Insecticidal activity of essential oils from American native plants against Aedes aegypti (Diptera: Culicidae): an introduction to their possible mechanism of action

Toxicological assessment of citral and geraniol: Efflux pump inhibition in Staphylococcus aureus and invertebrate toxicity

This study aimed to evaluate the antibacterial activity against multi-drug-resistant strains carrying efflux pumps and assess their toxicity on Drosophila melanogaster and Aedes aegypti models. Microdilution tests in broth were performed to determine the Minimum Inhibitory Concentration (MIC). The efflux pump inhibition was evaluated by analyzing the reduction in antibiotic MIC and Ethidium Bromide (EtBr) MIC when combined with the products. Mortality assay and negative geotaxis were conducted on D. melanogaster specimens, and insecticidal activity assays were performed on A. aegypti larvae. Only geraniol reduced the antibiotic MIC when combined, reducing from 64 µg/mL to 16 µg/mL in the 1199B strain of S. aureus. When combined with EtBr, both geraniol and citral reduced EtBr MIC, with geraniol decreasing from 64 µg/mL to 16 µg/mL and citral decreasing from 64 µg/mL to 32 µg/mL. Regarding the S. aureus K2068 strain, geraniol reduced the antibiotic MIC from 16 µg/mL to 8 µg/mL, and citral reduced it from 16 µg/mL to 4 µg/mL. In combination with EtBr, all monoterpenes reduced MIC from 64 µg/mL to 32 µg/mL. Both products exhibited toxicity in D. melanogaster; however, citral showed higher toxicity with a precisely determined LC50 of 2.478 μL. As for the insecticidal action on A. aegypti, both products demonstrated toxicity with cumulative effects and dose-dependent mortality.

Insecticidal activity of two Pelargonium essential oils and head transcriptome analysis of stored-product pest Tribolium castaneum (Herbst) (Coleoptera: Tenebrionidae) in response to citronellyl formate fumigation

Tribolium castaneum (Herbst) is one of the most common stored-product pests, causing enormous economic losses and developing widespread resistance to chemical insecticides. Natural products derived from essential oils (EOs) are well-known for insecticidal activity against agricultural pests, especially in the management of stored-product pests. In this study, the chemical constituents and repellent, contact and fumigation toxicity activities of two Pelargonium EOs against T. castaneum were evaluated. Moreover, the fumigation mechanism of citronellyl formate was assessed by head transcriptome sequencing and RNA interference (RNAi). A total of 28 and 39 compounds were identified by gas chromatography-mass spectrometry, accounting for 98.58 and 97.33 % of P. roseum and P. asperum EOs, and the major components were citronellol, (1S)-(1)-β-pinene and citronellyl formate. (1S)-(1)-β-Pinene exhibited strong contact toxicity activity (LD50 = 19.72 μg/adult), while citronellyl formate exhibited strong repellent and fumigation toxicity activities, with the LC50 value of 11.93 mg/L air. Under the stress of citronellyl formate, 1222 differentially expressed genes were identified, including 554 up-regulated and 668 down-regulated genes, which was further verified by qRT-PCR. Among odorant-binding proteins (OBPs), only TcGOBP70 was up-regulated, suggesting that GOBP70 is more likely to be involved in the defense of T. castaneum by recognizing, binding and transporting citronellyl formate. Additionally, RNAi against TcGOBP70 dramatically increased the contact and fumigation toxicity activities of citronellyl formate, with mortality rates of 73 and 75 %, respectively. Therefore, our findings not only provided theoretical bases for the comprehensive utilization of the Pelargonium species but also established potential targets for controlling T. castaneum adults.

Larvicidal Efficacies of Nanoliposomes Containing Alpha-pinene, Citral, Camphor, and Thymol Against Aedes aegypti and Anopheles stephensi Mosquito Vectors

BACKGROUND

Diseases transmitted by Aedes aegypti or Anopheles stephensi, such as Zika virus, dengue fever, and malaria, pose substantial risks to public health, particularly in tropical areas. Plant-derived compounds have emerged as promising alternatives due to their inherent safety and potential efficiency against mosquitoes. This study aimed to improve the efficacy of certain natural compounds, including α-pinene, citral, camphor, and thymol, by developing nanoliposomal formulations.

METHODS

The ‎nanoliposomes containing α-pinene, citral, camphor, and thymol were prepared using the ethanol injection method and then characterized. Using WHO-recommended guidelines, their larvicidal efficacy was investigated against Aedes aegypti and Anopheles stephensi.

