High efficacy of (Z)-γ-bisabolene from the essential oil of Galinsoga parviflora (Asteraceae) as larvicide and oviposition deterrent against six mosquito vectors

Larvicidal, Ovicidal, and Repellent Activities of Leucas stachydiformis (Hochst. ex Benth.) Briq Essential Oil against Anopheles arabiensis

Larvicidal, ovicidal, and repellent activities of the essential oil extracted by hydrodistillation from the leaves of the endemic Ethiopian plant Leucas stachydiformis (Hochst. ex Benth.) Briq were investigated against Anopheles arabiensis, the dominant malaria vector species in Ethiopia with the objective of searching for a plant-based malaria vector control strategy from medicinal plants. The larvicidal effect was tested against the fourth instar An. arabiensis wild larvae whilst freshly laid ova of An. arabiensis were used to determine the ovicidal activity of the essential oil at concentrations ranging from 6.25 to 400 ppm. Concentrations of 41.6-366.7 µg/cm2 were used to evaluate the repellent activity of the essential oil on 3-5 days old adult female An. arabiensis. The oil composition of L. stachydiformis was also analyzed using GC-MS. The study revealed that the oil possesses the highest larvicidal activity at 400 ppm and 200 ppm after 24 h and 48 h of treatment. LC50 values for the fourth larval instar after 24 h and 48 h of treatment were 43.4 ppm and 34.2 ppm, respectively. After 72 h of exposure, the oil displayed 100% ovicidal activity at 400 ppm with an IH50 value of 32.2 ppm. In the repellency test, at concentrations of 366.7, 133.3, and 41.6 µg/cm2, the oil gave a total percentage protection of 67.9 ± 4.2%, 37.2 ± 2.8%, and 32 ± 2.2%, respectively, for 4 h. The highest concentration (366.7 µg/cm2) gave 100% protection up to 90 min. GC-MS analysis of the oil revealed the presence of 24 compounds representing 90.34% of the total oil with caryophyllene oxide, germacrene D, and trans-caryophyllene constituting more than 50% of its components. Results of the present study suggest that the essential oil of L. stachydiformis has the potential to be used for the control of An. arabiensis mosquitoes.

The Potentials of Ageratum conyzoides and Other Plants from Asteraceae as an Antiplasmodial and Insecticidal for Malaria Vector: An Article Review

Background

Malaria is a life-threatening disease prevalent in tropical and subtropical regions. Artemisinin combination therapy (ACT) used as an antimalarial treatment has reduced efficacy due to resistance, not only to the parasite but also to the vector. Therefore, it is important to find alternatives to overcome malaria cases through medicinal plants such as Ageratum conyzoides and other related plants within Asteraceae family.

Purpose

This review summarizes the antimalarial and insecticidal activities of A. conyzoides and other plants belonging to Asteraceae family.

Data Source

Google Scholar, PubMed, Science Direct, and Springer link.

Study Selection

Online databases were used to retrieve journals using specific keywords combined with Boolean operators. The inclusion criteria were articles with experimental studies either in vivo or in vitro, in English or Indonesian, published after 1st January 2000, and full text available for inclusion in this review.

Data Extraction

The antimalarial activity, insecticidal activity, and structure of the isolated compounds were retrieved from the selected studies.

Data Synthesis

Antimalarial in vitro study showed that the dichloromethane extract was the most widely studied with an IC50 value <10 μg/mL. Among 84 isolated active compounds, 2-hydroxymethyl-non-3-ynoic acid 2-[2,2']-bithiophenyl-5- ethyl ester, a bithienyl compound from the Tagetes erecta plant show the smallest IC50 with value 0.01 and 0.02 µg/mL in Plasmodium falciparum MRC-pf-2 and MRC-pf-56, respectively. In vivo studies showed that the aqueous extract of A. conyzoides showed the best activity, with a 98.8% inhibition percentage using a 100 mg/kg dose of Plasmodium berghei (NK65 Strain). (Z)- γ-Bisabolene from Galinsoga parviflora showed very good insecticidal activity against Anopheles stephensi and Anopheles subpictus with LC50 values of 2.04 μg/mL and 4.05 μg/mL.

Conclusion

A. conyzoides and other plants of Asteraceae family are promising reservoirs of natural compounds that exert antimalarial or insecticidal activity.

