyl acetate (24.2%) and lavandulyl acetate (5.86%); Hemus, linalool (28.5%), linalyl acetate (23.1%) and lavandulyl acetate (6.59%); and Raya, linalool (42.5%), linalyl acetate (30.0%) and ɑ-terpineol (5.45%). There was no negative effect on the germination of wheat with any of essential oils. These results show that lavender EOs could be useful for the control of S. granarius .

Plant secondary metabolites extracted from Acorus calamus rhizome from Western Ghats, India and repellent activity on Sitophilus oryzae

Medicinal plants are widely used to treat various ailments and Acorus calamus L. is one of the medicinal plants has ethnomedicinal significance. The rhizome of A. calamus was used for the extraction of phytochemicals using various solvent. The methanol extract showed the presence of flavonoids, alkaloids, phenolic compounds, tannins, steroids, saponins, glycosides and terpenoids. Biological study reported higher antimicrobial array for methanolic extract of A. calamus than other solvent extracts. Fourier Transform Infrared Spectroscopy analysis revealed the presence of alcohol, alkenes, carbonyl, aromatic, amine, methylene, venyl, phenyl, ether, cyclic ether, aromatic cyclic ether, and primary amines. Gas chromatography - mass spectrometry analysis revealed the presence of compounds such as asarone, n-hexadecanoic acid, 9, 15-octadecadienoic acid, methyl ester, (z,z)- and 9,12-octadecadienoic acid (z,z). The methanolic extract of A. calamus was highly effective against bacteria such as, S. epidermis (5 μg/mL), P. vulgaris (5 μg/mL) and B. cereus (5 μg/mL). A. calamus extract was active against the tested Sitophilus oryzae, the insecticidal activity was dose dependence, and activity increased with higher doses and increased with incubation times. At 125, 250, 375, 500, 625 and 750 μg/cm2 concentration, the insecticidal repellent activity was 13.8 ± 1.4%, 17.4 ± 2.3%, 22.3 ± 1.7%, 31.8 ± 2.6%, 44.1 ± 1.3%, and 44.2 ± 2.4, respectively after 24 h incubation. This study has demonstrated that methanolic rhizome extracts of A. calamus has significant antimicrobial, anti-biofilm and insecticidal activity against pathogenic plant bacterial pathogens and insect pests, it could be of high agricultural and pharmacological value.

Chemical Composition and Insecticidal Activities of Mentha Longifolia and Mentha Mozaffarianii Essential Oils against Callosobruchus Maculatus

Essential oils from two species of Mentha genus, (Mentha longifolia L. and Mentha mozaffarianii Jamzad), from the mint family Lamiaceae that grow in Iran were isolated and analyzed by GC and GC-MS and their insecticidal and repellent activities were investigated against adult cowpea beetles. Mortality rates increased with increasing of the time of exposure and concentration, where M. mozaffarianii oil showed more potent toxicity. Using the topical application, LD50s values of M. mozaffarianii and M. longifolia oils at 96 h after exposure against adults were 22.7 and 39.4 μg/adult, respectively. In the fumigant test, LC50s at 96 h after exposure was between 38.5 and 55.4 µL/L air against adults, respectively. The results demonstrated that no concentration-dependent effect was observed in the test of the repellent effect and M. longifolia oil was most repellent to C. maculatus adults at 10 µl/l air (29.00%) while M. mozaffarianii oil’s repellency was 9% at a lower concentration of 5 µl/l air. The main chemical components of the M. longifolia oil were Pulegone (48.67%), Menthone (14.31%), 1, 8- Cineole (9.37%) and Camphor (6.60%) while the major constituents of oil of the M. mozaffarianii were Piperitone (23.59%), Linalool (14.44%), 1, 8- Cineole (11.77%) and Piperitenone oxide (9.39%).

Repellent activity of three essential oils against dengue and filarial vector mosquitoes

Cymbopogon nardus, Syzygium aromaticum, and Citrus sinensis have been well known to possess insecticidal activity. Here, we investigated the repellent activity of individual of three essential oils (C. nardus, S. aromaticum, C. sinensis) and a combination of essential oils (C. nardus + C. sinensis, C. nardus + S. aromaticum, and C. sinensis + S. aromaticum) against a dengue vector, Aedes aegypti and a filarial vector, Culex quinquefasciatus. The essential oils (1 mg) were smeared evenly on the surface of the left arm (three volunteers) and then subjected to 25 females of A. aegypti and C. quinquefasciatus in the cage. The number of landed mosquitos was observed every hour for 7 hours to determine the protection index (PI). The result showed that individuals of three essential oils and a combination of essential oils generated > 90% of PI until 7 hours of application for both mosquitos species tested. Overall, the data demonstrated that individual of three essential oils, i.e., C. nardus, S. aromaticum, C. sinensis, and various combinations of essential oils (C. nardus + C. sinensis; C. nardus + S. aromaticum; C. sinensis + S. aromaticum) are promising as repellent agents against A. aegypti and C. quinquefasciatus.

The Potential of a Site-Specific Delivery of Thiamine Hydrochloride as a Novel Insect Repellent Exerting Long-Term Protection on Human Skin: In-vitro, Ex-vivo Study and Clinical Assessment.

Thiamine hydrochloride (TH) was thought to exert a good insect repellent activity. The purpose of this work was to develop a formulation that releases TH in sustained regimen on human skin. Long lasting protection against mosquito bites was achieved. Pullulan acetate (PA) was used to prepare TH nanospheres. Optimal system was incorporated in Pluronic® hydrogel. Formulae were tested for in-vitro release and ex-vivo permeation. Complete protection time (CPT) was done adopting Kaplan-Meier survival function for the synthetic repellent (DEET), TH solution and nanospheres in hydrogel. Release profile of TH solution, nanospheres and nanosphere-loaded hydrogel (DG) demonstrated an added effect of DG, where t 1/2 was 11.2±1.4h. SEM for DG showed homogenous dispersion of nanospheres inside the matrix of the gel. Ex-vivo permeation showed only 0.761 ± 0.04% of TH in hydrogel permeated the skin after 12h, while 44.98 ± 3.2% permeated when TH solution was applied. Clinical study revealed a significant difference in CPT between TH solution with either DEET or (DG) (p<0.05), and no significant difference between DEET and DG with CPT 400 ± 31 and 360 ± 18min, respectively (P > 0.05). The high efficacy of TH-loaded hydrogel rendered it a successful alternative for DEET, offering long protection against mosquito bites.