Sesquiterpene Hydrocarbon-rich Essential Oil from Teucrium viscidum Blume and its Antimicrobial and Mosquito Larvicidal Activities

Objectives This study aimed to investigate the essential oil extracted from the aerial parts of Teucrium viscidum Blume, a perennial herb belonging to the Lamiaceae family, collected in Vietnam. The focus was on determining the essential oil's chemical composition and evaluating its antimicrobial and mosquito larvicidal activities. Methods The essential oil of T. viscidum was analyzed using GC–FID/MS to identify its chemical constituents. The antimicrobial activity was assessed against seven microorganisms using the broth microdilution method to determine minimum inhibitory concentration (MIC) and half-maximal inhibitory concentration (IC 50 ) values. The larvicidal activity was evaluated against Culex quinquefasciatus larvae, with lethal concentration (LC 50 and LC 90 ) values calculated after 24 and 48 h of exposure. Results Chemical analysis revealed that the essential oil of T. viscidum was predominantly composed of sesquiterpene hydrocarbons, with ( E)-caryophyllene (47.91%) and germacrene D (19.17%) as the major constituents. The essential oil exhibited significant antimicrobial activity against three Gram-positive bacteria ( Enterococcus faecalis, Staphylococcus aureus, and Bacillus cereus), one Gram-negative bacterium ( Pseudomonas aeruginosa), and one yeast ( Candida albicans), with MIC values ranging from 32 to 64 μg/mL and IC 50 values ranging from 9.56 to 24.07 μg/mL. The mosquito larvicidal activity of the essential oil showed strong efficacy against C. quinquefasciatus larvae, with LC 50 values of 23.07 μg/mL after 24 h and 19.67 μg/mL after 48 h, and LC 90 values of 32.90 μg/mL at 24 h and 29.99 μg/mL at 48 h, indicating increased effectiveness with prolonged exposure. Conclusion This study provides a comprehensive analysis of the chemical composition and biological activities of T. viscidum essential oil. The findings highlight its potent antimicrobial and mosquito larvicidal properties, suggesting it as a promising natural alternative to synthetic antimicrobial agents and insecticides. Further research is warranted to explore its mechanisms of action and potential applications in pharmaceuticals and pest control.