Toxicity of Ulva lactuca and green fabricated silver nanoparticles against mosquito vectors and their impact on the genomic DNA of the dengue vector Aedes aegypti.

Marine seaweeds are known to have a potential role against microbial and pesticidal activities. Ulva lactuca, a green macroalgae extract analysed through gas chromatography mass spectrometry reveals 31 compounds. Resistance of mosquito vectors to synthetic insecticides remains a major problem. Discovering and applying natural agents to act against disease vectors is challenging. The activities of the extract and nano-fabricated green synthesised silver nanoparticles were checked for use against Aedes aegypti and Culex pipiens. The crude extract and synthesised silver nanoparticles exhibited a notable larvicidal effect, and very effective inhibition of pupal and adult emergence. Inhibition of adult emergence of Ae.aegypti was 97.7% and in Cu.pipiens, it was 93.3%. Our genotypic study of Deoxyribonucleic acid from treated larvae utilising random primers MA-09, MA-12 and MA-26 revealed damaged nucleotide sequences when compared with the controls. The antimicrobial activity of both the extract and green synthesised nanomaterials showed prominent activity against pathogenic drug resistant bacteria. Our results contribute to further development of eco-friendly insecticides with lower cost of preparation. This could further contribute to further research helping future generations to be free from these deadly disease-causing vectors and pathogenic microbes.

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

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

Phytochemistry, Ethnopharmacological Uses, Biological Activities, and Therapeutic Applications of Cassia obtusifolia L.: A Comprehensive Review.

Cassia obtusifolia L., of the Leguminosae family, is used as a diuretic, laxative, tonic, purgative, and natural remedy for treating headache, dizziness, constipation, tophobia, and lacrimation and for improving eyesight. It is commonly used in tea in Korea. Various anthraquinone derivatives make up its main chemical constituents: emodin, chrysophanol, physcion, obtusifolin, obtusin, au rantio-obtusin, chryso-obtusin, alaternin, questin, aloe-emodin, gluco-aurantio-obtusin, gluco-obtusifolin, naphthopyrone glycosides, toralactone-9-ß-gentiobioside, toralactone gentiobioside, and cassiaside. C. obtusifolia L. possesses a wide range of pharmacological properties (e.g., antidiabetic, antimicrobial, anti-inflammatory, hepatoprotective, and neuroprotective properties) and may be used to treat Alzheimer's disease, Parkinson's disease, and cancer. In addition, C. obtusifolia L. contributes to histamine release and antiplatelet aggregation. This review summarizes the botanical, phytochemical, and pharmacological features of C. obtusifolia and its therapeutic uses.

Bioefficacy of Epaltes divaricata (L.) n-Hexane Extracts and Their Major Metabolites against the Lepidopteran Pests Spodoptera litura (fab.) and Dengue Mosquito Aedes aegypti (Linn.).

The present research investigated the chemical characterization and insecticidal activity of n-Hexane extracts of Epaltes divaricata (NH-EDx) along with their chief derivatives n-Hexadecanoic acid (n-HDa) and n-Octadecanoic acid (n-ODa) against the dengue vector Aedes aegypti and lepidopteran pest Spodoptera litura. Chemical screening of NH-EDx through GC-MS analysis delivered nine major derivatives, and the maximum peak area percentage was observed in n-Hexadecanoic acid (14.63%) followed by n-Octadecadienoic acid (6.73%). The larvicidal activity of NH-EDx (1000 ppm), n-HDa (5 ppm), and n-ODa (5 ppm) against the A. aegypti and S. litura larvae showed significant mortality rate in a dose-dependent way across all the instars. The larvicidal activity was profound in the A. aegypti as compared to the S. litura across all the larval instars. The sublethal dosages of NH-EDx (500 ppm), n-HDa (2.5 ppm), and n-ODa (2.5 ppm) also showed alterations in the larval/pupal durations and adult longevity in both the insect pests. The enzyme activity revealed that the α- and ß-carboxylesterase levels were decreased significantly in both the insect pests, whereas the levels of GST and CYP450 uplifted in a dose-dependent manner of NH-EDx, n-HDa, and n-ODa. Correspondingly, midgut tissues such as the epithelial layer (EL), gut lumen (GL), peritrophic matrix (Pm), and brush border membrane (BBM) were significantly altered in their morphology across both A. aegypti and S. litura against the NH-EDx and their bioactive metabolites. NH-EDx and their bioactive metabolites n-HDa and n-ODa showed significant larvicidal, growth retardant, enzyme inhibition, and midgut toxicity effects against two crucial agriculturally and medically challenging insect pest of ecological importance.

