Premna Species in Vietnam: Essential Oil Compositions and Mosquito Larvicidal Activities

Essential oils have emerged as viable alternatives to synthetic insecticides for control of mosquito-borne pathogens. The leaf essential oils of eight species of Premna (Lamiaceae) growing in central Vietnam have been obtained by hydrodistillation and analyzed by gas chromatography–mass spectrometry. Sesquiterpene hydrocarbons dominated most of the Premna essential oils, with the notable exception of Premna mekongensis from Ngoc Linh Nature Reserve, which had α-pinene as the major component. Larvicidal activities against Aedes aegypti have been determined and all of the Premna essential oils showed larvicidal activity with 24-h LC(50) < 65 μg/mL. The leaf essential oils of Premna cambodiana from Chu Mom Ray National Park and Premna mekongensis from Ngoc Linh Nature Reserve showed the best larvicidal activities with 24-h LC(50) of 16.8 and 18.0 μg/mL, respectively. The essential oil compositions and larvicidal activities of P. cambodiana, Premna flavescens, Premna maclurei, P. mekongensis, and Premna puberula are reported for the first time. Although the larvicidal activities of Premna leaf essential oils are promising, the essential oil yields are relatively low (0.10–0.25%).