Chemical Composition, Larvicidal and Molluscicidal Activity of Essential Oils of Six Guava Cultivars Grown in Vietnam

Diseases transmitted by mosquitoes and snails cause a large burden of disease in less developed countries, especially those with low-income levels. An approach to control vectors and intermediate hosts based on readily available essential oils, which are friendly to the environment and human health, may be an effective solution for disease control. Guava is a fruit tree grown on a large scale in many countries in the tropics, an area heavily affected by tropical diseases transmitted by mosquitoes and snails. Previous studies have reported that the extracted essential oils of guava cultivars have high yields, possess different chemotypes, and exhibit toxicity to different insect species. Therefore, this study was carried out with the aim of studying the chemical composition and pesticide activities of six cultivars of guava grown on a large scale in Vietnam. The essential oils were extracted by hydrodistillation using a Clevenger-type apparatus for 6 h. The components of the essential oils were determined using gas-chromatography-mass-spectrometry (GC-MS) analysis. Test methods for pesticide activities were performed in accordance with WHO guidelines and modifications. Essential oil samples from Vietnam fell into two composition-based clusters, one of (E)-β-caryophyllene and the other of limonene/(E)-β-caryophyllene. The essential oils PG03 and PG05 show promise as environmentally friendly pesticides when used to control Aedes mosquito larvae with values of 24 h LC50-aegypti of 0.96 and 0.40 µg/mL while 24 h LC50-albopictus of 0.50 and 0.42 µg/mL. These two essential oils showed selective toxicity against Aedes mosquito larvae and were safe against the non-target organism Anisops bouvieri. Other essential oils may be considered as molluscicides against Physa acuta (48 h LC50 of 4.10 to 5.00 µg/mL) and Indoplanorbis exustus (48 h LC50 of 3.85 to 7.71 µg/mL) and with less toxicity to A. bouvieri.

Galinsoga parviflora (Cav.): A comprehensive review on ethnomedicinal, phytochemical and pharmacological studies

Galinsoga parviflora (Cav.) is a member of the Asteraceae family traditionally used for treatment of various ailments such as malaria, flu, cold, colorectal cancer, liver problems and inflammation. The medicinal properties of G. parviflora are due to the presence of various secondary metabolites including flavonoids, saponins, terpenoids and tannins. The literature survey revealed that G. parviflora possesses several pharmacological properties such as antibacterial, antifungal, antioxidant and antidiabetic. This review systematically discusses the potential of G. parviflora for managing medical conditions. The information is collected from various online databases such as Google Scholar, ScienceDirect, Springer, Web of Science, Plant of the World Online and PubMed. Among other information provided in this review, ethnomedicinal uses, phytochemistry and pharmacological activities are discussed extensively. Additonally, the potential benefits, challenges and future opportunities are presented.

Chemical Composition and Antifungal Activity of Myrcia multiflora and Eugenia florida Essential Oils

The essential oils of three specimens of Myrcia multiflora (A, B and C) and Eugenia florida were extracted by hydrodistillation, and the chemical compositions from the essential oils were identified by gas chromatography and flame ionization detection (CG/MS and CG-FID). The fungicide potential of the EOs against five fungicide yeasts was assessed: Candida albicans INCQS-40175, C. tropicalis ATCC 6258, C. famata ATCC 62894, C. krusei ATCC 13803 and C. auris IEC-01. The essential oil of the specimen Myrcia multiflora (A) was characterized by the major compounds: α-bulnesene (26.79%), pogostol (21.27%) and δ-amorphene (6.76%). The essential oil of the specimen M. multiflora (B) was rich in (E)-nerolidol (44.4%), (E)-γ-bisabolene (10.64%) and (E,E)-α-farnesene (8.19%), while (E)-nerolidol (92.21%) was the majority of the specimen M. multiflora (C). The sesquiterpenes seline-3,11-dien-6-α-ol (12.93%), eremoligenol (11%) and γ-elemene (10.70%) characterized the chemical profile of the EOs of E. florida. The fungal species were sensitive to the essential oil of M. multiflora (B) (9-11 mm), and the lowest inhibitory concentration (0.07%) was observed in the essential oil of M. multiflora (A) against the yeasts of C. famata. Fungicidal action was observed in the essential oils of M. multiflora (A) against C. famata, with an MIC of 0.78 µL/mL and 3.12 µL/mL; C. albicans, with an MFC of 50 µL/mL and M. multiflora (C) against C. albicans; and C. krusei, with a MFC of 50 µL/mL.

