Larvicidal and repellent activity of the essential oil of Coriandrum sativum L. (Apiaceae) fruits against the filariasis vector Aedes albopictus Skuse (Diptera: Culicidae)

The essential oils of many Apiaceae species have been already studied for their insecticidal and repellent properties against insect pests. In this research, the essential oil (EO) extracted from the fruits of Coriandrum sativum L. (Apiaceae) was evaluated for the first time for its larvicidal and repellent activities against the most invasive mosquito worldwide, Aedes albopictus Skuse (Diptera: Culicidae). The chemical composition of C. sativum EO was investigated by gas chromatography with electron impact mass spectrometry analysis. Coriander EO was mainly composed by monoterpene hydrocarbons and oxygenated monoterpenes, with linalool (83.6 %) as the major constituent. C. sativum EO exerted toxic activity against A. albopictus larvae: LC₅₀ was 421 ppm, while LC₉₀ was 531.7 ppm. Repellence trials highlighted that C. sativum EO was a good repellent against A. albopictus, also at lower dosages: RD₅₀ was 0.0001565 μL/cm² of skin, while RD₉₀ was 0.002004 μL/cm². At the highest dosage (0.2 μL/cm² of skin), the protection time achieved with C. sativum essential oil was higher than 60 min. This study adds knowledge about the chemical composition of C. sativum EO as well as to the larvicidal and repellent activity exerted by this EO against A. albopictus. On this basis, we believe that our findings could be useful for the development of new and safer products against the Asian tiger mosquito.     

Essential oil composition, adult repellency and larvicidal activity of eight Cupressaceae species from Greece against Aedes albopictus (Diptera: Culicidae)

The present study evaluated leaf essential oils from eight Cupresaceae species; Cupressus arizonica, Cupressus benthamii, Cupressus macrocarpa, Cupressus sempervirens, Cupressus torulosa, Chamaecyparis lawsoniana, Juniperus phoenicea, and Tetraclinis articulata for their larvicidal and repellent properties against Aedes albopictus, a mosquito of great ecological and medical importance. Based on the LC₅₀ values, C. benthamii essential oil was the most active (LC₅₀?=?37.5 mg/L) while the other tested Cupressaceae essential oils provided rather moderate toxicity against larvae (LC₅₀?=?47.9 to 70.6 mg/L). Under the used laboratory conditions, three of the essential oils (C. benthamii, C. lawsoniana, and C. macrocarpa) provided sufficient protection against mosquito adults, equivalent to the standard repellent “Deet” in the 0.2 mg/cm² dose, while C. macrocarpa assigned as the superior repellent oil in the 0.08 mg/cm² dose. Chemical analysis of the essential oils using gas chromatography and gas chromatography–mass spectrometry revealed the presence of 125 components.     

Larvicidal and repellent activity of Hyptis suaveolens (Lamiaceae) essential oil against the mosquito Aedes albopictus Skuse (Diptera: Culicidae)

Lamiaceae have traditionally been used in developing countries for their insecticidal and repellent properties against several insect species. In our research, the essential oil (EO) extracted from fresh leaves of Hyptis suaveolens (Lamiaceae), and its main constituents were evaluated for larvicidal and repellent activity against the Asian tiger mosquito, Aedes albopictus Skuse (Diptera: Culicidae), currently the most invasive mosquito worldwide. H. suaveolens EO had insecticidal activity against A. albopictus larvae and mortality was dosage dependent. At the highest dosages of 450 and 400 ppm, there were no significant differences on larval mortality, as mortality ranged between 98.33% and 93.33%, respectively. At dosages ranging from 250 to 350 ppm, mortality rates were lower and not significantly different from each other. Terpinolene was found to be the most effective pure compound. Efficacy protection from H. suaveolens EO, at dosages ranging from 0.03748 to 0.7496 μg cm⁻² of skin, was evaluated during 150 min of observation. Results indicated that this EO had a significant repellent activity (RD₅₀ = 0.00035 μg cm⁻²; RD₉₀ = 0.00048 μg cm⁻²), with differences in repellency rates, as a function of both concentration and observation time. Protection time ranged from 16 to 135 min. These results clearly evidenced that the larvicidal and repellent activity of H. suaveolens EO could be used for the development of new and safer products against A. albopictus.     

