Essential Oils of The Leaves of Syzygium hemilamprum (F. Muell.) Craven & Biffin.: Chemical Analysis, Antimicrobial, Mosquito Larvicidal, ADMET, and Molecular Docking Studies

Chemical constituents from essential oil and n-hexane extract of S hemilamprum leaves were first identified. The obtained essential oil was dominated by monoterpene hydrocarbons (71.55%), and their oxygenated derivatives (20.2%), in which β-pinene (31.5%), limonene (19.4%), α-pinene (12.3%), and α-terpineol (7.4%) were the principal agents. The n-hexane extract was characterized by monoterpene hydrocarbons (42.2%) and non-terpenic compounds (34.0%) with β-pinene (32.8%), and n-hexadecane (10.2%) being the major compounds. Both two samples showed antimicrobial activity against the Gram (+) bacterium Staphylococcus aureus ATCC 6538, the Gram (-) bacterium Pseudomonas aeruginosa ATCC 9027, and the yeast Saccharomyces cerevisiae ATCC 2601 with the same MIC value of 128 µg/mL. Remarkably, they strongly inhibited mosquito larvicidal activity against Aedes aegypti and Culex quinquefasciatus larvae with the LC50 and L90 values of less than 20 µg/mL for 24 and 48 h treatments. A molecular docking study suggested limonene and α-terpineol as potent inhibitors of the mosquito odorant binding protein. In silico study on the physicochemical and ADMET properties of the main components of essential oils was also conducted.