Essential oil of Piper purusanum C.DC (Piperaceae) and its main sesquiterpenes: biodefensives against malaria and dengue vectors, without lethal effect on non-target aquatic fauna

Essential oil from Piper tuberculatum Jacq. (Piperaceae) and its majority compound β-caryophyllene: mechanism of larvicidal action against Aedes aegypti (Diptera: Culicidae) and selective toxicity

Synthetic insecticides have been the primary approach in controlling Aedes aegypti; however, their indiscriminate use has led to the development of resistance and toxicity to non-target animals. In contrast, essential oils (EOs) are alternatives for vector control. This study investigated the mechanism of larvicidal action of the EO and β-caryophyllene from Piper tuberculatum against A. aegypti larvae, as well as evaluated the toxicity of both on non-target animals. The EO extracted from P. tuberculatum leaves was majority constituted of β-caryophyllene (54.8%). Both demonstrated larvicidal activity (LC50 of 48.61 and 57.20 ppm, p < 0.05), acetylcholinesterase inhibition (IC50 of 57.78 and 71.97 ppm), and an increase in the production of reactive oxygen and nitrogen species in larvae after exposure to the EO and β-caryophyllene. Furthermore, EO and β-caryophyllene demonstrate no toxicity to non-target animals Toxorhynchites haemorrhoidalis, Anisops bouvieri, and Diplonychus indicus (100% of survival rate), while the insecticide α-cypermethrin was highly toxic (100% of death). The results demonstrate that the EO from P. tuberculatum and β-caryophyllene are important larvicidal agents.

Essential oil and fenchone extracted from Tetradenia riparia (Hochstetter.) Codd (Lamiaceae) induce oxidative stress in Culex quinquefasciatus larvae (Diptera: Culicidae) without causing lethal effects on non-target animals

We investigated the larvicidal activity of the essential oil (EO) from Tetradenia riparia and its majority compound fenchone for controlling Culex quinquefasciatus larvae, focusing on reactive oxygen and nitrogen species (RONS), catalase (CAT), glutathione S-transferase (GST), acetylcholinesterase (AChE) activities, and total thiol content as oxidative stress indicators. Moreover, the lethal effect of EO and fenchone was evaluated against Anisops bouvieri, Diplonychus indicus, Danio rerio, and Paracheirodon axelrodi. The EO and fenchone (5 to 25 µg/mL) showed larvicidal activity (LC50 from 16.05 to 18.94 µg/mL), followed by an overproduction of RONS, and changes in the activity of CAT, GST, AChE, and total thiol content. The Kaplan-Meier followed by Log-rank (Mantel-Cox) analyses showed a 100% survival rate for A. bouvieri, D. indicus, D. rerio, and P. axelrodi when exposed to EO and fenchone (262.6 and 302.60 µg/mL), while α-cypermethrin (0.25 µg/mL) was extremely toxic to these non-target animals, causing 100% of death. These findings emphasize that the EO from T. riparia and fenchone serve as suitable larvicides for controlling C. quinquefasciatus larvae, without imposing lethal effects on the non-target animals investigated.

Oxidative stress induction by essential oil from Piper alatipetiolatum (Piperaceae) triggers lethality in the larvae of Culex quinquefasciatus (Diptera: Culicidae)

Culex quinquefasciatus is the main vector of lymphatic filariasis in Brazil, which present resistance to commercial insecticides. Nowadays, essential oils (EOs) exhibiting larvicidal activity, such as those derived from Piper alatipetiolatum, provide a promising alternative for vector control, including Culex species. This study aimed to investigate the larvicidal activity and the oxidative stress indicators of the EO from P. alatipetiolatum in Cx. quinquefasciatus larvae. The EO was extracted from P. alatipetiolatum leaves using the hydrodistillation method, resulting in a yield of 7.2 ± 0.1%, analysed by gas chromatography coupled with spectrometry and gas chromatography coupled with flame ionization detector (GC-MS and GC-FID), and evaluated against Cx. quinquefasciatus larvae. Reactive Oxygen and Nitrogen Species (RONS), Catalase (CAT), glutathione-S-transferase (GST), acetylcholinesterase (AChE), and Thiol levels were used as oxidative stress indicators. Analysis by CG-MS and CG-FID revealed that the main compound in the EO was the oxygenated sesquiterpene ishwarone, constituting 78.6% of the composition. Furthermore, the EO exhibited larvicidal activity, ranging from 26 to 100%, with an LC50 of 4.53 μg/mL and LC90 of 15.37 μg/mL. This activity was accompanied by a significant increase in RONS production, alterations in CAT, GST, AChE activity, and thiol levels compared to the control groups (p < 0.05). To the best of our knowledge, this is the first report describing the larvicidal activity and oxidative stress induced by the EO from P. alatipetiolatum against Cx. quinquefasciatus larvae. Therefore, we propose that this EO shows promise as larvicidal agent for the effective control of Cx. quinquefasciatus larvae.