Larvicidal activity of lansiumamide B from the seeds of Clausena lansium against Aedes albopictus (Diptera: Culicidae)

The larvicidal activity of crude petroleum ether, toluene, n-butanol, ethyl acetate, acetone, and methanol extracts of the seeds of Clausena lansium was assayed for their toxicities against the early fourth instar larvae of Aedes albopictus. The larval mortality was observed after 24-h exposure. The LC₅₀ value of petroleum ether extract was 22.99 ppm, showing the best larvicidal activity among all six solvent extracts. A cinnamon amide compound lansiumamide B (N-methyl-N-cis-styrylcinnamamide) was isolated from the petroleum ether extract by column chromatographic method, which exhibited a strong larvicidal activity against the early fourth instar larvae of A. albopictus with LC₅₀ and LC₉₀ values of 0.45 and 2.19 ppm, respectively. The structure was elucidated by ¹H NMR, ¹³C NMR spectral data. The larvicidal activity against mosquito of lansiumamide B from the seed of C. lansium was evaluated for the first time.     

Evaluation of bioefficacy of three Citrus essential oils against the dengue vector Aedes albopictus (Diptera: Culicidae) in correlation to their components enantiomeric distribution

Laboratory experiments were conducted to study the bioefficacy against Ae. albopictus of three Citrus essential oils, derived from peels of Citrus sinensis, Citrus limon, and Citrus paradise and of their components. Chiral gas chromatography analysis revealed the dominant occurrence of R-(+)-limonene and (?)-??-pinene in all three essential oils while in the case of lemon oil ??-terpinene, neral, and geranial detected also among other components. The tested Citrus essential oils were toxic against mosquito larvae with LC₅₀ values ranging from 25.03 to 37.03?mg?l^?1. Among citrus essential oils components tested, ??-terpinene was the most toxic (LC₅₀?=?20.21?mg?l^?1) followed by both enantiomeric forms of limonene (LC₅₀?=?35.99 and 34.89?mg?l^?1, for R-(+)-limonene and S-(?)-limonene, respectively). The delayed toxic effects after exposure of larvae to sublethal (LC₅₀) doses were also investigated for citrus essential oils and their major component R-(+)-limonene, indicating a significant reduction of pupal survival. In repellent bioassays, lemon essential oil, S-(?)-limonene, citral (mixture of neral\geranial) and (+)-??-pinene were the most effective compared with other citrus essential oils and components against adult mosquitoes. Repellent bioassays also revealed that limonenes and ??-pinenes showed an isomer dependence repellent activity. Finally, according to enantiomeric distribution of limonene and ??- and ??-pinene, the repellency of lemon essential oil is possibly attributed to the presence of citral.     

Effect of Polygonum hydropiper L. against dengue vector mosquito Aedes albopictus L.

The present study aimed to evaluate the essential oil and an isolated compound from the leaves of Polygonum hydropiper L. against dengue vector mosquito Aedes albopictus L. The plant material was macerated and steam distilled using clavenger apparatus for oil extraction. The essential oil was tested at different concentrations of 100, 50, 25, 12.5 and 6.25 ppm concentrations against the larvae of Ae. albopictus. The isolated compound was tested for larvicidal, ovicidal, repellent, oviposition deterrent and adulticidal activities at 10, 5, 2.5, 1.25 and 0.625 ppm concentrations. The essential oil exhibited LC₅₀ values of 194.63 and 199.65 and confertifolin exhibited LC₅₀ values of 2.02 and 3.16 against the second and fourth instar larvae of Ae. albopictus, respectively. The ovicidal activity of 100 % on 0- to 6-h-old eggs, repellent activity of 320.6 min, oviposition deterrent activity of 98.51 % and adulticidal activity of 100 % at 10 ppm concentration of confertifolin were recorded. No mortality of was observed in negative control. To the best of our knowledge, this is the first report on the potential mosquitocidal activities of confertifolin against Ae. albopictus.     

