Mosquito Larvicidal Properties Research Articles

Chemical characterization, antimicrobial and mosquito larvicidal activities of the essential oil of Camellia pleurocarpa (Gagnep.) Sealy from Vietnam

Camellia pleurocarpa (Gagnep.) Sealy, a species of yellow camellia indigenous to Vietnam, was investigated for its essential oil properties in this study. Hydrodistillation of its leaves yielded a complex mixture rich in sesquiterpenes and diterpenes. Chemical analysis identified 50 constituents, with notable compounds including spathulenol (13.26%), phytol (9.94%), and α-selinene (5.34%). The essential oil exhibited significant antimicrobial activity against three Gram-positive bacteria Enterococcus faecalis, Staphylococcus aureus, and Bacillus cereus; one Gram-negative bacterium Pseudomonas aeruginosa; and one yeast Candida albicans, with minimum inhibitory concentration (MIC) values ranging from 16 to 32 μg/mL and half-maximal inhibitory concentration (IC50) values ranging from 7.26 to 16.23 μg/mL. Furthermore, it demonstrated larvicidal potential against Aedes aegypti and Culex quinquefasciatus mosquitoes, with LC50 values ranging from 13.49 to 28.95 μg/mL and LC90 values ranging from 28.29 to 53.24 μg/mL. These findings underscore the promising antimicrobial and mosquito larvicidal properties of C. pleurocarpa essential oil, suggesting its potential as a natural alternative in combating microbial infections and controlling mosquito-borne diseases. This study represents the first comprehensive report on the chemical compositions and bioactivities of C. pleurocarpa essential oil.

Biocontrol efficacy of cajeput oil against Anopheles stephensi L. mosquito and its effect on non-target species.

Chemical insecticides are effective at controlling mosquito populations, but their excessive use can pollute the environment and harm non-target organisms. Mosquitoes can also develop resistance to these chemicals over time, which makes long-term mosquito control efforts challenging. In this study, we assessed the phytochemical, biochemical, and insecticidal properties of the chemical constituents of cajeput oil. Results show that Melaleuca cajuputi essential oil may exhibit mosquito larvicidal properties against Anopheles stephensi larvae (second-fourth instar) at 24h post-treatment. At 24h post-exposure, the essential oil resulted in a significant decrease in detoxifying enzymes. All of these findings indicate that cajeput oil infects An. stephensi larvae directly affect the immune system, leading to decreased immune function. Cajeput oil significantly affects the second, third, and fourth instar larvae of An. stephensi, according to the bioassay results. Cajeput oil does not induce toxicity in non-target Eudrilus eugeniae earthworm species, as indicated by a histological study of earthworms. Phytochemical screening and GC-MS analysis of the essential oil revealed the presence of several major phytochemicals that contribute to mosquito larvicidal activity. The importance of cajeput oil as an effective candidate for biological control of the malarial vector An. stephensi is supported by this study.

Biosynthesis of selenium nanoparticles using cell-free extract of Xenorhabdus cabanillasii GU480990 and their potential mosquito larvicidal properties against yellow fever mosquito Aedes aegypti

Nanomaterials are successful due to their numerous applications in various domains such as cancer treatment, environmental applications, drug and gene delivery. Selenium is a metalloid element with broad biological activities and low toxicity especially at the nanoscale. Several studies have shown that nanoparticles synthesized from microbial and plant extracts are effective against important pests and pathogens. This study describes the bio fabrication of selenium nanoparticles using cell free extract of Xenorhabdus cabanillasii (XC-SeNPs) and assessed their mosquito larvicidal properties. Crystallographic structure and size of XC-SeNPs were determined with UV-a spectrophotometer, Fourier-transform infrared spectroscopy (FTIR), X-ray diffraction analysis (XRD), Energy-dispersive X-ray spectroscopy (EDAX), Zeta potential and Transmission electron microscopy (TEM). The significant surface plasmon resonance at 275 nm indicated the synthesis of XC-SeNPs from the pure cell-free extract of X. cabanillasii. The XRD result exhibits the crystalline nature of XC-SeNPs. The Zeta potential analysis confirmed that the surface charge of XC-SeNPs was −24.17 mV. TEM analysis revealed that synthesized XC-SeNPs were monodispersed, spherically shaped, and sized about 80–200 nm range. In addition, the larvicidal potentials of the bio-fabricated XC-SeNPs were assessed against the 4th-instar Ae. aegypti. XC-SeNPs displayed a dose-dependent larvicidal effect; the larval mortality was 13.3 % at the minimum evaluated concentration and increased to 72 % at higher dose treatments. The LC50 and LC90 concentration of XC-SeNPs against mosquito larvae were 79.4 and 722.4 ppm, respectively.

