Structure-activity relationship of unsaturated fatty acids as mosquito ovipositional repellents

Abstract

Various straight-chain unsaturated fatty acids from C14 to C24 were evaluated for their ovipositional repellency against gravid females of the southern house mosquitoCulex quinquefasciatus Say, and the relationship between the structures of the fatty acids and their ovipositional repellency was determined. A double bond withZ configuration was prerequisite for an unsaturated fatty acid to be highly repellent;E isomers were less active or even inactive. No relationship was found between the repellency and the number of double bonds in the unsaturated fatty acids. In C18 monounsaturated fatty acids, (Z)-9 acid was more active than (Z)-11 and (Z)-6 acids, indicating that a double bond at the 9 position rendered an acid highly repellent. Among (Z)-9-alkenoic acids of different chain lengths, the most repellent was C18 acid which was also more active than (Z)-11-C20, (Z)-13-C22, and (Z)-15-C24 acids. Oleic[(Z)-9-octadecenoic]acid, which met all these criteria, was the most ovipositionally repellent among the unsaturated fatty acids tested.

Behavioral and electrophysiological responses of Culex quinquefasciatus to certain fatty acid esters

“…These short chain esters contain phenyl ring in their structure which are volatile and aromatic in nature that attract more gravid mosquitoes for oviposition than high molecular weight straight chain fatty acid esters used in this study. Females of C. quinquefasciatus experienced 100% repellence from C 5 to C 12 fatty acids at 10 −2 M concentration , and exhibited positive ovipositional response to trans-octadec-11-enoic acid at concentration below 1 × 10 −3 M, relative to control Hwang et al (1984). However, in our study esters synthesized from C 5 to C 12 fatty acids with corresponding alkyl halides also repelled Culex females from oviposition in the treated bowls.…”

The Ancient Chemistry of Avoiding Risks of Predation and Disease

“…Our hypothesis that repellency reflects the degree of unsaturation was rejected. Hwang et al (1984) made a similar conclusion for mosquito oviposition repellents. For woodlice, linolenic acid (three double bonds) was not significantly repellent whereas oleic (one double bond) and linoleic acid (two double bonds) were highly repellent (P \ 0.05).…”

Volatile and Semivolatile Compounds in Gray Catbird Uropygial Secretions Vary with Age and Between Breeding and Wintering Grounds

“…Oleic acid was a minor component in the secretions we analyzed and did not load significantly onto any of the principal components, making evaluation of its role difficult. Interestingly, in a comparison of C14 to C24 unsaturated carboxylic acids, oleic acid was the most effective ovipositional repellant in Culex quinquefasciatus (Hwang et al, 1984). Oleic acid is sometimes called the "smell of death" because of its role as a molecule that signals death in arthropods thereby eliciting an avoidance behavior (Yao et al, 2009).…”