The essential oil of <Emphasis Type="Italic">Zingiber officinalis</Emphasis> Linn (Zingiberaceae) as a mosquito larvicidal and repellent agent against the filarial vector <Emphasis Type="Italic">Culex quinquefasciatus</Emphasis> Say (Diptera: Culicidae)

Essential oils extracted by steam distillation from Zingiber officinalis was evaluated for larvicidal and repellent activity against the filarial mosquito Culex quinquefasciatus. The larval mortality was observed after 24 h treated for late third instar. The LC₅₀ value was 50.78 ppm. Skin repellent test at 1.0, 2.0, 3.0, and 4.0 mg/cm² concentration of Z. officinalis gave 100% protection up to 15, 30, 60, and 120 min. These results clearly reveal that the essential oil of Z. officinalis served as a potential larvicidal and repellent agent against filarial vector C. quinquefasciatus.     

Bioactivity of Dianthus caryophyllus, Lepidium sativum, Pimpinella anisum, and Illicium verum essential oils and their major components against the West Nile vector Culex pipiens

Mosquitoes constitute a severe health problem in many areas all over the world. There are many regions of the tropics and subtropics where mosquitoes are one of the main reasons for inhibiting the economic upgrade. Except nuisance, their medical importance is another matter of attention since mosquitoes are vectors for a wide variety of vector-borne diseases. Due to disadvantages of currently used chemical control methods, it is unavoidable to search for eco-friendly new molecules. We report herein the evaluation of the larvicidal effect exhibited by essential oils of Dianthus caryophyllus, Lepidium sativum, Pimpinella anisum, and Illicium verum against late third to early fourth instar mosquito larvae of Culex pipiens. Furthermore, phytochemical analysis of plant samples revealed their major compounds to be β-caryophyllene, eugenol, eucalyptol, α-terpinyl acetate, and (E)-anethole which were also tested for their potential larvicidal activity. For D. caryophyllus and L. sativum, this was the first report on the chemical composition of their essential oils. The essential oils of I. verum and P. anisum demonstrated high larvicidal activity with a LC₅₀ <18 mgL^?1. The other two essential oils of D. caryophyllus and L. sativum revealed moderate larvicidal activity, displaying a LC₅₀ value above 50 mgL^?1. Among the pure components, the most toxic were eugenol, (E)-anethole, and α-terpinyl acetate, with LC₅₀ values 18.28, 16.56, and 23.03 mgL^?1, respectively. Eucalyptol (1,8 cineole) and β-caryophyllene were inactive at concentrations even as high as 100 mgL^?1, showing the least significant activity against mosquito larvae. Results allow some rationalization on the relative importance of the major compounds regarding the larvicidal activity of selected essential oils and their potential use as vector control agents.     

Essential oil composition and larvicidal activity of Toddalia asiatica roots against the mosquito Aedes albopictus (Diptera: Culicidae)

The aim of this research was to determine larvicidal activity of the essential oil derived from roots of Toddalia asiatica (L.) Lam. and the isolated constituents against the larvae of the Culicidae mosquito Aedes albopictus. Essential oil of T. asiatica roots was obtained by hydrodistillation and analyzed by GC and GC-MS. A total of 58 components of the essential oil of T. asiatica roots were identified. The essential oil has almost same content of (35.41 %) of sesquiterpenoids and monoterpenoids (31.87 %). The principal compounds in T. asiatica essential oil were geraniol (9.84 %), d-limonene (7.52 %), isopimpinellin (6.62 %), α-gurjunene (6.25 %), and 4-vinylguaiacol (5.94 %). Based on bioactivity-directed fractionation, geraniol, d-limonene, and isopimpinellin were isolated from T. asiatica root essential oil. Geraniol, d-limonene, and isopimpinellin exhibited strong larvicidal activity against A. albopictus with LC₅₀ values of 30.13, 19.84, and 32.05 μg/ml, respectively, while the essential oil of T. asiatica had an LC₅₀ value of 69.09 μg/ml. The result indicated that the essential oil of T. asiatica roots and the three isolated constituents have potential for use in control of A. albopictus larvae and could be useful in search of newer, safer, and more effective natural compounds as larvicides.     

