Essential oils are promising as environmentally friendly and safe sources of pesticides for human use. Furthermore, they are also of interest as aromatherapeutic agents in the treatment of Alzheimer’s disease, and inhibition of the enzyme acetylcholinesterase (AChE) has been evaluated as an important mechanism. The essential oils of some species in the genera Callicarpa, Premna, Vitex and Karomia of the family Lamiaceae were evaluated for inhibition of electric eel AChE using the Ellman method. The essential oils of Callicarpa candicans showed promising activity, with IC₅₀ values between 45.67 and 58.38 μg/mL. The essential oils of Callicarpa sinuata, Callicarpa petelotii, Callicarpa nudiflora, Callicarpa erioclona and Vitex ajugifolia showed good activity with IC₅₀ values between 28.71 and 54.69 μg/mL. The essential oils Vitex trifolia subsp. trifolia and Callicarpa rubella showed modest activity, with IC₅₀ values of 81.34 and 89.38, respectively. trans-Carveol showed an IC₅₀ value of 102.88 µg/mL. Molecular docking and molecular dynamics simulation were performed on the major components of the studied essential oils to investigate the possible mechanisms of action of potential inhibitors. The results obtained suggest that these essential oils may be used to control mosquito vectors that transmit pathogenic viruses or to support the treatment of Alzheimer’s disease.

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.

Mosquitoes, in addition to being a biting nuisance, are vectors of several pathogenic viruses and parasites. As a continuation of our work identifying abundant and/or invasive plant species in Vietnam for use as ecologically friendly pesticidal agents, we obtained the essential oils of Blumea lacera, Blumea sinuata, Emilia sonchifolia, Parthenium hysterophorus, and Sphaeranthus africanus; analyzed the essential oils using gas chromatographic techniques; and screened the essential oils for mosquito larvicidal activity against Aedes aegypti and Aedes albopictus. The most active larvicidal essential oils were B. sinuata, which was rich in thymohydroquinone dimethyl ether (29.4%), (E)-β-caryophyllene (19.7%), α-pinene (8.8%), germacrene D (7.8%), and α-humulene (4.3%), (24-h LC₅₀ 23.4 and 29.1 μg/mL) on Ae. aegypti and Ae. albopictus, respectively, and Emilia sonchifolia, dominated by 1-undecene (41.9%) and germacrene D (11.0%), (24-h LC₅₀ 30.1 and 29.6 μg/mL) on the two mosquito species. The essential oils of P. hysterophorus and S. africanus were also active against mosquito larvae. Notably, B. sinuata, P. hysterophorus, and S. africanus essential oils were not toxic to the non-target water bug, Diplonychus rusticus. However, E. sonchifolia essential oil showed insecticidal activity (24-h LC₅₀ 48.1 μg/mL) on D. rusticus. Based on these results, B. sinuata, P. hysterophorus, and S. africanus essential oils appear promising for further investigations.

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 LC_50-aegypti of 0.96 and 0.40 µg/mL while 24 h LC_{50-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.

The chemical composition of leaf essential oil of the harmful invasive species Chromolaena odorata collected in Vietnam was analyzed by GC/MS and chiral GC. All three essential oil samples (O1, O2 and O3) in this study fell into chemotype I characterized by α-pinene/geigerene/germacrene D/(E)-β-caryophyllene from a total of six different chemotypes. Chemotype I demonstrated larvicidal effects against Aedes aegypti (Linnaeus, 1762), Aedes albopictus Aedes albopictus (Skuse, 1894), Culex fuscocephala (Theobald, 1907) and Culex quinquefasciatus (Say, 1823), with 24 h LC₅₀ values ranging from 11.73 to 69.87 µg/mL. In contrast, its microemulsion formulation exhibited enhanced toxicity, yielding 24 h LC₅₀ values between 11.16 and 32.43 µg/mL. This chemotype also showed repellent efficacy against Ae. aegypti, with protection times ranging from 70.75 to 122.7 min. Fumigant toxicity was observed against Aedes aegypti, with LC₅₀ values of 40.27% at 0.5 h and 0.34% at 24 h. Molluscicidal activity was recorded with 48 h LC₅₀ values between 3.82 and 54.38 µg/mL against Indoplanorbis exustus (Deshayes, 1833), Pomacea canaliculate (Lamarck, 1822), Physa acuta (Draparnaud, 1805). Additionally, the chemotype exhibited acetylcholinesterase inhibitory activity, with an IC₅₀ value of 70.85 µg/mL. Antimicrobial potential was also demonstrated, with MIC values ranging from 2.0 to 128.0 µg/mL against Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Salmonella enterica, and Candida albicans. The C. odorata essential oil can be considered as a potential bioresource for human health protection strategies.

Resistance to synthetic insecticides has intensified the search for plant-derived biopesticides. Pilea plataniflora C.H.Wright (Urticaceae), a medicinal plant native to Vietnam and China, has a high essential oil yield; however, its essential oil composition and biological activities remain unreported. This study characterized the chemical composition and evaluated the pesticidal and antimicrobial activities of P. plataniflora essential oil collected across three successive years. Chemical composition was determined by GC-MS. Pesticidal activities (larvicidal, repellent, fumigant adulticidal, and molluscicidal) were evaluated following modified WHO guidelines, and antimicrobial activity was assessed by broth microdilution. Three oil samples from the same population showed considerable chemical variation. The 2018 sample (PP18) was dominated by δ-3-carene (44.1%), α-thujene (20.1%), and sabinene (7.2%). The 2019 sample (PP19) comprised δ-3-carene (15.9%), (E)-β-caryophyllene (12.2%), and β-pinene (10.6%). The 2020 sample (PP20) was dominated by δ-3-carene (26.8%), sabinene (11.6%), and terpinen-4-ol (5.5%). All samples exhibited larvicidal activity against mosquito species tested. PP19 and PP20 showed repellent effects against Aedes aegypti (Linnaeus, 1762), with protection times of 133.3±18.8 and 264.8±72.5 min at 50% concentration, respectively. PP19 showed the greatest fumigant adulticidal potency (60-min LC₅₀ = 2.98%). PP18 exhibited antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, and Candida albicans (MIC: 32-128 µg/mL). This first report on P. plataniflora essential oil demonstrates that this species is a promising source of bioactive compounds with larvicidal, repellent, fumigant, and antimicrobial properties relevant to sustainable vector management and infection control.