Selective Partition of Lipopeptides from Fermentation Broth: A Green and Sustainable Approach.

Lipopeptide (LP) biosurfactants from microbes have the potential to gradually replace chemical synthetic surfactants and fit the contemporary green and sustainable industrial production concept. However, their active participation is comparatively low in the global market pertaining to their low yield in microbial broth and costly downstream processes arising due to tedious isolation and purification methods. Herein, an efficient extraction method is developed that utilizes an aqueous biphasic system (ABS) comprising ionic liquids and polypropylene glycol 400 (PPG) to selectively extract a mixture of cyclic lipopeptides, namely, surfactin and fengycin from the culture broth of Bacillus amyloliquefaciens 5NPA-1, isolated from the halophyte Salicornia brachiata Roxb. Out of four different ABSs, the ABS composed of 2-hydroxyethyl ammonium formate and PPG displayed a maximum extraction efficiency of 82.30%. PPG-rich phase containing lipopeptides exhibited excellent antimicrobial and mosquito larvicidal properties with no toxic effect on plants. The developed method is simple, novel and accelerates the application of cyclic lipopeptides produced by the microbial source.

Lantana camara L. essential oil mediated nano-emulsion formulation for biocontrol application: anti-mosquitocidal, anti-microbial and antioxidant assay.

Mosquitoes play an important role in the spread of vector-borne diseases and their management is highly essential. Plant extracts have been explored for their mosquitocidal activity against different types of vectors. The present work aimed to determine the larvicidal and pupicidal activity of Lantana camara L. essential oil-loaded nano-emulsion formulation for the control of pests. The synthesized essential oil-loaded nano-emulsion was subjected to evaluate the antioxidant potential and mosquito larvicidal properties. GC-MS analysis revealed that the essential oil of Lantana camara L. leaf contained 12 bioactive components. Caryophyllene oxide (15.81), n-Hexadecanoic acid (4.22), Davanone (6.49) and beta-Sesquiphellandrene (2.32) are the major compounds identified. The nano-emulsion was effective against A. aegypti immature stage (larvae and pupae) and adult mosquitoes in laboratory conditions. The LC50 was found to be 18.183ppm (I), 23.337ppm (II), 29.731ppm (III), 38.943ppm (IV) instars and 45.295ppm (pupae), respectively. The LD50 and LD90 values for adult mosquitoes were 11.947mg/cm2 and 47.716mg/cm2, respectively. The antioxidant activity of ascorbic acid (55.9%), glutathione (67.7%) and quercetin (48.6%) was recorded, respectively. The level of acetylcholinesterase (0.06mM) and alkaline phosphatase (0.05mM) activity significantly decreased from the control (0.12mM) which revealed the efficacy of essential oil-loaded nano-emulsion to treat larvae. This study suggested that using an essential oil-loaded nano-emulsion formulation effectively controlled the mosquito vectors. It was also evidenced that the use of nano-emulsion has a great role in near future, especially in vector management.

Phytochemical and Pharmacological Evaluation of Methanolic Extract of Knoxia sumatrensis Leaves

ABSTRACT Knoxia sumatrensis leaf extracts in methanol were analyzed for the phytochemical compositions, antioxidant properties (DPPH, ABTS, and hydroxyl radical assay), anti-proliferative activity (lung cancer A549 and breast cancer MCF-7 cell lines), and mosquito larvicidal properties. The GC-MS analysis showed the presence of eight bioactive compounds of which the hexadecanoic Acid, 2-Propyl-, methyl Ester, and 2,3-anhydro-D-Mannosan were the two major compounds present. The bioactive compounds present included phenolics and flavonoids (55.0 ± 1.3 mg GAE g−1 d.w. and 42.5 ± 0.5 mg RE g−1 d.w.). FT-IR analysis detected the presence of aldehydes and anhydrites functional groups. Antioxidant properties were positively associated with the secondary metabolites. The anti-proliferative activity of methanolic leaf extracts showed the IC50 values 135.82 and 181.73 μg mL−1 for A549 and MCF-7, respectively. The methanolic extract also showed larvicidal activity on three mosquito species with highest toxicity on Culex quinquefasciatus larvae with LC50 4.84 mg mL−1 and LC90 19.33 mg mL−1.