Root exudate chemical cues of an invasive plant modulate oviposition behavior and survivorship of a malaria mosquito vector.

Gravid female Anopheles gambiae mosquitoes identify suitable oviposition sites through a repertoire of cues, but the influence of allelochemicals, especially root phytochemicals in modulating this behavior and impacting subsequent progeny bionomics remains unexplored. We addressed these questions in the malaria vector Anopheles gambiae and its invasive host plant Parthenium hysterophorus. Using chemical analysis combined with laboratory behavioral assays, we demonstrate that a blend of terpenes, namely α-pinene, α-phellandrene, ß-phellandrene, 3-carene and (E)-caryophyllene emitted from P. hysterophorus root exudate treated-water attracted gravid females. However, fewer eggs (55%) hatched in this treatment than in control water (66%). The sesquiterpene lactone parthenin, identified in both the natural aquatic habitat harboring P. hysterophorus and root exudate-treated water was found to be responsible for the ovicidal effect. Moreover, larvae exposed to parthenin developed 2 to 3 days earlier but survived 4 to 5 days longer as adults (median larval survival time = 9 days (all replicates);11 to 12 days as adults) than the non-exposed control (median larval survival time = 11 days (reps 1 & 2), 12 days (rep 3); 6 to 7 days as adults). These results improve our understanding of the risk and benefits of oviposition site selection by gravid An. gambiae females and the role root exudate allelochemicals could play on anopheline bionomics, with potential implications in malaria transmission.

An evaluation of repellency and feeding inhibition of ethno-medicinal plants against major malaria vectors in southern Ethiopia.

BACKGROUND: Plant-based mosquito control methods may use as a supplementary malaria vector control strategy. This study aimed to evaluate the effect of smoking ethno-medicinal plants on indoor density and feeding activity of malaria vectors at early hours of the night and its residual effect after midnight in southern Ethiopia. METHODS: Both field and tent trials were conducted to evaluate the impact of smoking Juniperus procera leaves, Eucalyptus globulus seeds and Olea europaea leaves in Kolla Shara Village from July 2016 to February 2017. For the field trial, five grass-thatched traditional huts (three for ethno-medicinal plants and two as control [only charcoal smoking and non-charcoal smoking]) were used. Indoor host-seeking mosquitoes were collected by CDC light traps. A Latin square design was employed to minimize the bias due to the variation in house location and different sampling nights. For the tent experiment, 25 3-5-day-old starved wild female Anopheles mosquitoes reared from the larvae were released into the tents where a calf was tethered at the mid-point of each tent. RESULTS: A total of 614 Anopheles mosquitoes belonging to 5 species were collected from 5 huts, of which 93.4% was An. arabiensis; O. europaea, E. globulus and J. procera reduced the indoor density of An. arabiensis, with the mean percentage drop of 80%, 73% and 70%, respectively. In the tent trial, smoking of these plants had significant knockdown effects and inhibited feeding on the calves (F = 383.5, DF = 3, P < 0.01). The mean knockdown effect due to O. europaea was relatively high (17.7 ± 0.54; 95% CI 16.8-18.6), while it was only 0.9 ± 0.1 (95% CI 0.29-1.52) in the control tents. All the test plants used in the tent trial caused significantly inhibited feeding activity of An. arabiensis on the host (F = 383.5, DF = 3, P < 0.01). About 94.5%, 89.5% and 86% of mosquitoes were unfed because of the smoking effect of O. europaea, E. globulus and J. procera, respectively, whereas only 19.5% were unfed in the control tent. CONCLUSIONS: Smoking ethno-medicinal plant materials reduced indoor density of malaria vectors and inhibited feeding on calves inside the tents. Thus, plant-based mosquito control methods may play a vital role in reducing mosquito bites in the early hours of the night and thereby reduce residual malaria transmission.

Lantana camara Essential Oils from Vietnam: Chemical Composition, Molluscicidal, and Mosquito Larvicidal Activity.