Naturally Occurring Compounds With Larvicidal Activity Against Malaria Mosquitoes

Female Anopheles mosquitoes transmit Plasmodium parasites that cause human malaria. Currently, vector control is the most widely deployed approach to reduce mosquito population and hence disease transmission. This relies on use of insecticide-based interventions including Long-lasting Insecticide-treated Nets (LLINs) and Indoor Residual Spraying (IRS) where scale-up has contributed to a dramatic decline in malaria deaths and morbidity over the past decade. Challenges to their effective use include the emergence and spread of insecticide resistance by malaria vector populations coupled with the inability to curb outdoor transmission. Under these situations, use of larvicides through larval source management (LSM) can complement these existing measures. The need to minimize environmental impact and effect on non-target organisms has spurred interest in the development of eco-friendly larvicides of natural origin. Here, we review literature published in the last five years to highlight compounds of natural origin found to exhibit larvicidal activity against malaria mosquitoes. Specifically, the larvicidal activity of different classes of compounds is discussed including their effect on non-target organisms. Additionally, we provide suggestions for future research into mosquito larvicides including the use of chemical synthesis to improve the bioactivity of known natural compounds.

In Silico and In Vitro Evaluation of the Antimicrobial and Antioxidant Potential of Mentha × smithiana R. GRAHAM Essential Oil from Western Romania

This study was conducted to identify the volatile compounds of Mentha × smithiana essential oil (MSEO) and evaluate its antioxidant and antibacterial potential. The essential oil (EO) content was assessed by gas chromatography-mass spectrometry (GC-MS). Carvone (55.71%), limonene (18.83%), trans-carveol (3.54%), cis-carveol (2.72%), beta-bourbonene (1.94%), and caryophyllene oxide (1.59%) were the main identified compounds. The MSEO displayed broad-spectrum antibacterial effects and was also found to be the most effective antifungal agent against Candida albicans and Candida parapsilosis. The antioxidant activity of MSEO was tested against cold-pressed sunflower oil by peroxide, thiobarbituric acid, 1,1-diphenyl-2-picrylhydrazyl radical (DPPH), and β-carotene/linoleic acid bleaching methods. The EO showed strong antioxidant effects as reflected by IC50 values of 0.83 ± 0.01 mg/mL and relative antioxidative activity of 87.32 ± 0.03% in DPPH and β-carotene/linoleic acid bleaching assays, respectively. Moreover, in the first 8 days of the incubation period, the inhibition of primary and secondary oxidation compounds induced by the MSEO (0.3 mg/mL) was significantly stronger (p < 0.05) than that of butylated hydroxyanisole. In silico molecular docking studies were conducted to highlight the underlying antimicrobial mechanism as well as the in vitro antioxidant potential. Recorded data showed that the antimicrobial activity of MSEO compounds could be exerted through the D-Alanine-d-alanine ligase (DDl) inhibition and may be attributed to a cumulative effect. The most active compounds are minor components of the MSEO. Docking results also revealed that several mint EO components could exert their in vitro antioxidant activity by employing xanthine oxidase inhibition. Consequently, MSEO could be a new natural source of antioxidants and antiseptics, with potential applications in the food and pharmaceutical industries as an alternative to the utilization of synthetic additives.

Essential oils and their chemical constituents against Aedes aegypti L. (Diptera: Culicidae) larvae

This review focused on the toxicity of essential oils and their constituents against Aedes aegypti L. (Diptera, Culicidae) larvae, a key vector of important arboviral diseases, such as dengue, chikungunya, zika, and yellow fever. This review is based on original articles obtained by searching major databases in the last six years. Our literature review shows that 337 essential oils from 225 plant species have been tested for larvicidal bioactivity. More than 60% of these essential oils were considered active (LC₅₀<100 µg/mL). Most species belong to the families Lamiaceae (19.3%), Lauraceae (9.9%), and Myrtaceae (9.4%). The plants studied for their larvicidal activity against A. aegypti were mainly collected in India and Brazil (30 and 20%, respectively) and the parts of the plants most used were the leaves. Less than 10% of essential oils were evaluated for toxicity against non-target organisms and with the aim to demonstrate safe use. The most used plant parts are leaves and the main compounds of essential oils were described. The most active essential oils are rich in sesquiterpene hydrocarbons, oxygenated sesquiterpenes, and monoterpene hydrocarbons. Here, factors affecting bioactivity (chemical composition, plant parts, and harvesting site) of essential oils and their constituents, as well as safety to non-target organisms are discussed. Essential oils have considerable potential against A. aegypti. This review shows that essential oils might be used to control arboviruses, and further studies on safety and formulations for application in the field should be performed.