Essential Oil Compositions of Three Invasive Conyza Species Collected in Vietnam and Their Larvicidal Activities against Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus.

Mosquito-borne infectious diseases are a persistent problem in tropical regions of the world, including Southeast Asia. Vector control has relied principally on synthetic insecticides, but these have detrimental environmental effects and there is an increasing demand for plant-based agents to control insect pests. Invasive weedy plant species may be able to serve as readily available sources of essential oils, some of which may be useful as larvicidal agents for control of mosquito populations. We hypothesize that members of the genus Conyza (Asteraceae) may produce essential oils that may have mosquito larvicidal properties. The essential oils from the aerial parts of Conyza bonariensis, C. canadensis, and C. sumatrensis were obtained by hydrodistillation, analyzed by gas chromatography–mass spectrometry, and screened for mosquito larvicidal activity against Aedes aegypti, Ae. albopictus and Culex quinquefasciatus. The essential oils of C. canadensis and C. sumatrensis, both rich in limonene (41.5% and 25.5%, respectively), showed notable larvicidal activities against Ae. aegypti (24-h LC50 = 9.80 and 21.7 μg/mL, respectively) and Ae. albopictus (24-h LC50 = 18.0 and 19.1 μg/mL, respectively). These two Conyza species may, therefore, serve as sources for alternative, environmentally-benign larvicidal control agents.

Isolation and growth inhibition potential of entomopathogenic nematodes against three public health important mosquito vectors

The prevalence of mosquito vector borne diseases and the resistance of mosquitoes to conventional pesticides have been of important public concern to the mosquito endemic countries. Present study was conducted to identify the native bio-larvicidal potential of the entomopathogenic nematodes; Steinernema siamkayai (KPR-4) Heterohabditis indica (KPR-8), Steinernema glaseri and Steinernema abbasi. The isolated nematodes were subsequently cultured and evaluated their larvicidal potential against the larvae of Aedes aegypti, Anopheles stephensi and Culex quinquefasciatus. Among the tested four different nematode species, the S. abassi exerted the highest mortality against A. aegypti (97.33%), the H. indica (KPR-8) against A. stephensi (97.33%) and the S. siamkayai (KPR-4) against C. quinquefasciatus (98.67%). The maximal mosquito-larvicidal property of EPNs was found with the LC50 and LC90 values (IJs/larvae): S. abbasi = 12.47 & 54.35 on A. aegypti; H. indica KPR-8 = 19.88 & 66.81 on A. stephensi and S. siamkayai KPR-4 = 16.69 & 58.97 on C. quinquefasciatus, respectively. The presently generated data on the molecular and larvicidal characteristics of the entomopathogenic nematodes form an important baseline data that upon further research would lead to the development of eco-friendly mosquito-control agent.

Pharmacological and Larvicidal Potential of Green Synthesized Silver Nanoparticles Using Carmona retusa (Vahl) Masam Leaf Extract

Mosquito control is facing a challenge worldwide, due to ineffectiveness of chemical insecticides. Identification of novel and ecofriendly insecticides is the need of the hour. In the present study mosquito control efficacy, antioxidants and anti-cancerous potential of silver nanoparticle conjugated with Carmona retusa (Vahl) Masam nanoparticles. Synthesized nanoparticles had UV absorption maximum at 420 nm, size ranging between 20 and 40 nm based of TEM, has cubic structure, C–H bending and Ag Metal bands. Results show high free radical scavenging ability of C. retusa derived silver nanoparticles as evidenced by DPPH radical and H2O2 radical assay. C. retusa derived nanoparticles produce 80% inhibition in MCF-7 cell line at concentration of 500 μg/ml. High larvicidal activity with LC50 values of 116.681 ppm for Anopheles stephensi, 198.766 ppm for Aedes aegypti, and 83.553 ppm for Culex quinquefasciatus were observed. Based on the findings of the study we suggest that C. retusa plant mediated AgNPs has anticancerous and mosquito larvicidal property and could be bioprospected for drug development and mosquito control.

Molecular Characterization of Mosquitocidal Toxin (Surface Layer Protein, SLP) from Bacillus cereus VCRC B540.

