Mosquitoes are important vectors of several diseases, and control of these insects is imperative for human health. Insecticides have proven useful in controlling mosquito populations, but insecticide resistance and environmental concerns are increasing. Additionally, emerging and re-emerging microbial infections are problematic. Essential oils have been shown to be promising mosquito larvicidal agents as well as antimicrobial agents. In this work, the essential oils from four species of Myrtaceae (Baeckea frutescens, Callistemon citrinus, Melaleuca leucadendra, and Syzygium nervosum) growing wild in central Vietnam have been obtained by hydrodistillation and analyzed by gas chromatographic techniques. The essential oils have been screened for mosquito larvicidal activity against Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus, and for antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, and Candida albicans. Callistemon citrinus fruit essential oil, rich in α-pinene (35.1%), 1,8-cineole (32.4%), limonene (8.2%), and α-terpineol (5.8%) showed good larvicidal activity with 24-h LC 50 = 17.3 µg/mL against both Ae. aegypti and Cx. quinquefasciatus, and good antibacterial activity against E. faecalis (minimum inhibitory concentration (MIC) = 16 µg/mL) The 48-h larvicidal activities of M. leucadendra leaf essential oil, rich in α-eudesmol (17.6%), guaiol (10.9%), linalool (5.1%), (E)-caryophyllene (7.0%), and bulnesol (3.6%) were particularly notable, with LC 50 of 1.4 and 1.8 µg/mL on Ae. aegypti and Cx. quinquefasciatus. Similarly, M. leucadendra bark essential oil, with α-eudesmol (24.1%) and guaiol (11.3%), showed good antibacterial activity against. E. faecalis. Both B. frutescens and C. citrinus leaf essential oils demonstrated anti-Candida activities with MIC values of 16 µg/mL. The results of this investigation suggest that essential oils derived from the Myrtaceae may serve as "green" alternatives for the control of mosquitoes and/or complementary antimicrobial agents.

The leaf, stem, and floral essential oils of Crassocephalum crepidioides growing wild in central Vietnam were obtained by hydrodistillation and analyzed by gas chromatography-mass spectrometry. The major component in all 3 oils was myrcene (59.3%, 26.1%, and 43.3%, respectively). The 24-hour mosquito larvicidal activities of the oil of the aerial parts (stems and leaves) were determined against wild-caught Aedes albopictus (IC 50 = 14.3 μg/mL), laboratory-reared Aedes aegypti (IC 50 = 4.95 μg/mL), and wild-caught Culex quinquefasciatus (IC 50 = 18.4 μg/mL). The high concentration of myrcene in the essential oil likely accounts for the mosquito larvicidal activity observed.

Mosquito-borne infections are a constant problem in Vietnam, and mosquito vector control is a primary approach to control these infections. Essential oils represent environmentally friendly alternatives to synthetic pesticides for mosquito control. The essential oils of two weedy species in Vietnam, Erechtites hieraciifolius and E. valerianifolius, have been obtained by hydrodistillation and analyzed by gas chromatography–mass spectrometry. The essential oils have been screened for mosquito larvicidal activity against Aedes albopictus, Ae. aegypti, and Culex quinquefasciatus. The essential oil from the aerial parts of E. hieraciifolius was rich in α-pinene (14.5%), limonene (21.4%), and caryophyllene oxide (15.1%), while E. valerianifolius essential oil was dominated by myrcene (47.8%) and α-pinene (30.2%). Both essential oils showed good larvicidal activity against Ae. albopictus (24-h LC50 10.5 and 5.8 μg/mL, respectively) and Ae. aegypti (24-h LC50 10.6 and 12.5 μg/mL, respectively). The essential oil of E. valerianifolius also showed good activity against Cx. quinquefasciatus larvae (24-h LC50 = 40.7 μg/mL). Thus, Erechtites essential oils may serve as low-cost vector control agents for mosquito-borne infections.

The Lauraceae is a family rich in aromatic and medicinal plants. Likewise, essential oils derived from members of this family have demonstrated a myriad of biological activities. It is hypothesized that members of the Lauraceae from Vietnam will yield essential oils that may be useful in controlling mosquito populations and treating microbial infections. In this work, the leaf essential oils of eleven species of Lauraceae (Beilschmiedia erythrophloia, B. robusta, B. yunnanensis, Cryptocarya concinna, C. impressa, C. infectoria, Litsea viridis, Machilus balansa, M. grandifolia, Neolitsea ellipsoidea, and Phoebe angustifolia) have been obtained by hydrodistillation and the chemical compositions analyzed by gas chromatography – mass spectrometry (GC-MS) and gas chromatography with flame ionization detection (GC-FID). The essential oils were screened for larvicidal activity against Aedes aegypti, Ae. albopictus, and Culex quinquefasciatus, and for antimicrobial activity against Enterococcus faecalis, Staphylococcus aureus, Bacillus cereus, Escherichia coli, Pseudomonas aeruginosa, Salmonella enterica, and Candida albicans. The leaf essential oil of N. ellipsoidea, rich in (E)-β-ocimene (87.6%), showed excellent larvicidal activity against Ae. aegypti with a 24 h LC50 of 6.59 μg/mL. The leaf essential oil of C. infectoria, dominated by germacrene D (55.5%) and bicyclogermacrene (11.4%), exhibited remarkable larvicidal activity against Cx. quinquefasciatus (48 h LC50 = 0.40 μg/mL). N. ellipsoidea leaf essential oil also demonstrated notable antibacterial activity against E. faecalis and B. cereus with minimum inhibitory concentration (MIC) values of 16 μg/mL, while the leaf essential oil of C. impressa showed excellent anticandidal with an MIC of 16 μg/mL. Leaf essential oils from the Lauraceae should be considered for utilization as alternative agents for controlling mosquito populations and as antimicrobial agents.