Lantana camara is a troublesome invasive plant introduced to many tropical regions, including Southeast Asia. However, the plant does hold promise as a source of essential oils that may be explored for potential use. Fresh water snails such as Pomacea canaliculata, Gyraulus convexiusculus, and Tarebia granifera can be problematic agricultural pests as well as hosts for parasitic worms. Aedes and Culex mosquitoes are notorious vectors of numerous viral pathogens. Control of these vectors is of utmost importance. In this work, the essential oil compositions, molluscicidal, and mosquito larvicidal activities of four collections of L. camara from north-central Vietnam have been investigated. The sesquiterpene-rich L. camara essential oils showed wide variation in their compositions, not only compared to essential oils from other geographical locations (at least six possible chemotypes), but also between the four samples from Vietnam. L. camara essential oils showed molluscicidal activities comparable to the positive control, tea saponin, as well as other botanical agents. The median lethal concentrations (LC50 ) against the snails were 23.6-40.2 µg/mL (P. canaliculata), 7.9-29.6 µg/mL (G. convexiusculus), and 15.0-29.6 µg/mL (T. granifera). The essential oils showed good mosquito larvicidal activities with 24-h LC50 values of 15.1-29.0 µg/mL, 26.4-53.8 µg/mL, and 20.8-59.3 µg/mL against Ae. aegypti, Ae. albopictus, and Cx. quinquefasciatus, respectively. The essential oils were more toxic to snails and mosquito larvae than they were to the non-target water bug, Diplonychus rusticus (24-h LC50 =103.7-162.5 µg/mL). Sesquiterpene components of the essential oils may be acting as acetylcholinesterase (AChE) inhibitors. These results suggest that the invasive plant, L. camara, may be a renewable botanical pesticidal agent.

Molecular characterization, gas chromatography mass spectrometry analysis, phytochemical screening and insecticidal activities of ethanol extract of Lentinus squarrosulus against Aedes aegypti (Linnaeus).

Mosquito-transmitted diseases like zika, dengue, chikungunya, and yellow fever are known to affect human health worldwide. Numerous synthetic insecticides have been used as vector control for these diseases, but there is the challenge of environmental toxicity and vector resistance. This study investigated the medicinal and insecticidal potential of Lentinus squarrosulus against Aedes aegypti. The fruiting bodies were identified morphologically as well as using internal transcribed spacer (ITS) sequences for its molecular characterization. Genomic deoxyribonucleic acid (DNA) yield was confirmed with NanoDrop Spectrophotometer ND-1000 and amplified with ITSl and ITS4 primers. The amplicons were sequenced and the National Center for Biotechnology Information (NCBI) database identified the nucleotides. Its ethanol extract was subjected to phytochemical screening and gas chromatography mass spectrometry (GC-MS) analysis and tested against the pupa and fourth instar larva of Aedes aegypti with percentage mortality monitored. The Macrofungus was identified morphologically and confirmed with molecular characterization as Lentinus squarrosulus (LS). The gene sequence was deposited in GenBank (Accession number MK629662.1). GC-MS analysis showed that its ethanol extract has 25 bioactive compounds with 9,12-Octadecadienoic acid, ethyl ester having the highest percentage of 43.32% as well as methyl-2-oxo-1-pyrrolidine acetate and 17-octadecynoic acid having the lowest percentage (0.09%). The macrofungus contained varied concentrations of phytochemicals including phenols (159 mg/g GAE), tannins (1.6 mg/g TAE), and flavonoids (31.4 mg/g QE). The ethanol extract had significant potent effects on Aedes aegypti larva and pupa which could be due to the occurrence and abundance of 9,12-octadecadienoic acid in LS. The LC50 of the extract for larvicidal and pupicidal activities were 2.95 mg/mL and 3.55 mg/mL, respectively, while its LC90 were 6.31 mg/mL and 5.75 mg/mL respectively. Lentinus squarrosulus had insecticidal effects against the Aedes aegypti larva and pupa and possessed great potential as a source of alternative medicine and eco-friendly insecticides.

Evaluating putative repellent 'push' and attractive 'pull' components for manipulating the odour orientation of host-seeking malaria vectors in the peri-domestic space.