A marine Bacillus cereus (VCRC B540) with mosquitocidal effect was recently reported from red snapper fish (Lutjanus sanguineous) gut and surface layer protein (S-layer protein, SLP) was reported to be mosquito larvicidal factor. In this present study, the gene encoding the surface layer protein was amplified from the genomic DNA and functionally characterized. Amplification of SLP-encoding gene revealed 1,518bp PCR product, and analysis of the sequence revealed the presence of 1482bp open reading frame with coding capacity for a polypeptide of 493 amino acids. Phylogenetic analysis revealed with homology among closely related Bacillus cereus groups of organisms as well as Bacillus strains. Removal of nucleotides encoding signaling peptide revealed the functional cloning fragment of length 1398bp. Theoretical molecular weight (51.7kDa) and isoelectric point (5.99) of the deduced functional SLP protein were predicted using ProtParam. The amplified PCR product was cloned into a plasmid vector (pGEM-T), and the open reading frame free off signaling peptide was subsequently cloned inpET-28a(+) and expressed in Escherichia coli BL21 (DE3). The isopropyl-β-D-thiogalactopyranoside (IPTG)-induced recombinant SLP was confirmed using western blotting, and functional SLP revealed mosquito larvicidal property. Therefore, the major findings revealed that SLP is a factor responsible for mosquitocidal activity, and the molecular characterization of this toxin was extensively studied.

Mosquito-larvicidal efficacy of gold nanoparticles synthesized from the seaweed, Turbinaria ornata (Turner) J.Agardh 1848

ABSTRACTMalaria is considered a dreadful mosquito-borne infectious disease of human beings caused and spread by biting of the female mosquito Anopheles stephensi infected with a parasitic protozoan Plasmodium falciparum. Continuous application of chemicals/synthetic insecticides for vector control causes various problems such as resistant mechanism of mosquito, toxicity to nontarget aquatic organisms and disturbance to the microbial community of the soil. Currently, green synthesized nanoparticles are being employed in various biological processes including insect and pest control. The present investigation focused on the mosquito-larvicidal property of Turbinaria ornata-mediated gold nanoparticles (To-AuNPs) and its boiled aqueous extract (To-AE) against the malarial vector A. stephensi. The recorded lethal concentration (LC50 and LC90) values (µg/ml) of To-AE and To-AuNPs against fourth instar larvae of A. stephensi were 37.77 and 159.55 and 12.79 and 78.70, respectively. The To-AuNPs were characterized through UV-visible spectroscopy, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD), field emission scanning electron microscopy (FESEM), high-resolution transmission electron microscopy (HRTEM), energy dispersive x-ray spectroscopy (EDX), zeta potential and dynamic light scattering (DLS) method. The presently synthesized gold nanoparticles through the single-step, eco-friendly method is a potentially effective mosquitocidal agent.

Isolation and molecular characterization of actinomycetes with antimicrobial and mosquito larvicidal properties

The present study aimed to isolate actinomycetes from soil samples collected from Western Ghats regions, Tamil Nadu, India. Totally 400 actinomycetes isolates were isolated, of which 161 (40.2%) showed antimicrobial activity in preliminary screening. Secondary screening yielded 27 active isolates; twelve of them showed good antimicrobial and larvicidal activities. Five isolates namely S12-4, S12-17, S12-8, DPS-14 and FMS-20 presented 98%, 93%, 87%, 82%, and 80% larvicidal activity against Cx. quinquefasciatus; very low larvicidal activity was observed against Ae. aegypti. S12-4 showed 100% larval mortality against An. stephensi. RAPD results showed highest similarity between DPS-122 and KFS-24 (0.89246). The polymorphic index observed in the primers ranged from 0.286 (OPA-09) to 0.07 (OPC-18). The results suggest that Western Ghats regions may be a good natural source for isolation of actinobacteria and thereby for discovering novel molecules with antimicrobial and mosquito larvicidal properties.

Chemical Composition and Mosquito Larvicidal Properties of Essential Oil from Leaves of an Iranian Indigenous Plant Zhumeria majdae

The use of natural products derived from plants in mosquitoes control is an alternative method for minimizing the side effects of chemical pesticides on the environment. In the current study chemical composition of essential oil extracted from an indigenous plant, Zhumeria majdae was determined and identified by gas chromatography (GC) and GC-mass spectrometry (MS) analysis. In addition, the larvicidal activity of essential oil was evaluated against two important mosquito vectors, Anopheles stephensi and Culex quinquefasciatus. Thirty constituents, representing 97.86 % of the oil, were identified. The main constituents of the oil were camphor (38.84 %), linalool (31.18 %) and camphene (7.73 %). Z. Majdae volatile oil showed significant toxicity against larvae of both species. The LC50 and LC90 values against An. stephensi larvae were 61.34 and 135.81 ppm and for Cx. quinquefasciatus were 88.51 and 191.56 ppm after 24 hours, respectively. Our findings indicated that the essential oil from Z. majdae leaves may be explored as a potential mosquito bio-larvicide.