Essential oils and their compounds as Aedes aegypti L. (Diptera: Culicidae) larvicides: review

This review aims to describe essential oils and their constituent compounds that exhibit bioactivity against Aedes aegypti L. (Diptera: Culicidae) larvae, the immature stage of the primary vector of dengue. This review is based on original articles obtained by searching on major databases. Our literature review revealed that 361 essential oils from 269 plant species have been tested for their larvicidal activity. More than 60 % of these essential oils were considered active (LC₅₀?<?100 mg/L), and the majority of these active oils were derived from species belonging to Myrtaceae, Lamiaceae, and Rutaceae. The most active essential oils exhibited effective concentrations comparable with the dosage recommended for the use of temephos in container breeding. Approximately 27 % of the plants studied for their larvicidal activity against A. aegypti were collected in Brazil. Essential oils rich in phenylpropanoids, oxygenated sesquiterpenes, and monoterpene hydrocarbons were found to be the most active. When the isolates were tested, phenylpropanoids and monoterpene hydrocarbons were the most active compound classes. We describe the plant parts used and the major constituents of the essential oils. In addition, we discuss factors affecting the activity (such as plant parts, age of the plant, chemotypes, larval source, and methods used), structure–activity relationships, and mechanisms of action of the essential oils and their compounds. Essential oils have been widely investigated and show high larvicidal activity against A. aegypti. This review reveals that the essential oils are effective alternatives for the production of larvicides, which can be used in vector-borne disease control programmes.     

Chemical composition,Aedes mosquito larvicidal activity,and repellent activity against Triatoma rubrofasciata of Severinia monophylla leaf essential oil

Aedes aegypti and Ae. albopictus are key vectors in the spread of arboviruses such as dengue, chikungunya, yellow fever, and Zika. Triatoma rubrofasciata is an “assassin bug” whose populations and association with humans have dramatically increased and may represent a serious health concern. Control of insect vectors is a logical course of action to prevent the spread of these insect-borne infections. This work presents the leaf essential oil composition, mosquito larvicidal activities, and insect-repellent activity of Severinia monophylla. The essential oil of S. monophylla from Vietnam was obtained by hydrodistillation and analyzed by gas chromatography and mass spectrometry. The major components were sabinene, β-caryophyllene, bicyclogermacrene, germacrene D, (E)-nerolidol, globulol, and linalool. The leaf essential oil showed remarkable larvicidal activity against Ae. aegypti with LC₅₀ (48 h) of 7.1 μg/mL and Ae. albopictus with LC₅₀ (48 h) of 36 μg/mL. The essential oil also showed repellent activity on T. rubrofasciata at a concentration of 0.5%.

     

Chemical constituents and larvicidal potential of Feronia limonia leaf essential oil against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus

In the present investigation, the leaf essential oil of Feronia limonia was evaluated for chemical constituents and mosquito larvicidal activity against the larvae of Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus. GC and GC–MS analyses revealed that the essential oil contain 51 compounds. Estragole (34.69 %) and β-pinene(23.59 %) were identified as the major constituents followed by methyl (Z)-caryophyllene (11.05 %), eugenol (6.50 %), linalool (3.97 %), phytol (3.27 %), sabinene (2.41 %) and limonene (2.27 %). Larval mortality was observed after 12 and 24 h of exposure period. The oil showed remarkable larvicidal activity against A. stephensi (LC₅₀?=?38.93 and LC₉₀?=?108.64 ppm (after 12 h); LC₅₀?=?15.03 and LC₉₀?=?36.69 ppm (after 24 h)), A. aegypti (LC₅₀?=?37.60 and LC₉₀?=?104.69 ppm (after 12 h); LC₅₀?=?11.59 and LC₉₀?=?42.95 ppm (after 24 h)) and C. quinquefasciatus (LC₅₀?=?52.08 and LC₉₀?=?124.33 ppm (after 12 h); LC₅₀?=?22.49 and LC₉₀?=?60.90 ppm (after 24 h)). Based on the results, the essential oil of F. limonia can be considered as a new source of larvicide for the control of vector mosquitoes.     

Mosquitocidal essential oils: are they safe against non-target aquatic organisms?