RESULTS

The ‎nanoliposomes particle sizes were 105 ± 7, 86 ± 5, 149 ± 5, and 135 ± 8 nm, and zeta potentials ‎were - 25.1 ± 0.5, -17.2 ± 1.2, -16.4 ± 1.6, and - 21.3 ± 1.7 mV, respectively. In addition, the ATR-FTIR (Attenuated Total Reflectance-Fourier Transform InfraRed) analysis verified the successful loading of the compound. Nanoliposomal compounds exhibited superior performance compared to their non-formulated counterparts in larvicidal bioassays. The nanoliposomes containing thymol showed the highest efficacy, with a Lethal Concentration 50 (LC50) of 20 µg/mL against Ae. aegypti. Nanoliposomes containing citral exhibited an LC50 of 20 µg/mL against An. stephensi.

CONCLUSIONS

The results suggest that nanoliposomes have the potential to serve as an effective vehicle to improve the efficiency of plant-based larvicides. This could play a significant role in developing sustainable mosquito control strategies.

Insights into Molecular Mechanisms of Anticancer Activity of Juniperus communis Essential Oil in HeLa and HCT 116 Cells

As cancer remains a significant global health challenge, there is an increasing need for novel therapeutic approaches. We investigated the antitumor potential of Juniperus communis berry essential oil on cervical cancer HeLa and colorectal HCT 116 cells. Cytotoxicity was evaluated through the MTT assay, revealing concentration-dependent reductions in cell viability. A clonogenic assay demonstrated long-term cytotoxic effects. Apoptosis markers were assessed via flow cytometric analysis and showed an induction of the intrinsic pathway in both cell lines, demonstrated by the elevated levels of cleaved caspase-3, Bax/Bcl-2 ratio, JC-10 monomer formation, and cytochrome C migration to the cytosol. The treatment inhibited cell-survival pathways in HCT 116 cells and arrested HeLa cells in the S phase. An extensive molecular docking screening provided insight into the binding affinity and interaction patterns of the essential oil components with NADH ubiquinone oxidoreductase and superoxide dismutase enzymes, further confirming the induction of the intrinsic pathway of apoptosis. The obtained in silico and in vitro results indicated the anticancer potential of J. communis berry essential oil as it interferes with cancer cell molecular mechanisms. Our findings highlight J. communis berry essential oil as a promising natural agent with anticancer potential.

Towards Sustainable Pest Management: Toxicity, Biochemical Effects, and Molecular Docking Analysis of Ocimum basilicum (Lamiaceae) Essential Oil on Agrotis ipsilon and Spodoptera littoralis (Lepidoptera: Noctuidae)

Over the last decade, essential oils (EOs) have become potential ingredients for insecticide formulations due to their widespread availability and perceived safety. Therefore, this study aimed to evaluate the toxicity and biochemical efficacy of basil (Ocimum basilicum) (Lamiaceae) against two destructive pests Noctuidae, Agrotis ipsilon (Hufnagel) and Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). In addition, a molecular docking study was performed to gain insight into the binding pattern between glutathione S-transferase (GST) and linalool, the main component of EO. GC-MS analysis of O. basilicum EO revealed that linalool is the most abundant compound (29.34%). However, the toxicity tests showed no significant difference between the values of LC50 of O. basilicum EO to A. ipsilon and S. littoralis. On the other hand, the sublethal experiments indicated that treating the second instar larvae with LC15 or LC50 values of O. basilicum EO significantly prolonged the larval duration in both insects, compared to the control. Regarding the biochemical effect of O. basilicum EO, the treatments significantly impacted the activity of detoxification enzymes. A notable elevation in glutathione S-transferase (GST) activity was recorded in A. ipsilon larvae compared with a reduction in S. littoralis larvae. The molecular docking analysis revealed that linalool bonded with the amino acid serine (SER 9) of GST, indicating its binding affinity with the enzyme. The obtained results could offer valuable insights into the mode of action of O. basilicum and can encourage the adoption of sustainable pest control practices that incorporate essential oils.

Exploring the Larvicidal and Adulticidal Activity against Aedes aegypti of Essential Oil from Bocageopsis multiflora