Structural characterization and evaluation of mosquito-larvicidal property of silver nanoparticles synthesized from the seaweed, Turbinaria ornata (Turner) J. Agardh 1848

The silver nanoparticles synthesized from Turbinaria ornata (To-AgNPs) showed spherical with crystalline nature (20–32 nm) was evaluated against fourth instar larvae of three mosquitoes. The maximum activity of To-AgNPs was recorded on Aedes aegypti followed by Anopheles stephensi and Culex quinquefasciatus with the following lethal concentration values (μg/ml): LC50 of 0.738, 1.134, and 1.494; and LC90 of 3.342, 17.982, and 22.475, respectively. The obtained respective values (μg/ml) vis-a-vis aqueous extract (To-AE) were: 2.767 and 40.577; 4.347 and 158.399, and 7.351 and 278.994. The findings revealed that To-AgNPs could form a base for the development of an eco-friendly, low-cost pesticide.

Evaluation of Mosquito Repellent Activity of Isolated Oleic Acid, Eicosyl Ester from Thalictrum javanicum.

To evaluate the traditional use, the mosquito repellent property of Thalictrum javanicum and to confirm the predicted larvicidal activity of the isolated compound, oleic acid, eicosyl ester from its aerial parts by PASS software, the present study was carried out using 4th instar stage larvae of the mosquitoes, Aedes aegypti (dengue vector) and Culex quinquefasciatus (filarial vector). Insecticidal susceptibility tests were conducted and the mortality rate was observed after 24 h exposure. The chitinase activity of isolated compound was assessed by using purified β-N-acetyl glucosaminidase (chitinase). Ecdysone 20-monooxygenase assay (radioimmuno assay) was made using the same larval stage of A. aegyptiand C. quinquefasciatus. The results were compared with the crude methanol extract of the whole plant. The isolated compound, oleic acid, eicosyl ester was found to be the most effective larvicide against A. aegypti (LC50/24 h -8.51 ppm) and C. quinquefasciatus (LC50/24 h - 12.5 ppm) than the crude methanol extract (LC50/24 h - 257.03 ppm and LC50/24 h - 281.83 ppm, respectively). The impact of oleic acid, eicosyl ester on reducing the activity of chitinase and ecdysone 20-monooxygenase was most prominent in both the target species, A. aegyptiand C. quinquefasciatus than the control. The results therefore suggest that the compound, oleic acid, eicosyl ester from Thalictrum javanicum may be considered as a potent source of mosquito larvicidal property.

Biosynthesis of silver nanoparticles from mangrove plant (Avicennia marina) extract and their potential mosquito larvicidal property.

To identify the larvicidal activities of silver nanoparticles synthesised with Avicennia marina leaf extract against the larvae of Aedes aegypti and Anopheleus stephensi, in vitro larvicidal activities such as LC50 and LC90 were assessed. Further, characterisation such as UV and FTIR analysis were carried out for the synthesised silver nanoparticles. The LC50 value of the synthesised silver nanoparticles was identified as 4.374 and 7.406mg/L for An. stephensi and Ae. aegypti larvae respectively. Further, the LC90 values are also identified as 4.928 and 9.865mg/L for An. stephensi and Ae. aegypti species respectively. The synthesised silver nanoparticles have maximum absorption at 420nm with the average size of 60-95nm. The FTIR data showed prominent peaks in (3940.57, 3929.00, 3803.63, 3712.97, 2918.30, 2231.64, 1610.50, 1377.17, 1257.59, 1041.59, 1041.56, 775.38, 667.37 and 503.21) different ranges. The biosynthesis of silver nanoparticles with leaf aqueous extract of A. marina provides potential source for the larvicidal activity against mosquito borne diseases. The present study proved the mosquitocidal properties of silver nanoparticles synthesised from mangroves of Vellar estuary. This is an ideal eco-friendly approach for the vector control programs.

