Structure-Activity Relationship Studies on the Mosquito Toxicity and Biting Deterrency of Callicarpenal Derivatives
MISSISSIPPI UNIV UNIVERSITY
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Callicarpenal 13,14,15,16-tetranorclerod-3-en-12-al1S,2R,4aR,8aR-1,2,3,4,4a,7,8,8a-octahydro-1,2,4a,5-tetramethylnaphthalen-1-ylacetaldehyde 1 has previously demonstrated significant mosquito bite-deterring activity against Aedes aegypti and Anopheles stephensi in addition to repellent activity against host-seeking nymphs of the blacklegged tick, Ixodes scapularis. In the present study, structural modifications were performed on callicarpenal 1 in an effort to understand the functional groups necessary for maintaining andor increasing its activity and to possibly lead to more effective insect control agents. All modifications in this study targeted the C12 aldehyde or the C3 alkene functionalities or combinations thereof. Mosquito biting deterrency appeared to be influenced most by C3 alkene modification as evidenced by catalytic hydrogenation that resulted in a compound having significantly less effectiveness than 1 at a test amount of 25 nmolcm2. Oxidation andor reduction of the C12 aldehyde did not diminish mosquito biting deterrency, but, at the same time, none of the modifications were more effective than 1 in deterring mosquito biting. Toxicities of synthesized compounds towards Ae. aegypti ranged from an LD50 value of 2.36 to 40.11 mg per mosquito. Similarly, LD95 values ranged from a low of 5.59 to a high of 104.9 mg.
- Agricultural Chemistry