Larvicidal activity of the active constituent isolated from Tabebuia avellanedae bark and structurally related...

Mosquito larvicidal activities of active constituent isolated from Tabebuia avellanedae bark and its structurally related derivatives were examined against the fourth instar larvae of Aedes aegypti, Culex pipiens pallens, and Ochlerotatus togoi. The insecticidal constituent of T. avellanedae bark was isolated by chromatographic techniques and identified as 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthalenedione. On the basis of the 50% lethal concentration (LC50) values against C. pipiens pallens larvae, the most toxic compound was 1,4-naphthalenedione (1.26 mg/L), followed by 1,2-naphthalenedione (1.43 mg/L), 1,4-naphthalenediol (3.20 mg/L), 2-chloro-3-pyrrolidino-1,4-naphthalenedione (5.11 mg/L), 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthalenedione (8.30 mg/L), and 2-chloro-3-morpholino-1,4-naphthalenedione (12.98 mg/L). Similar results against A. aegypti and O. togoi larvae were observed for 2-hydroxy-3-(3-methyl-2-butenyl)-1,4-naphthalenedione and its derivatives. According to the LC50 values against three mosquito species, these compounds were less toxic than pirimiphos-methyl. Nonetheless, naturally occurring T. avaellenedae bark-derived materials could be useful as a natural mosquito control agent.