Synthesis of some novel phosphorylated and thiophosphorylated benzimidazoles and benzothiazoles and their evaluation for larvicidal potential to Aedes albopictus and Culex quinquefasciatus

Series of benzimidazole and benzothiazole linked phosphoramidates and phosphoramidothioates (5a–j) and benzimidazole linked phenylphosphoramidates and phenylphosphoramidothioates (10a–e) were synthesized. The title compounds were preliminary screened for mosquito larvicidal properties against Aedes albopictus and Culex quinquefasciatus at different concentration from 40 to 5mg/L. Among the screened compounds three compounds revealed potential larvicidal effects with 100% mortality in the order of 10e>5j>5e. Compound 10e was found to be the most toxic compound to Ae. albopictus and Cx. quinquefasciatus. The LC50 of 10e against Ae. albopictus was found to be 6.42 and 5.25mg/L at 24 and 48h, respectively, whereas it was 7.01 and 3.88mg/L, respectively in Cx. quinquefasciatus. Temephos was used as positive control.

Mosquito larvicidal activity of seaweeds extracts against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus

ObjectiveTo identify the larvicidal activity of the seaweed extracts against Anopheles stephensi, Aedes aegypti and Culex quinquefasciatus MethodsSeaweed extracts of Ulva lactuca, Caulerpa racemosa (C. racemosa), Sargassum microystum, Caulerpa scalpelliformis, Gracilaria corticata, Turbinaria decurrens, Turbinaria conoides and Caulerpa toxifolia were dissolved in DMSO to prepare a graded series of concentration. The test for the larvicidal effect of seaweeds against mosquitos larvae was conducted in accordance with the WHO standard method. Batches of 25 early 4th instar larvae of three mosquitoes were transferred to 250 mL enamel bowl containing 199 mL of distilled water and 1 mL of plant extracts (10–100 μg). Each experiment was conducted with triplicate with concurrent a control group. ResultsAmong the seaweeds extract, C. racemosa showed toxicity against 4th instar larvae of Aedes aegypti, Culex quinquefasciatus, Anopheles stephensi with equivalent LC 50 value (0.055 6±0.010 3) μg/mL, (0.067 5±0.136 0) μg/mL and (0.066 1±0.007 6) μg/mL, respectively. ConclusionsThe present study concluded that, the mosquito larvicidal property of C. racemosa might be the prospective alternative source to control the mosquitoes.

Biosynthesis of silver nanoparticles by using mangrove plant extract and their potential mosquito larvicidal property

Objective To identify the larvicidal activities of silver nano particles synthesised with Rhizophora mucronata ( R. mucronata) leaf extract against the larvae of Aedes aegypti (Ae. aegypti) and Culex quinquefasciatus (Cx. quinquefasciatus). Methods In vitro larvicidal activities such as LC 50 and LC 90 were assessed for the Ae. aegypti and Cx. quinquefasciatus larval species. Further, characterisation such as UV, XRD, FTIR and AFM analysis were carried out for the synthesised silver nano particles. Results The LC 50 value of the synthesised silver nano particle was identified as 0.585 and 0.891 mg/L for Ae. aegypti and Cx. quinquefasciatus larvae respectively. Further, the LC 90 values are also identified as 2.615 and 6.291 mg/L for Ae. aegypti and Cx. quinquefasciatus species respectively. The synthesised silver nanoparticles have maximum absorption at 420 nm with the average size of 60-95 nm. The XRD data showed 2θ intense values with various degrees such as 37.10°, 47.66°, 63.97° and 70.01°. The FTIR data showed prominent peaks in (3 426.89, 2 925.49, 2 869.56, 2 346.95, 1 631.49, 1 031.73, 669.18 and 455.12) different ranges. Conclusions The biosynthesis of silver nanoparticles with leaf aqueous extract of R. mucronata provides potential source for the larvicidal activity against mosquito borne diseases.

Insecticidal activity of essential oil from Chamaecyparis formosensis Matsum

Abstract Chamaecyparis formosensis is an endemic precious tree species grown in Taiwan. Based on the results obtained in our current study, the essential oil of C. formosensis wood possesses significant insecticidal activities. In an assay to assess mosquito larvicidal properties, the essential oil completely killed the larvae of Aedes aegypti and Aedes albopictus at a dosage of 100 μg ml-1 in water. Concentrations of the essential oil at a dosage of 0.16 mg cm-3 in air resulted in 100% mortality of silverfish after 2 h. It was found that the extractives of C. formosensis possess multiple bioactivities against insects. There is great potential for the development of insecticides for domestic application to kill mosquito larvae and silverfish based on this raw material.