Insecticidal toxicities of naphthoquinone and its structural derivatives

Abstract

Insecticidal toxicities of bioactive constituent from Diospyros kaki roots and its structural derivatives were evaluated against the larvae of Aedes aegypti, Culex pipiens pallens, and Ochlerotatus togoi. Bioactive constituent of D. kaki roots was isolated by some chromatographic methods and identified as 5-hydroxy-2-methyl-1,4-naphthoquinone. Based on the LC50 values of 5-hydroxy-2-methyl-1,4-naphthoquinone structural derivatives, 2,3-dichloro-5,8-dihydroxy-1,4-naphthoquinone (0.89, 0.80, and 1.04 μg/mL) had the most potent insecticidal activity, followed by 2,3-dibromo-1,4-naphthoquinone (1.32, 1.28, and 1.94 μg/mL), 5,8-dihydroxy-1,4-naphthoquinone (3.57, 3.34, and 5.04 μg/mL), 2,3-dichloro-1,4-naphthoquinone (4.76, 3.89, and 5.33 μg/mL), 5-hydroxy-2-methyl-1,4-naphthoquinone (5.66, 5.43, and 6.09 μg/mL), and 2,2′-bi(3-hydroxy-1,4-naphthoquinone) (33.93, 32.82, and 36.17 μg/mL) against Ae. aegypti, Cx. pipiens pallens, and Oc. togoi, respectively. In this regard, 5-hydroxy-2-methyl-1,4-naphthoquinone and its structural derivatives could be suitable as insecticidal agents to control the larvae of the three mosquito species.