Larvicidal activity of tectoquinone isolated from red heartwood-type Cryptomeria japonica against two mosquito species

Mosquito larvicidal activities of methanolic extracts from different plant parts of red heartwood-type Cryptomeria japonica D. Don against the fourth-instar larvae of Aedes aegypti and Aedes albopictus were examined. Results of mosquito larvicidal tests demonstrated that the n-hexane fraction of C. japonica sapwood methanolic extract had an excellent inhibitory effect against the larvae of A. aegypti and A. albopictus and its LC₅₀ values were 2.4 and 3.3 μg/ml, respectively, in 24 h. Following the bioactivity-guided fractionation procedure, the active constituent isolated from C. japonica sapwood was characterized as tectoquinone by spectroscopic analyses. The LC₅₀ values of tectoquinone against A. aegypti and A. albopictus in 24 h were 3.3 and 5.4 μg/ml, respectively. In addition, comparisons of mosquito larvicidal activity of anthraquinone congeners demonstrated that anthraquinone skeleton with a methyl group at C-2 position, such as tectoquinone, exhibited the strongest mosquito larvicidal activity. Results of this study show that the methanolic extract of C. japonica sapwood may be considered as a potent source and tectoquinone as a new natural mosquito larvicidal agent.