The toxicity of materials derived from the seed of Pongamia pinnata to third instars of insecticide-susceptible Culex pipiens pallens and Aedes aegypti and wild Aedes albopictus was examined using a direct contact bioassay. Results were compared with those of the currently used insecticides fenthion and temephos. The active principles of Pongamia pinnata were identified as the karanjin (1), karanjachromene (2), pongamol (3), pongarotene (4), oleic acid (5), and palmitic acid (6) by spectroscopic analysis. Based on 24 h LC50 values, karanjin (14.61 and 16.13 mg/L) was the most toxic compound, followed by oleic acid (18.07 and 18.45 mg/L) and karanjachromene (18.74 and 20.57 mg/L). These constituents were less toxic than either fenthion (LC50, 0.0031 and 0.0048 mg/L) or temephos (0.021 and 0.050 mg/L) against Ae. aegypti and Cx. p. pallens. Low toxicity was produced by pongamol (LC50, 23.95 and 25.76 mg/L), pongarotene (25.52 and 37.61 mg/L), and palmitic acid (34.50 and 42.96 mg/L). Against A. alpopictus instars, oleic acid (LC50, 18.79 mg/L) was most toxic. Low toxicity was observed with the other five constituents (LC50, 35.26- 85.61 mg/L). P. pinnata seed-derived active principles, particularly karanjin, karanjachromene, and oleic acid, merits further study as potential mosquito larvicides for the control of mosquito populations in light of global efforts to reduce the level of highly toxic synthetic larvicides in the aquatic environment.

The toxicity of imperatorin (1) and osthol (2) identified in Cnidium monnieri seed and four structurally related compounds to third instar larvae of insecticidesusceptible (KS-CP strain) and field-collected (DJ-CP colony) of Culex pipiens pallens was examined. Results were compared with those of to conventional mosquito larvicide, fenitrothion and temephos. Based on 24-h LC50 values, imperatorin was 1.9, 3.7, 4.2, 12.4, and 15.1 times more toxic than isopimpinellin, isoimperatorin, osthole, xanthotoxin, and bergapten against KS-CP larvae, respectively. Overall, these compounds were less toxic than either fenitrothion or temephos. However, these compounds did not differ in toxicity against larvae from the two Culex strains, even though the DJ-CP larvae exhibited high levels of resistance α-cypermethrin, deltamethrin, chlorpyrifos, fenthion, and chlorfenapyr (resistance ratio, 94-1179). This finding indicates that the isolated compounds and the pyrethroid, organophosphorus, and pyrrole insecticides do not share a common mode of action or elicit cross-resistance.