In latest years, the importance of the Melaleuca alternifolia essential oil (EO) has been greatly empathised due to its anti-microbial and anti-inflammatory effects, as well as to its toxic properties towards many arthropods of great medical and veterinary importance. In this research, the EO extracted from aerial parts of M. alternifolia was evaluated for its toxicity against larvae of the most invasive mosquito worldwide, Aedes albopictus (Diptera: Culicidae), and towards adults of the water flea, Daphnia magna (Cladocera: Crustacea), a non-target aquatic organism that share the same ecological niche of A. albopictus. The chemical composition of M. alternifolia EO was investigated by GC-MS analysis. Tea tree EO was mainly composed by oxygenated monoterpenes, with 1,8-cineole as the major constituent. M. alternifolia EO exerted toxic activity against A. albopictus larvae, with a LC₅₀?=?267.130 ppm. However, this EO had a remarkable acute toxicity also towards adults of the non-target arthropod D. magna, with a LC₅₀?=?80.636 ppm. This research provide useful information for the development of newer and safer mosquito control tools, highlighting that the non-target effects against aquatic organisms that share the same ecological niche of A. albopictus larvae are crucial in the development of ecofriendly mosquito control strategies. Further research is needed to investigate the chronic and/or reproductive toxicity of M. alternifolia EO both towards target and non-target aquatic arthropods.     

Low-cost and eco-friendly green synthesis of silver nanoparticles using Feronia elephantum (Rutaceae) against Culex quinquefasciatus,Anopheles stephensi,and Aedes aegypti (Diptera: Culicidae)

Mosquitoes transmit serious human diseases, causing millions of deaths every year. The use of synthetic insecticides to control vector mosquitoes has caused physiological resistance and adverse environmental effects in addition to high operational cost. Insecticides of synthesized natural products for vector control have been a priority in this area. In the present study, the larvicidal activity of silver nanoparticles (AgNPs) synthesized using Feronia elephantum plant leaf extract against late third-instar larvae of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus was determined. The range of concentrations of synthesized AgNPs (5, 10, 15, 20, and 25 μg mL^?1) and aqueous leaf extract (25, 50, 75, 100, and 125 μg mL^?1) were tested against the larvae of A. stephensi, A. aegypti, and C. quinquefasciatus. Larvae were exposed to varying concentrations of aqueous crude extract and synthesized AgNPs for 24 h. Considerable mortality was evident after the treatment of F. elephantum for all three important vector mosquitoes. The synthesized AgNPs from F. elephantum were highly toxic than crude leaf aqueous extract to three important vector mosquito species. The results were recorded from UV–visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and energy-dispersive X-ray spectroscopy analysis (EDX). Synthesized AgNPs against the vector mosquitoes A. stephensi, A. aegypti, and C. quinquefasciatus had the following LC₅₀ and LC₉₀ values: A. stephensi had LC₅₀ and LC₉₀ values of 11.56 and 20.56 μg mL^?1; A. aegypti had LC₅₀ and LC₉₀ values of 13.13 and 23.12 μg mL^?1; and C. quinquefasciatus had LC₅₀ and LC₉₀ values of 14.19 and 24.30 μg mL^?1. No mortality was observed in the control. These results suggest that the green synthesis of silver nanoparticles using F. elephantum has the potential to be used as an ideal eco-friendly approach for the control of A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the mosquito larvicidal activity of the plant extracts and synthesized nanoparticles.     

Further insecticidal activities of essential oils from Lippia sidoides and Croton species against Aedes aegypti L.

This study assessed new insecticidal activities of essential oils from Lippia sidoides and Croton species (Croton zehntneri, Croton nepetaefolius, Croton argyrophylloides, and Croton sonderianus) against Aedes aegypti mosquito. In addition, the acute toxicity upon mice was determined. All essential oils showed inhibition of egg hatching, with IC₅₀ values ranging from 66.4 to 143.2 μg?mL^?1, larvicidal activity with LC₅₀ ranging from 25.5 to 94.6 μg?mL^?1, and pupicidal action with PC₅₀ ranging from 276.8 to over 500 μg?mL^?1. Only L. sidoides, C. zehntneri, and C. argyrophylloides essential oils were able to inhibit the oviposition of female gravid mosquitoes with OD₅₀ values of 35.3, 45.3, and 45.8 μg?mL^?1, respectively. Oral acute toxicity in mice showed that C. sonderianus and C. argyrophylloides oils are nontoxic (LD₅₀?>?6,000 mg.kg^?1) while C. nepetaefolius, C. zehntneri, and L. sidoides oils are moderately toxic (LD₅₀ 3,840; 3,464, and 2,624 mg.kg^?1, respectively). The results indicate that these oils are promising sources of bioactive compounds, showing low or no toxicity to mammals.     