Chemical, biological and in silico assessment of Ocimum viride essential oil

AIMS

Ocimum viride Willd. (family: Lamiaceae) is a member of the genus Ocimum, an aromatic annual and perennial herb with numerous culinary, horticultural and ethno-medicinal benefits. This study aims to explore the chemical properties of leaf essential oil (EO) from Ocimum viride and to evaluate its antimicrobial and anticancer potential.

MAIN METHODS

Characterization of essential oil was done by GCMS, antimicrobial by agar well diffusion methods, in vitro cytotoxicity evaluation by MTT assay, cell death analysis was done by DNA fragmentation, cell cycle analysis, nuclear morphology analysis and molecular docking studies were also conducted.

KEY FINDINGS

Essential oil from aerial parts (leaf) of Ocimum viride revealed high content of oxygenated monoterpenes, notably thymol (~50%) and γ-terpinene (~18%). Further, antibacterial analysis showed that among all the evaluated bacterial species EO showed highest sensitivity against the Bacillus subtilis and was also found most effective against HT-29 colon cancer cell line with IC50 value of ~0.034 ± 0.001μL/mL. Mechanistic studies revealed that EO inhibits the growth of HT-29 colon cancer cells probably through induction of irreparable DNA damage leading to subsequent cell death in apoptotic manner. Molecular docking analysis also supports the in vitro studies conducted by indicating the interaction of thymol with Sec A protein of Bacillus subtilis cell wall as well as with Beclin protein responsible for apoptotic corpse clearance.

SIGNIFICANCE

Taken together, our results indicate that EO possesses potent antimicrobial and anticancer properties, and may find applications as effective antibacterial and in cancer therapeutics.

Eco-friendly pesticide based on peppermint oil nanoemulsion: preparation, physicochemical properties, and its aphicidal activity against cotton aphid

Using organic insecticides including plant oils, it is possible to design a new perspective for the control of insect pests. In this research, nanoemulsion formulations of Mentha piperita, wild-type essential oil (EO) were prepared utilizing high-energy ultrasonication process. Physicochemical properties of nanoemulsions were precisely studied by measurement various parameters including pH, viscosity, conductivity, and zeta potential. Experimental design by the aid of response surface methodology (RSM) was used to highlight the physicochemical roles of EO percentage (1% to 5% (v/v)) and surfactant concentration (3% to 15% (v/v)) for achieving minimum droplet diameter with high physical stability. The nanoemulsion formulations were then characterized using dynamic light scattering, transmission electron microscopy, and optical clarity. Afterward, an appropriate model between the variable factors (EO percentage and surfactant concentration) and the response (hydrodynamic particle size) was statistically developed. Under the optimum conditions, nanoemulsion with hydrodynamic particle size less than 10 nm with high physical stability is obtainable. Bioassay experiments were carried out to elucidate the effects of nanoemulsion on the cotton aphid. Synthesized nanoemulsion formulations showed relatively high contact toxicity (average value of LC₅₀ was about 3879.5 ± 16.2 μl a.i./L) against the pest. On the basis of the obtained results, prepared nanoemulsion using M. piperita is potentially applicable as organic insecticides against cotton aphid. Graphical abstract.

How Central Is the Domestic Pig in the Epidemiological Cycle of Japanese Encephalitis Virus? A Review of Scientific Evidence and Implications for Disease Control

Despite the existence of human vaccines, Japanese encephalitis (JE) remains the leading cause of human encephalitis in Asia. Pigs are described as the main amplifying host, but their role in JE epidemiology needs to be reassessed in order to identify and implement efficient control strategies, for both human and animal health. We aimed to provide a systematic review of publications linked to JE in swine, in terms of both individual and population characteristics of JE virus (JEV) infection and circulation, as well as observed epidemiological patterns. We used the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) statement to select and analyze relevant articles from the Scopus database, 127 of which were included in the review. Pigs are central, but the implication of secondary hosts cannot be ruled out and should be further investigated. Although human vaccination cannot eradicate the virus, it is clearly the most important means of preventing human disease. However, a better understanding of the actual involvement of domestic pigs as well as other potential JEV hosts in different JEV epidemiological cycles and patterns could help to identify additional/complementary control measures, either by targeting pigs or not, and in some specific epidemiological contexts, contribute to reduce virus circulation and protect humans from JEV infection.