BACKGROUND: Novel malaria vector control approaches aim to combine tools for maximum protection. This study aimed to evaluate novel and re-evaluate existing putative repellent 'push' and attractive 'pull' components for manipulating the odour orientation of malaria vectors in the peri-domestic space. METHODS: Anopheles arabiensis outdoor human landing catches and trap comparisons were implemented in large semi-field systems to (i) test the efficacy of Citriodiol® or transfluthrin-treated fabric strips positioned in house eave gaps as push components for preventing bites; (ii) understand the efficacy of MB5-baited Suna-traps in attracting vectors in the presence of a human being; (iii) assess 2-butanone as a CO2 replacement for trapping; (iv) determine the protection provided by a full push-pull set up. The air concentrations of the chemical constituents of the push-pull set-up were quantified. RESULTS: Microencapsulated Citriodiol® eave strips did not provide outdoor protection against host-seeking An. arabiensis. Transfluthrin-treated strips reduced the odds of a mosquito landing on the human volunteer (OR 0.17; 95% CI 0.12-0.23). This impact was lower (OR 0.59; 95% CI 0.52-0.66) during the push-pull experiment, which was associated with low nighttime temperatures likely affecting the transfluthrin vaporisation. The MB5-baited Suna trap supplemented with CO2 attracted only a third of the released mosquitoes in the absence of a human being; however, with a human volunteer in the same system, the trap caught < 1% of all released mosquitoes. The volunteer consistently attracted over two-thirds of all mosquitoes released. This was the case in the absence ('pull' only) and in the presence of a spatial repellent ('push-pull'), indicating that in its current configuration the tested 'pull' does not provide a valuable addition to a spatial repellent. The chemical 2-butanone was ineffective in replacing CO2. Transfluthrin was detectable in the air space but with a strong linear reduction in concentrations over 5 m from release. The MB5 constituent chemicals were only irregularly detected, potentially suggesting insufficient release and concentration in the air for attraction. CONCLUSION: This step-by-step evaluation of the selected 'push' and 'pull' components led to a better understanding of their ability to affect host-seeking behaviours of the malaria vector An. arabiensis in the peri-domestic space and helps to gauge the impact such tools would have when used in the field for monitoring or control.

Larvicidal Activity of Cinnamic Acid Derivatives: Investigating Alternative Products for Aedes aegypti L. Control.

The mosquito Aedes aegypti transmits the virus that causes dengue, yellow fever, Zika and Chikungunya viruses, and in several regions of the planet represents a vector of great clinical importance. In terms of mortality and morbidity, infections caused by Ae. aegypti are among the most serious arthropod transmitted viral diseases. The present study investigated the larvicidal potential of seventeen cinnamic acid derivatives against fourth stage Ae. aegypti larvae. The larvicide assays were performed using larval mortality rates to determine lethal concentration (LC50). Compounds containing the medium alkyl chains butyl cinnamate (7) and pentyl cinnamate (8) presented excellent larvicidal activity with LC50 values of around 0.21-0.17 mM, respectively. While among the derivatives with aryl substituents, the best LC50 result was 0.55 mM for benzyl cinnamate (13). The tested derivatives were natural compounds and in pharmacology and antiparasitic studies, many have been evaluated using biological models for environmental and toxicological safety. Molecular modeling analyses suggest that the larvicidal activity of these compounds might be due to a multi-target mechanism of action involving inhibition of a carbonic anhydrase (CA), a histone deacetylase (HDAC2), and two sodium-dependent cation-chloride co-transporters (CCC2 e CCC3).

Accelerating the Morphogenetic Cycle of the Viral Vector Aedes aegypti Larvae for Faster Larvicidal Bioassays.

Any bioassay to test new chemically synthesized larvicides or phytolarvicides against Culicidae and more harmful mosquito species, such as Aedes aegypti and Aedes albopictus, which specifically transmit dengue, yellow fever, chikungunya viral fevers as well as Zika virus, or Anopheles gambiae, a vector for malaria and philariasis, requires thousands of well-developed larvae, preferably at the fourth instar stage. The natural morphogenetic cycle of Aedes spp., in the field or in the laboratory, may extend to 19 days at room temperature (e.g., 25°C) from the first permanent contact between viable eggs and water and the last stage of larval growth or metamorphosis into flying adults. Thus, accelerated sequential molting is desirable for swifter bioassays of larvicides. We achieved this goal in Aedes aegypti with very limited strategic and low-cost additions to food, such as coconut water, milk or its casein, yeast extract, and to a lesser extent, glycerol. The naturally rich coconut water was excellent for quickly attaining the population of instar IV larvae, the most advanced one before pupation, saving about a week, for subsequent larvicidal bioassays. Diluted milk, as another food source, allowed an even faster final ecdysis and adults are useful for mosquito taxonomical purpose.

Impregnation of pectin-cedarwood essential oil nanocapsules onto mini cotton bag improves larvicidal performances.