Chemical composition and larvicidal activity of several essential oils from Hypericum species from Tunisia

The chemical composition of the essential oils extracted from some Tunisian Hypericum species and their larvicidal activity against Culex pipiens larvae were evaluated. The chemical compositions of the essential oils from the aerial plant parts were analyzed using gas chromatography–mass spectrometry. One hundred and thirty-four compounds were identified, ranging between 85.1 and 95.4 % of the oil's composition. The components were monoterpene hydrocarbons, oxygenated monoterpenes, sesquiterpene hydrocarbons, oxygenated sesquiterpenes, non-terpenic hydrocarbons, and others. The larvicidal activity of the essential oils was evaluated using a method recommended by WHO. Larvicidal tests revealed that essential oils from the Hypericum species have a significant larvicidal activity against C. pipiens, with LC₅₀ ranging between 102.82 and 194.70 ppm. The most powerful essential oils against these larvae were Hypericum tomentosum and Hypericum humifusum samples, followed by the essential oil of Hypericum perforatum.     

Citrus essential oils and four enantiomeric pinenes against Culex pipiens (Diptera: Culicidae)

The aim of this study was to evaluate the toxicity of pinenes (entantiomers of α- and β-) and essential oils from Greek plants of the Rutaceae family against the mosquito larvae of Culex pipiens (Diptera: Culicidae). Essential oils were isolated by hydrodistillation from fruit peel of orange (Citrus sinensis L.), lemon (Citrus limon L.), and bitter orange (Citrus aurantium L.). The chemical composition was determined by gas chromatography/mass spectrometry (GC/MS) analysis. Citrus essential oils contained in high proportion limonene and in lower quantities p-menthane molecules and pinenes. The insecticidal action of these essential oils and entantiomers of their pinenes on mosquito larvae was evaluated. Plant essential oils exhibited strong toxicity against larvae with the LC₅₀ values ranging from 30.1 (lemon) to 51.5 mg/L (orange) depending on Citrus species and their composition. Finally, the LC₅₀ value of pinenes ranging from 36.53 to 66.52 mg/L indicated an enantioselective toxicity only for the β-pinene entantiomer.     

Mosquito larvicidal properties of silver nanoparticles synthesized using Heliotropium indicum (Boraginaceae) against Aedes aegypti,Anopheles stephensi,and Culex quinquefasciatus (Diptera: Culicidae)

Mosquitoes transmit dreadful diseases to human beings wherein biological control of these vectors using plant-derived molecules would be an alternative to reduce mosquito population. In the present study activity of aqueous leaf extract and silver nanoparticles (AgNPs) synthesized using Helitropium indicum plant leaves against late third instar larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. The range of varying concentrations of synthesized AgNPs (8, 16, 24, 32, and 40 μg/mL) and aqueous leaf extract (30, 60, 90, 120, and 150 μg/mL) were tested against the larvae of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus. The synthesized AgNPs from H. indicum were highly toxic than crude leaf aqueous extract in three important vector mosquito species. The results were recorded from UV–Vis spectrum, Fourier transform infrared spectroscopy, scanning electron microscopy, energy-dispersive X-ray spectroscopy analysis, transmission electron microscopy, and histogram. The synthesized AgNPs showed larvicidal effects after 24 h of exposure. Considerable mortality was evident after the treatment of H. indicum for all three important vector mosquitoes. The LC₅₀ and LC₉₀ values of H. indicum aqueous leaf extract appeared to be effective against A. stephensi (LC₅₀, 68.73 μg/mL; LC₉₀, 121.07 μg/mL) followed by A. aegypti (LC₅₀, 72.72 μg/mL; LC₉₀, 126.86 μg/mL) and C. quinquefasciatus (LC₅₀, 78.74 μg/mL; LC₉₀, 134.39 μg/mL). Synthesized AgNPs against the vector mosquitoes of A. stephensi, A. aegypti, and C. quinquefasciatus had the following LC₅₀ and LC₉₀ values: A. stephensi had LC₅₀ and LC₉₀ values of 18.40 and 32.45 μg/mL, A. aegypti had LC₅₀ and LC₉₀ values of 20.10 and 35.97 μg/mL, and C. quinquefasciatus had LC₅₀ and LC₉₀ values of 21.84 and 38.10 μg/mL. No mortality was observed in the control. These results suggest that the leaf aqueous extracts of H. indicum and green synthesis of silver nanoparticles have the potential to be used as an ideal ecofriendly approach for the control of A. stephensi, A. aegypti, and C. quinquefasciatus. This is the first report on the mosquito larvicidal activity of the plant extracts and synthesized nanoparticles.     