Insecticidal activity of essential oil from leaves of Eugenia stipitata McVaugh against Aedes aegypti

Aedes aegypti, a mosquito, is responsible for the spread of many diseases, including dengue, zika, and chikungunya. However, due to this mosquito's developed resistance to conventional pesticides, effectively controlling it has proven to be challenging. This study aimed to evaluate the insecticidal potential of the essential oil from the leaves of Eugenia stipitata against Ae. aegypti, offering a natural and sustainable alternative for mosquito control. Tests were conducted using third-stage larvae to evaluate larvicidal activity and pupae collected up to 14 h after transformation to investigate pupicidal activity. Throughout the bioassays, the organisms were exposed to various essential oil concentrations. The findings demonstrated that the essential oil of E. stipitata exhibited larvicidal action, resulting in 100% larval mortality after 24 h and an LC50 value of 0.34 mg/mL. The effectiveness of essential oil as a pupicidal agent was also demonstrated by its LC50 value of 2.33 mg/mL and 100% larval mortality in 24 h. It can be concluded that the essential oil of E. stipitata holds promise as a natural pest control agent. Its use may reduce the reliance on conventional chemical pesticides, providing a more sustainable and effective strategy to combat diseases spread by mosquitoes.

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.

Assessing the Larvicidal Properties of Endemic Campeche, Mexico Plant Piper cordoncillo var. apazoteanum (Piperaceae) against Aedes aegypti (Diptera: Culicidae) Mosquitoes

The research aims to investigate the mortality effect of essential oil from Piper cordoncillo var. apazoteanum, an endemic plant from Campeche, Mexico, on early second-instar Aedes aegypti larvae; it also aims to identify the volatile compounds present in the fresh leaves of the plant. To test the effectiveness of the essential oil, we followed World Health Organization Standard Procedures. Larvae were observed for 17 consecutive days after treatment to determine the mortality and growth-inhibitory effect exerted by the essential oil. The results showed that the essential oil was effective in controlling mosquito populations. At a concentration of 800 ppm, the oil achieved an effectiveness rate of 70.00 ± 8.16% after 24 h, increasing to 100.00 ± 0.01% mortality after 72 h. With a concentration of 400 ppm, the effectiveness was 98.33 ± 0.17% by the end of the experiment. Furthermore, the obtained results demonstrated that the LC₅₀ value was 61.84 ± 6.79 ppm, while the LC₉₀ value was 167.20 ± 11.49 ppm. Essential oil concentrations inhibited the growth of immature insect stages, with concentrations between 800-100 ppm demonstrating very high inhibitory activity, and the lowest concentration of 50 ppm showing high inhibitory activity. The study also identified 24 chemical compounds representing 86.71% of the volatile compound composition of the fresh leaves of P. cordoncillo; the most abundant compounds were Safrole, Caryophyllene oxide, E-Nerolidol, and Calarene epoxide. The method used to extract the volatile compounds, solvent-free microwave extraction (SFME), is a promising alternative to traditional methods that avoids the use of potentially harmful solvents, making it more ecologically friendly and potentially safer for professionals handling the extracted compounds. Overall, the study demonstrates the potential of P. cordoncillo essential oil as an effective means of controlling mosquito populations, and provides valuable information on the chemical composition of the plant.Moreover, our study is the first to report on the biological activity and chemical composition of P. cordoncillo worldwide.

Chemistry and Bioactivity of Croton Essential Oils: Literature Survey and Croton hirtus from Vietnam

Using essential oils to control vectors, intermediate hosts, and disease-causing microorganisms is a promising approach. The genus Croton in the family Euphorbiaceae is a large genus, with many species containing large amounts of essential oils, however, essential oil studies are limited in terms of the number of Croton species investigated. In this work, the aerial parts of C. hirtus growing wild in Vietnam were collected and analyzed by gas chromatography/mass spectrometry (GC/MS). A total of 141 compounds were identified in C. hirtus essential oil, in which sesquiterpenoids dominated, comprising 95.4%, including the main components β-caryophyllene (32.8%), germacrene D (11.6%), β-elemene (9.1%), α-humulene (8.5%), and caryophyllene oxide (5.0%). The essential oil of C. hirtus showed very strong biological activities against the larvae of four mosquito species with 24 h LC₅₀ values in the range of 15.38-78.27 μg/mL, against Physella acuta adults with a 48 h LC₅₀ value of 10.09 μg/mL, and against ATCC microorganisms with MIC values in the range of 8-16 μg/mL. In order to provide a comparison with previous works, a literature survey on the chemical composition, mosquito larvicidal, molluscicidal, antiparasitic, and antimicrobial activities of essential oils of Croton species was conducted. Seventy-two references (seventy articles and one book) out of a total of two hundred and forty-four references related to the chemical composition and bioactivity of essential oils of Croton species were used for this paper. The essential oils of some Croton species were characterized by their phenylpropanoid compounds. The experimental results of this research and the survey of the literature showed that Croton essential oils have the potential to be used to control mosquito-borne and mollusk-borne diseases, as well as microbial infections. Research on unstudied Croton species is needed to search for species with high essential oil contents and excellent biological activities.