The use pesticide is one of the indispensable means to combat mosquito borne diseases. However, the repeated use of synthetic pesticides has induced resistance in the vector pest along with undesirable impact on the environment. The biodegradability, non-persistent and user's safety are the root cause to prefer plant-derived pesticides to synthetic ones. The botanical based pesticides tend to degrade rapidly under the influence of several environmental factors. For the feasible application as pesticides, the plant products are formulated either as liquid or as purely solid. Despite well-established formulation technology in pesticide delivery, their handling trouble is being ignored. There is difficulty in liquid formulation of pesticide products, as they are prone to splashing and spillage, resulting in contamination, wastage and direct exposure to skin; whereas a solid formulation tends to produce dust. In the present work, cedarwood (Cedrus deodara) essential oil embedded pectin nanocapsules were produced. The nanocapsules were characterized according to their morphology, size, encapsulation efficiency and thermal stability. Furthermore, the nanocapsules were impregnated onto mini cotton tea bags to be employed as RTU (ready to use) formulation for treating the breeding sites of mosquitoes. The larvicidal activity of the bags treated with pectin-cedar wood nanocapsules was assessed against malaria vector, Anopheles culicifacies and 98% mortality was recorded till 4 weeks, this suggests its potential and hassle free applications in controlling mosquito vector.

Plant Natural Products for the Control of Aedes aegypti: The Main Vector of Important Arboviruses.

The mosquito species Aedes aegypti is one of the main vectors of arboviruses, including dengue, Zika and chikungunya. Considering the deficiency or absence of vaccines to prevent these diseases, vector control remains an important strategy. The use of plant natural product-based insecticides constitutes an alternative to chemical insecticides as they are degraded more easily and are less harmful to the environment, not to mention their lower toxicity to non-target insects. This review details plant species and their secondary metabolites that have demonstrated insecticidal properties (ovicidal, larvicidal, pupicidal, adulticidal, repellent and ovipositional effects) against the mosquito, together with their mechanisms of action. In particular, essential oils and some of their chemical constituents such as terpenoids and phenylpropanoids offer distinct advantages. Thiophenes, amides and alkaloids also possess high larvicidal and adulticidal activities, adding to the wealth of plant natural products with potential in vector control applications.

Insights on the Larvicidal Mechanism of Action of Fractions and Compounds from Aerial Parts of Helicteres velutina K. Schum against Aedes aegypti L.

Viral diseases transmitted by the female Aedes aegypti L. are considered a major public health problem. The aerial parts of Helicteres velutina K. Schum (Sterculiaceae) have demonstrated potential insecticidal and larvicidal activity against this vector. The objective of this research was to investigate the mechanisms of action involved in the larvicidal activity of this species. The cytotoxicity activity of H. velutina fractions and compounds of crude ethanolic extract of the aerial parts of this species was assessed by using fluorescence microscopy and propidium iodide staining. In addition, the production of nitric oxide (NO) and hemocyte recruitment were checked after different periods of exposure. The fluorescence microscopy revealed an increasing in larvae cell necrosis for the dichloromethane fraction, 7,4'-di-O-methyl-8-O-sulphate flavone and hexane fraction (15.4, 11.0, and 7.0%, respectively). The tiliroside did not show necrotic cells, which showed the same result as that seen in the negative control. The NO concentration in hemolymph after 24 h exposure was significantly greater for the dichloromethane fraction and the 7,4'-di-O-methyl-8-O-sulphate flavone (123.8 and 56.2 µM, respectively) when compared to the hexane fraction and tiliroside (10.8 and 8.3 µM, respectively). The presence of plasmocytes only in the dichloromethane fraction and 7,4'-di-O-methyl-8-O-sulphate flavone treatments suggest that these would be the hemocytes responsible for the highest NO production, acting as a defense agent. Our results showed that the larvicidal activity developed by H. velutina compounds is related to its hemocyte necrotizing activity and alteration in NO production.

Toxicological screening of marine red algae Champia parvula (C. Agardh) against the dengue mosquito vector Aedes aegypti (Linn.) and its non-toxicity against three beneficial aquatic predators.