Larvicidal and pupicidal activities of ecbolin A and ecbolin B isolated from Ecbolium viride (Forssk.) Alston against Culex quinquefasciatus Say (Diptera: Culicidae)

The mosquitocidal activity of different fractions and isolated compounds from the ethyl acetate extract of Ecbolium viride root was assessed on larvae and pupae of Culex quinquefasciatus Say (Diptera: Culicidae). The larvae and pupae were exposed to concentrations of 6.125, 12.5, 25 and 50 ppm for fractions and 1, 2.5, 5 and 10 ppm for compound. Among the 12 fractions screened, fraction 6 from the ethyl acetate extract of E. viride was recorded to have the highest larvicidal and pupicidal activities against C. quinquefasciatus. The lethal concentration (LC₅₀ and LC₉₀) values of fraction 6 were 4.26 and 9.0 ppm against C. quinquefasciatus larvae and 6.55 and 12.19 ppm against C. quinquefasciatus pupae, respectively, in 24 h. Fraction 7 was recorded to have moderate activity with LC₅₀ and LC₉₀ values of 11.25 and 25.02 ppm against C. quinquefasciatus larvae and 13.33 and 31.15 ppm against C. quinquefasciatus pupae, respectively, in 24 h. Ecbolin A and ecbolin B were identified from fractions 7 and 6, respectively. The structure of the isolated compounds was identified on the basis of spectral data (¹H NMR and ¹³C NMR) and compared with literature spectral data. Further, the isolated compound, ecbolin B, from fraction 6 was recorded to have strong larvicidal and pupicidal activities than ecbolin A. The LC₅₀ and LC₉₀ values of ecbolin B on C. quinquefasciatus larvae were 1.36 and 2.76 ppm, and on pupae, these were 1.54 and 3.51 ppm, respectively. The present results suggest that ecbolin B could be used as a mosquitocidal agent against C. quinquefasciatus.     

Bioactivity of essential oils of <Emphasis Type="BoldItalic">Zingiber officinalis</Emphasis> and <Emphasis Type="BoldItalic">Achyranthes aspera</Emphasis> against mosquitoes

Due to the global health problems associated with mosquito-borne diseases, over two million people primarily in the tropical countries are at risk. The widely and commonly used chemical method though effective, has some major disadvantages making insect control practically difficult. In view of the above, it is unavoidable to search for new molecules, which are eco-friendly, cheaper, and safer. The present study deals with evaluation of bioactive potential of two commonly occurring plants against mosquitoes presenting an alternative to the conventional chemical methods. Essential oils extracted by steam distillation from rhizome of Zingiber officinalis and leaf and stem of Achyranthes aspera were evaluated for larvicidal, attractant/repellent, and oviposition attractant/deterrent activity against two mosquito species viz. Aedes aegypti and Culex quinquefasciatus. The highest larvicidal activity, i.e., LC₅₀ = 154 ppm and LC₅₀ = 197 ppm for A. aegypti and C. quinquefasciatus, respectively was shown by Z. officinalis. This oil also offers 5-h protection at the concentration of 0.5 mg/cm2 from both mosquito species. The highest oviposition deterrence activity was exhibited by A. aspera stem oil, i.e., 100% and 85.71%, in case of A. aegypti and C. quinquefasciatus, respectively, at the concentration of 0.1%. These results reveal that both these oils have control potential against A. aegypti and C. quinquefasciatus.