Essential Oils of Aromatic Plant Species from the Atlantic Rainforest Exhibit Extensive Chemical Diversity and Antimicrobial Activity

Microbial resistance, caused by the overuse or inadequate application of antibiotics, is a worldwide crisis, increasing the risk of treatment failure and healthcare costs. Plant essential oils (EOs) consist of hydrophobic metabolites with antimicrobial activity. The antimicrobial potential of the chemical diversity of plants from the Atlantic Rainforest remains scarcely characterized. In the current work, we determined the metabolite profile of the EOs from aromatic plants from nine locations and accessed their antimicrobial and biocidal activity by agar diffusion assays, minimum inhibitory concentration, time-kill and cell-component leakage assays. The pharmacokinetic properties of the EO compounds were investigated by in silico tools. More than a hundred metabolites were identified, mainly consisting of sesqui and monoterpenes. Individual plants and botanical families exhibited extensive chemical variations in their EO composition. Probabilistic models demonstrated that qualitative and quantitative differences contribute to chemical diversity, depending on the botanical family. The EOs exhibited antimicrobial biocidal activity against pathogenic bacteria, fungi and multiple predicted pharmacological targets. Our results demonstrate the antimicrobial potential of EOs from rainforest plants, indicate novel macromolecular targets, and contribute to highlighting the chemical diversity of native species.

Chemical Composition and Evaluation of Insecticidal Activity of Seseli bocconei Essential Oils against Stored Products Pests

In this study, the chemical composition of the essential oils (EOs) obtained from different aerial parts (flowers, leaves, and stems) of Seseli bocconei Guss., a wild species endemic of Sicily, was investigated. Furthermore, the EOs' biocidal effects towards two pests of stored products, Sitophilus oryzae and Callosobruchus maculates, were evaluated. This activity was evaluated in Petri dish bioassays to establish the survival rate of adults treated with the EOs comparing them with solvent and a commonly used insecticide (pyrethrum). The data obtained from the toxicity bioassay evidenced that stems' EOs and leaves' EOs have a contact/fumigation effect towards the two insect species tested, while the EOs from the flowers did not exhibit a different mortality than the solvent. The EOs from the stem and leaves of S. bocconei, tested at 10 mg/petri dish, determined a LT50 of 53.38 and 42.97 h, respectively, on S. oryzae adults, and of 45.23 and 42.97 h, respectively, on C. maculatus adults. The promising bioactivity of S. bocconei leaves' EOs and stems' EOs toward S. oryzae and C. maculatus is encouraging in the perspective to test these oils and their main constituents for further experiments in the laboratory and field.

Pesticidal Activities of Callicarpa and Premna Essential Oils From Vietnam

Mosquito-borne diseases are a consistent problem in Vietnam. Additionally, freshwater snail species are agricultural pests and are known to be intermediate hosts for several parasitic worms. There is a need for new and complementary botanical pesticidal agents for controlling these pests and essential oils have shown promise. In this work, essential oils from 2 species of Callicarpa ( C. rubella and C. sinuata) and 4 species of Premna ( P. chevalieri, P. corymbosa, P. maclurei, and P. tomentosa) were screened for mosquito larvicidal activity against Aedes albopictus and Culex quinquefasciatus and for molluscicidal activity against 3 freshwater snail species, Gyraulus convexiusculus, Pomacea canaliculata, and Tarebia granifera. Callicarpa rubella essential oil showed exceptional larvicidal activity against Cx. quinquefasciatus with 24-h LC50 of 9.8 μg/mL. In addition to C. rubella, the essential oils of P. chevalieri and P. tomentosa showed notable molluscicidal activities against P. canaliculata with LC90 values ≤ 20 μg/mL. These Callicarpa and Premna essential oils were all rich in sesquiterpenes and should be considered for continued investigation as botanical pesticidal agents.