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Title: Identification of the mosquito biting deterrent constituents from the Indian folk remedy plant Jatropha curcas

Author
item Cantrell, Charles
item ALI, ABBAS - University Of Mississippi
item Duke, Stephen
item KHAN, IKHLAS - University Of Mississippi

Submitted to: Journal of Medical Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/10/2011
Publication Date: 7/6/2011
Citation: Cantrell, C.L., Ali, A., Duke, S.O., Khan, I. 2011. Identification of the mosquito biting deterrent constituents from the Indian folk remedy plant Jatropha curcas. Journal of Medical Entomology. 48(4):836-845.

Interpretive Summary: An investigation of the Indian folk remedy plant, Jatropha curcas, was performed to specifically identify the constituents responsible for the mosquito repellency of the oil as a whole. Jatropha curcas seed oil is burned in oil lamps in India and part of Africa to repel biting insects, primarily mosquitoes. Identified constituents, both free fatty acids and triglycerides, were evaluated for activity in Aedes aegypti biting deterrent assays. We have demonstrated that both free fatty acids and triglycerides present in J. carcus oil possess Ae. aegypti repellent activity and are responsible for the reported biting deterrent activity of the oil as a whole. Specifically, oleic, palmitic, linoleic, and stearic acids were all highly effective at repelling Ae. aegypti mosquitoes. Oleic, palmitic, and linoleic acids were also all more active than stearic acid in the same bioassay. Evaluation of the triglycerides containing each of these fatty acids revealed that tripalmitin, tristearin, trilinolein, and triolein all demonstrated significant activity whereas tripalmitin was the most active. This is the first literature report on the A. aegypti repellency of triglycerides.

Technical Abstract: An investigation of the Indian folk remedy plant, Jatropha curcas, was performed to specifically identify the constituents responsible for the mosquito biting deterrent activity of the oil as a whole. Jatropha curcas seed oil is burned in oil lamps in India and part of Africa to repel biting insects, primarily mosquitoes. The seed oil was thoroughly analyzed by 1H NMR, 13C NMR, HPLC-RI, and GC-FID to identify the constituents in the oil. Identified constituents, both free fatty acids and triglycerides, were evaluated for activity in Aedes aegypti biting deterrent assays. Furthermore, an oil condensation trap was used to demonstrate that free fatty acids or triglycerides are partially volatilized during the combustion process. These compounds were found to be responsible for the biting deterrency of the burned oil. Specifically, oleic, palmitic, linoleic, and stearic acids were all active at 25 nmoles/cm2 above that of solvent control in Aedes aegypti biting deterrent assays. Oleic, palmitic, and linoleic acids were all more active than stearic acid in the same bioassay. Evaluation of the triglycerides containing each of these fatty acids revealed that tripalmitin, tristearin, trilinolein, and triolein all demonstrated significant activity above a solvent control at 10 ug/cm2, whereas tripalmitin was the most active. Due to literature reports suggesting insecticidal activity of the oil, J. curcas seed oil and its free fatty acid constituents were also evaluated against 1-day old Ae. aegypti larvae up to 500 ppm. Oleic acid was the only fatty acid having larvicidal activity against 1-day old Ae. aegypti larvae with an LC50 of 47.9 ppm.