This study investigates the chemical composition of the essential oil obtained from the leaves of Bocageopsis multiflora (Mart.) R.E.Fr (Annonaceae), examining its effectiveness in combating both the larvae and adult forms of Aedes aegypti mosquitoes. Additionally, for a deeper understanding of the insecticidal activity, toxicity properties and molecular docking calculations were conducted using the main compounds of this essential oil. GC/MS analysis revealed the presence of 26 constituents, representing 95.2% of the essential oil, with the major components identified as the sesquiterpenes α-selinene, β-selinene, and β-elemene. Larvicidal assays demonstrated potent activity of this essential oil with significant LC50 values of 40.8 and 39.4 μg/mL at 24 and 48 h, respectively. Adulticidal assessments highlighted strong efficacy with LC50 of 12.5 µg/mL. Molecular docking analysis identified optimal interaction activities of α-selinene and β-selinene with key Aedes proteins. The in silico studies comparing synthetic insecticides with the major sesquiterpenes of the essential oil revealed that β-selinene exhibited a significantly higher binding affinity compared to the other two sesquiterpenes. Also, ADMET studies of the three main sesquiterpenes indicated acceptable drug-like properties. In these findings, safety evaluations showed low toxicity and skin sensitization for the main sesquiterpenes, contrasting with commercial synthetic insecticides. Therefore, in silico analyses suggest promising interactions with Aedes proteins, indicating its potential as an effective alternative to conventional insecticides These results show the larvicidal and adulticidal potential of the essential oil from Bocageopsis multiflora against Aedes aegypti, supported by its predominant constituents, α-selinene, β-selinene and β-elemene.

Biological effects of Lippia alba essential oil against Anopheles gambiae and Aedes aegypti

The management of mosquito resistance to chemical insecticides and the biting behaviour of some species are motivating the search for complementary and/or alternative control methods. The use of plants is increasingly considered as a sustainable biological solution for vector control. The aim of this study was to evaluate the biological effects of the essential oil (EO) of Lippia alba harvested in Abidjan (Côte d'Ivoire) against Anopheles gambiae and Aedes aegypti mosquitoes. Phytochemical compounds were identified by GC-MS. Knockdown and mortality were determined according to the WHO test tube protocol. Contact irritancy was assessed by observing the movement of mosquitoes from a treated WHO tube to a second untreated tube. Non-contact repellency was assessed using a standardised high-throughput screening system (HITSS). Blood meal inhibition was assessed using a membrane feeding assay treated with EO. The EO was identified as the citral chemotype. The EO gave 100% KD60 in both species at a concentration of 1%. Mortalities of 100% were recorded with An. gambiae and Ae. aegypti at concentrations of 1% and 5% respectively. The highest proportions of females escaping during the contact irritancy test were 100% for An. gambiae at 1% concentration and 94% for Ae. aegypti at 2.5% concentration. The 1% concentration produced the highest proportions of repelled mosquitoes in the non-contact repellency tests: 76.8% (An. gambiae) and 68.5% (Ae. aegypti). The blood meal inhibition rate at a dose of 10% was 98.4% in Ae. aegypti but only 15.5% in An. gambiae. The citral chemotype of L. alba EO has promising biological effects in both species that make it a potentially good candidate for its use in mosquito control. The results obtained in this study encourage the further evaluation of L. alba EOs from other localities and of different chemotypes, under laboratory and field conditions.

Design and elucidation of an insecticide from natural compounds targeting mitochondrial proteins of Aedes aegypti

Developing new pesticides poses a significant challenge in designing next-generation natural insecticides that selectively target specific pharmacological sites while ensuring environmental friendliness. In this study, we aimed to address this challenge by formulating novel natural pesticides derived from secondary plant metabolites, which exhibited potent insecticide activity. Additionally, we tested their effect on mitochondrial enzyme activity and the proteomic profile of Ae. aegypti, a mosquito species responsible for transmitting diseases. Initially, 110 key compounds from essential oils were selected that have been reported with insecticidal properties; then, to ensure safety for mammals were performed in silico analyses for toxicity properties, identifying non-toxic candidates for further investigation. Subsequently, in vivo tests were conducted using these non-toxic compounds, focusing on the mosquito's larval stage. Based on the lethal concentration (LC), the most promising compounds as insecticidal were identified as S-limonene (LC50 = 6.4 ppm, LC95 = 17.2 ppm), R-limonene (LC50 = 9.86 ppm, LC95 = 27.7 ppm), citronellal (LC50 = 40.5 ppm, LC95 = 68.6 ppm), R-carvone (LC50 = 61.4 ppm, LC95 = 121 ppm), and S-carvone (LC50 = 62.5 ppm, LC95 = 114 ppm). Furthermore, we formulated a mixture of R-limonene, S-carvone, and citronellal with equal proportions of each compound based on their LC50. This mixture specifically targeted mitochondrial proteins and demonstrated a higher effect that showed by each compound separately, enhancing the insecticidal activity of each compound. Besides, the proteomic profile revealed the alteration in proteins involved in proliferation processes and detoxification mechanisms in Ae. aegypti. In summary, our study presents a formulation strategy for developing next-generation natural insecticides using secondary plant metabolites with the potential for reducing the adverse effects on humans and the development of chemical resistance in insects. Our findings also highlight the proteomic alteration induced by the formulated insecticide, showing insight into the mechanisms of action and potential targets for further exploration in vector control strategies.

