First Report on the Chemical Profile and Biological Effects of the Essential Oil From <i>Cratoxylum formosum</i> (Jack) Benth. &amp; Hook.f. ex Dyer Collected in Vietnam

Cratoxylum formosum (Jack) Benth. & Hook.f. ex Dyer is a medicinal plant widely distributed in Southeast Asia. This study presents the first investigation of the essential oil from leaves of C. formosum collected in Vietnam, focusing on its chemical composition, antimicrobial activity, and mosquito larvicidal potential. Gas chromatography-flame ionization detection (GC-FID)/mass spectrometry (MS) analysis identified 35 compounds in the essential oil, with (E)-caryophyllene (39.30%), α-humulene (12.90%), and (E)-β-ocimene (11.85%) as the major constituents. The essential oil exhibited notable antimicrobial activity against Staphylococcus aureus, Enterococcus faecalis, Bacillus cereus, Pseudomonas aeruginosa, and Candida albicans, with minimum inhibitory concentration (MIC) values ranging from 16 to 64 µg/mL and IC₅₀ values between 7.55 and 20.56 µg/mL. Larvicidal assays demonstrated strong activity against Aedes aegypti, Aedes albopictus, and Culex quinquefasciatus, with LC₅₀ values ranging from 44.27 to 77.71 µg/mL and LC₉₀ values from 57.74 to 102.61 µg/mL after 24 and 48 h of exposure. These findings suggest that C. formosum essential oil is a promising natural source of antimicrobial and mosquito control agents.