Larval toxicity of ethanolic extract of C. parvula (Ex-Cp) was prominent in the second and the third instars at the maximum lethal dosage of 100 ppm with 98 and 97 % mortality rate respectively. The LC50 and LC90 was displayed at 43 ppm and 88 ppm dosage respectively. Correspondingly, the sub-lethal dosage (65 ppm) of Ex-Cp significantly alters the carboxylesterase (α and ß), GST and CYP450 enzyme level in both III and IV instar larvae in dose-dependent manner. Similarly, the Ex-Cp displayed significant repellent activity (97 %) with a maximum level of protection time (210 min). Photomicrography assay of Ex-Cp (65 ppm) were toxic to dengue larvae as compared to control. The non-target toxicity of Ex-Cp against the beneficial mosquito predators displayed less toxicity at the maximum dosage of 600 ppm as compared to Temephos. Thus the present research delivers the target and non-target toxicity of red algae C. parvula against the dengue mosquito vector.

Ascaridole-rich essential oil from marsh rosemary (Ledum palustre) growing in Poland exerts insecticidal activity on mosquitoes, moths and flies without serious effects on non-target organisms and human cells.

Marsh rosemary (Ledum palustre, Ericaceae) has been widely used in the traditional medicine of various regions worldwide, and as insect repellent. Little is known on its essential oil insecticidal potential. This study explored the insecticidal effects of the essential oil obtained from L. palustre growing in Poland on selected insect pests and vectors. GC-MS analysis evidenced an uncommon chemotype characterized by ascaridole (35.3% as sum of cis-ascaridole and isoascaridole) and p-cymene (25.5%). The essential oil was effective against Culex quinquefasciatus, Spodoptera littoralis and Musca domestica, showing LC50/LD50 of 66.6 mg L-1, 117.2 µg larva-1 and 61.4 µg adult-1, respectively. It was not toxic to non-target Eisenia fetida earthworms and moderately toxic to Daphnia magna microcrustaceans, over the positive control α-cypermethrin. The essential oil cytotoxicity on human keratinocytes and fibroblasts showed high IC50 values (71.3 and 84.4 µg mL-1, respectively). Comet assay data highlighted no DNA damages. Based on our findings, this essential oil, characterized by the ascaridole/p-cymene chemotype, could be a candidate for the formulation of botanical insecticides; large-scale production of green insecticides by this rare species may be assured by ex situ cultivation and biotechnological techniques.

Yeast-encapsulated essential oils: a new perspective as an environmentally friendly larvicide.

BACKGROUND: Effective mosquito control approaches incorporate both adult and larval stages. For the latter, physical, biological, and chemical control have been used with varying results. Successful control of larvae has been demonstrated using larvicides including insect growth regulators, e.g. the organophosphate temephos, as well as various entomopathogenic microbial species. However, a variety of health and environmental issues are associated with some of these. Laboratory trials of essential oils (EO) have established the larvicidal activity of these substances, but there are currently no commercially available EO-based larvicides. Here we report on the development of a new approach to mosquito larval control using a novel, yeast-based delivery system for EO. METHODS: Food-grade orange oil (OO) was encapsulated into yeast cells following an established protocol. To prevent environmental contamination, a proprietary washing strategy was developed to remove excess EO that is adsorbed to the cell exterior during the encapsulation process. The OO-loaded yeast particles were then characterized for OO loading, and tested for efficacy against Aedes aegypti larvae. RESULTS: The composition of encapsulated OO extracted from the yeast microparticles was demonstrated not to differ from that of un-encapsulated EO when analyzed by high performance liquid chromatography. After lyophilization, the oil in the larvicide comprised 26-30 percentage weight (wt%), and is consistent with the 60-65% reduction in weight observed after the drying process. Quantitative bioassays carried with Liverpool and Rockefeller Ae. aegypti strains in three different laboratories presented LD50 of 5.1 (95% CI: 4.6-5.6) to 27.6 (95% CI: 26.4-28.8) mg/l, for L1 and L3/L4 mosquito larvae, respectively. LD90 ranged between 18.9 (95% CI: 16.4-21.7) mg/l (L1 larvae) to 76.7 (95% CI: 69.7-84.3) mg/l (L3/L4 larvae). CONCLUSIONS: The larvicide based on OO encapsulated in yeast was shown to be highly active (LD50 < 50 mg/l) against all larval stages of Ae. aegypti. These results demonstrate its potential for incorporation in an integrated approach to larval source management of Ae. aegypti. This novel approach can enable development of affordable control strategies that may have significant impact on global health.

Phytochemical analysis of Rhazya stricta extract and its use in fabrication of silver nanoparticles effective against mosquito vectors and microbial pathogens.