Present status of insecticide impacts and eco-friendly approaches for remediation-a review

Insecticides are indispensable for modern agriculture to ensuring crop protection and optimal yields. However, their excessive use raises concerns regarding their adverse effects on agriculture and the environment. This study examines the impacts of insecticides on agriculture and proposes remediation strategies. Excessive insecticide application can lead to the development of resistance in target insects, necessitating higher concentrations or stronger chemicals, resulting in increased production costs and disruption of natural pest control mechanisms. In addition, non-target organisms, such as beneficial insects and aquatic life, suffer from the unintended consequences of insecticide use, leading to ecosystem imbalances and potential food chain contamination. To address these issues, integrated pest management (IPM) techniques that combine judicious insecticide use with biological control and cultural practices can reduce reliance on chemicals. Developing and implementing selective insecticides with reduced environmental persistence is crucial. Promoting farmer awareness of responsible insecticide use, offering training and resources, and adopting precision farming technologies can minimize overall insecticide usage.

Bioactivity of the Genus Turnera: A Review of the Last 10 Years

Turnera is a genus of plants whose biological activity has been widely studied. The importance of this genus, particularly Turnera diffusa, as a source of treatment for various conditions is evidenced by the large number of new studies that have evaluated its biological activity. Accordingly, the objective of this review was to compile the information published in the last ten years concerning the biological activities reported for Turnera spp. The present work includes 92 publications that evaluate 29 bioactivities and toxicological and genotoxic information on five species of this genus. Among the pharmacological effects reported, the antioxidant, hepatoprotective, neuroprotective, hypoglycemic, and aphrodisiac activities seem more promising. Phytochemicals and standardized plant extracts could offer alternative therapeutic remedies for various diseases. Although several flavonoids, cyanogenic glycosides, monoterpenoids, triterpenoids, and fatty acids have been isolated for Turnera plants, future research should focus on the identification of the main active principles responsible for these pharmacological activities, as well as to perform clinical trials to support the laboratory results.

Bioinsecticidal activity of cajeput oil to pyrethroid-susceptible and -resistant mosquitoes

Mosquito-borne diseases are a significant threat to human health. The frequent and repetitive application of insecticides can result in the selection of resistant mosquito populations leading to product failures for reducing community disease transmission. It is important that new interventions are discovered and developed for reducing mosquito populations and, in turn, protecting human health. Plant essential oils are promising chemical interventions for reducing mosquito populations. The myrtle family, Myrtaceae, has numerous species to be studied as potential bioinsecticides. Here, we combined toxicological, biochemical, and neurophysiological approaches to provide evidence for cajeput oil and terpene constituents to elicit bioinsecticidal activity to pyrethroid-susceptible and -resistant Aedes aegypti. We show cajeput oil terpenes to enhance cAMP production, increase ACh levels, inhibit in vivo and in vitro AChE activity, and disrupt spike discharge frequencies of the mosquito CNS. This study presents the first report on the bioinsecticidal activity of cajeput oil terpenes to pyrethroid-susceptible and -resistant mosquitoes and provides comparative data for the octopaminergic system as a putative molecular target for the bioinsecticides with implications for resistance management.

Antifungal and Antibiofilm Activity of Colombian Essential Oils against Different Candida Strains

Most Candida species are opportunistic pathogens with the ability to form biofilms, which increases their resistance to antifungal drug therapies and the host immune response. Essential oils (EOs) are an alternative for developing new antimicrobial drugs, due to their broad effect on cellular viability, cell communication, and metabolism. In this work, we evaluated the antifungal and antibiofilm potential of fifty EOs on C. albicans ATCC 10231, C. parapsilosis ATCC 22019, and Candida auris CDC B11903. The EOs’ antifungal activity was measured by means of a broth microdilution technique to determine the minimum inhibitory and fungicidal concentrations (MICs/MFCs) against the different Candida spp. strains. The effects on biofilm formation were determined by a crystal violet assay using 96-well round-bottom microplates incubated for 48 h at 35 °C. The EOs from Lippia alba (Verbenaceae family) carvone-limonene chemotype and L. origanoides exhibited the highest antifungal activity against C. auris. The L. origanoides EOs also presented antifungal and antibiofilm activity against all three Candida spp., thus representing a promising alternative for developing new antifungal products focused on yeast infections, especially those related to biofilm formation, virulence factors, and antimicrobial resistance.