Development and evaluation of emulsifiable concentrate formulation containing Sophora alopecuroides L. extract for the novel management of Asian citrus psyllid

Utilization of non-host plants semiochemicals to mediate insect behavior offers a promising opportunity for novel management of insect pests in field crops and fruits. Therefore, there is still a substantial opportunity for the development of natural prophylactic as an eco-friendly approach in the novel pest management programs. Sophora alopecuroides extract has been used as a natural pesticide in the control of agricultural and household pests, but the low persistence effect and rapid biodegradability limit its use on a wider scale in pest management programs. In this study, an emulsifiable concentrate formulation containing S. alopecuroides extract (SAE-EC) was developed with a simple procedure and evaluated for its ovicidal, antifeedant, and repellent effects against Diaphorina citri under laboratory and semi-field conditions. Our results indicated that SAE-EC at 15, 30, and 50 mg/mL concentrations provide complete protection against psyllids for a period of 96 h after application both under laboratory and semi-field conditions, while the aqueous methanolic extract of S. alopecuroides loses its persistence 48 h after application. Furthermore, the emulsifiable concentrate at 20 and 30 mg/mL concentrations, only 15.97% and 31.97% of eggs were able to hatch, and at similar concentrations, 72.86% and 85.5% of honeydew secretion were reduced as compared to the control. SAE-EC at 30 mg/mL concentration has not shown any phytotoxic symptoms on Murraya paniculata seedlings. Fourier transform infrared (FTIR) study revealed the presence of alkaloids in emulsifiable concentrate after 3 months of its preparation placed under ambient temperature. Furthermore, the particle size and polydispersity index (PDI) of the emulsifiable concentrate were also confirmed by dynamic light scattering (DLS). Our finding indicated that emulsifiable concentrate formulation prolongs the persistence of S. alopecuroides extract and enhances its efficacy both under laboratory and semi-field conditions. It has been concluded that the emulsifiable concentrate formulation containing S. alopecuroides extract might be developed as an eco-friendly novel prophylactic against citrus psyllid.

Plant-based larvicidal agents: An overview from 2000 to 2018

Current review aims to systematically segregate, analyze and arrange the key findings of the scientific reports published on larvicidal plants including larvicidal formulations. The investigation was carried out by analyzing the published literature in various scientific databases, subsequently, the key findings of the selective scientific reports having larvicidal potency (LC₅₀) of extract or isolated oil<100 μg/mL were tabulated to provide the concise and crucial information. Special emphasis was given on reports in which LC₅₀ of extract or isolated oil was reported to be < 10 μg/mL, genus or species documented in multiple independent studies, advancement in larvicidal formulations and activity of isolated phytoconstituents. Extensive analysis of published literature revealed that the larvicidal potency of herbal resources varied from sub-microgram/ml to practically insignificant. Overall, this unprecedented summarized and arranged information can be utilized for design, development and optimization of herbal based formulation having potential larvicidal activity.

Evaluation of (-)-borneol derivatives against the Zika vector, Aedes aegypti and a non-target species, Artemia sp

Zika, dengue, and chikungunya are vector-borne diseases of pronounced concern transmitted by the mosquito Aedes aegypti Linn. (Diptera: Culicidae). The most important method to avoid outbreaks is to control mosquito spreading by the employment of insecticides and larvicides. Failure to control mosquito dispersal is mostly accounted to Ae. aegypti resistance to currently available larvicides and insecticides, encouraging the development of novel pesticides. In addition, the excessive use of larvicides poses serious threats to human health and the environment. Evaluation of natural products as larvicides in an attempt to overcome this situation is often found in the literature because products originated from nature are considered less toxic to non-target species and more eco-friendly. (-)-Borneol is a bicyclic monoterpene present in essential oils with moderate larvicidal activity. On account of these facts, it was of our interest to synthesize (-)-borneol ester derivatives aiming to study its structure-activity relationships against Ae. aegypti larvae. With the goal to estimate toxicity to a non-target species, evaluation of the lethal concentration 50% (LC₅₀) on Artemia sp. (Artemiidae) and calculation of selectivity towards Ae. aegypti were carried out. The most potent derivative, (-)-Bornyl chloroacetate, exhibited the highest suitability index, demonstrating lower environmental toxicity than other borneol ester derivatives. A parabolic relationship between (-)-borneol esters larvicidal activity and partition coefficient (Log P) was achieved and a correlation equation obtained, validating the importance of lipophilicity to the larvicidal activity of these compounds.