Worldwide, billions of people are at risk from viruses, parasites and bacteria transmitted by mosquitoes, ticks, fleas and other vectors. Over exploitation of chemical pesticides to overcome the mosquito borne diseases led to detrimental effects on environment and human health. The present research aims to explore bio-fabrication of metal silver nanomaterials using Rhazya stricta extract against deadly mosquito vectors and microbial pathogens. The phytochemical profile of the R. stricta extracts was studied by HPLC-MS and 1H NMR. Further, confirmation of the bio-fabricated silver nanoparticles (AgNPs) was carried out by UV-vis spectroscopy and characterization through FTIR, TEM, EDX, and XRD analyses. The R. stricta-fabricated AgNPs showed acute toxicity on key mosquito vectors from two different country (India and Kingdom of Saudi Arabia, KSA) strains, notably, with LC50 values of 10.57, 11.89 and 12.78 µg/ml on malarial, dengue and filarial key Indian strains of mosquito vectors, respectively, and 30.66 and 38.39 µg/ml on KSA strains of Aedes aegypti and Culex pipiens, respectively. In mosquito adulticidal activity, R. stricta extract alone exhibited LC50 values ranging from 304.34 to 382.45 µg/ml against Indian strains and from 738.733 to 886.886 against Saudi Arabian strains, while AgNPs LC50 boosted from 9.52 to 12.16 µg/ml and from 30.66 to 38.39 µg/ml, respectively. Moreover, it was noticed that at low concentration the tested AgNPs showed high growth retardation of important pathogenic bacteria such as Bacillus subtilis, Klebsiella pneumoniae and Salmonella typhi with inhibition zone diameters from 11.86 to 22.92 mm. In conclusion, the present study highlighted that R. stricta-fabricated AgNPs could be a lead material for the management of mosquito vector and microbial pathogens control.

Diterpenes and their derivatives as promising agents against dengue virus and dengue vectors: A literature-based review.

Dengue, a mosquito-borne viral disease, causes about 100 million cases of infection annually. It is a major public concern, and if left untreated or improperly diagnosed, may cause serious health problems or even death. Historically, dengue has not considered priorities for pharmaceutical companies made the available treatment options. Therefore, medicinal scientists are revealing new insights and enabling novel interventions and approaches to dengue prevention and control. Diterpenes, a class of terpenes have gained much attention due to their diverse biological effects. This review aimed at summarizing available evidences of diterpenes and their derivatives acting against dengue virus and their vectors. For this, an updated search was made in the databases: PubMed and ScienceDirect by using specific keywords. Among the 117 published reports, a total of 30 articles was included in this review. Findings suggest that a number of diterpenes and/or their derivatives act against dengue virus and their two potential vectors namely Aedes aegypti and Ae. albopictus. In conclusion, diterpenes and their derivatives may have the potential alternative therapeutic tools for the management of dengue virus and some associated diseases transmitted by Aedes mosquito.

An Insight into the Discovery of Potent Antifilarial Leads Against Lymphatic Filariasis.

BACKGROUND AND OBJECTIVES: Lymphatic filariasis is a neglected tropical disease caused by infection with filarial worms that are transmitted through mosquito bites. Globally, 120 million people are infected, with nearly 40 million people disfigured and disabled by complications such as severe swelling of the legs (elephantiasis) or scrotum (hydrocele). Current treatments (ivermectin, diethylcarbamazine) have limited effects on adult parasites and produce side effects; therefore, there is an urgent to search for new antifilarial agents. Numerous studies on the antifilarial activity of pure molecules have been reported accross the recent literature. The present study describes the current standings of potent antifilarial compounds against lymphatic filariasis. METHODS: A literature search was conducted for naturally occurring and synthetic antifilarial compounds by referencing textbooks and scientific databases (SciFinder, PubMed, Science Direct, Wiley, ACS, SciELO, Google Scholar, and Springer, among others) from their inception until September 2019. RESULTS: Numerous compounds have been reported to exhibit antifilarial acitivity in adult and microfilariae forms of the parasites responsible for lymphatic filariasis. In silico studies of active antifilarial compounds (ligands) showed molecular interactions over the protein targets (trehalose-6-phosphate phosphatase, thymidylate synthase, among others) of lymphatic filariasis, and supported the in vitro results. CONCLUSION: With reference to in vitro antifilarial studies, there is evidence that natural and synthetic products can serve as basic scaffolds for the development of antifilarial agents. The optimization of the most potent antifilarial compounds can be further performed, followed by their in vivo studies.