The toxicity of Asarum heterotropoides root steam distillate compounds to third instar larvae of Culex pipiens pallens, Aedes aegypti, and Ochlerotatus togoi (formerly Aedes togoi) was examined using a direct contact mortality bioassay. Results were compared with those following the treatment with fenthion and temephos. A. heterotropoides root steam distillate exhibited good larvicidal activity (21.07-27.64 ppm), based on LC50 values. Potent activity was produced by safrole (LC50, 8.22-16.10 ppm), terpinolene (11.85-15.32 ppm), -terpinene (12.64-17.11 ppm), (–)-β-pinene (12.87-18.03 ppm), (+)-limonene (13.26-24.47 ppm), 3-carene (13.83-19.19 ppm), and α-phellandrene (13.84-23.08 ppm), although the larvicidal activity of these compounds was less toxic than either fenthion (LC50, 0.023-0.029) or temephos (0.016-0.020). A. heterotropoides root steam distillate and its constituents described merit further study as potential mosquito larvicides for protection from humans and domestic animals from vector-borne diseases and nuisance caused by mosquitoes.

In view of the recently increased interest in developing plant-origin insecticides are an alternative to chemical insecticides. This study was undertaken to assess the larvicidal potential of the two (H52C1 and H5C) compounds from Asarum sieboldii Miq. against dengue vector Aedes aegypti. Among the two compounds, compound I (H52C1) was most active than the compound II (H5C) against third instar larvae of Ae. aegypti. The LC50 value of the compound I was 2.03 (95% CL, 1.51-2.76) and the compound II was 10.66 (95% CL, 9.23-12.42). These findings would be useful in promoting research aiming at the development of new agents for mosquito larval control based on bioactive chemical compounds from plant origin.