naphthoquinones and pirimiphos-methyl

The objective of this study was to determine the larvicidal activity of an active compound isolated from Cercis chinensis heartwood and its structurally related analogs against 4th-stage Aedes aegypti, Culex pipiens pallens, and Ae. togoi. The larvicidal compound of C. chinensis was isolated with the use of various chromatographic techniques and identified as analogs of 1,4-naphthalenedione. Based on the median lethal concentration (LC(50)) values of commercially procured analogs against Ae. aegypti larvae, the most toxic analog was 2-bromo-1,4-naphthalenedione (1.19 µg/ml); followed by 5-hydroxy-1,4-naphthalenedione (1.72 µg/ml); 2-methyl-1,4-naphthalenedione (9.12 µg/ml); 2-hydroxy-1,4-naphthalenedione (10.76 µg/ml); and 2-methoxy-1,4-naphthalenedione (12.50 µg/ml). Similar results were observed against Cx. p. pallens and Ae. togoi larvae with 1,4-naphthalenedione analogs. These results also showed that 1,4-naphthalenedione analogs were less toxic than the organophosphate pirimiphos-methyl. Nonetheless, naturally occurring C. chinensis-derived materials and 1,4-naphthalenedione analogs have potential for development as mosquito larvicidal agents.

Topics: Aedes; Animals; Culex; Fabaceae; Insecticides; Larva; Lethal Dose 50; Mosquito Control; Naphthoquinones; Organothiophosphorus Compounds; Plant Extracts; Species Specificity; Structure-Activity Relationship; Wood