Bioassay guided isolation of mosquito biting deterrent compounds from Strumpfia maritima

BACKGROUND In our natural products screening program against mosquitoes, we screened ethanolic extract of Strumpfia maritima Jacq. which showed high biting deterrent activity in Klun and Debboun (K&D) bioassays against Aedes aegypti L. Through bioguided fractionation we isolated six compounds from the active fractions. The extract and pure compounds were evaluated for larvicidal and biting deterrent activity against Aedes aegypti. RESULTS Ethanolic extract with proportion not biting (PNB) value of 0.8 ± 0.08 provided biting deterrent activity similar to N,N‐dimethyl‐m‐toluamide (DEET) (PNB = 0.9 ± 0.05) against Ae. aegypti. Five out of eight fractions, prepared through bioassay‐guided fractionation, showed biting deterrent activity similar to DEET. Six compounds were isolated from active fractions and characterized as squalene, ursolic acid, betulonic acid, cabraleone, ursolic acid acetate, and 27‐p‐E‐coumaroyloxyursolic acid. The biting deterrent activity of ursolic acid acetate (biting deterrence index, BDI = 0.85), cabraleone (BDI = 0.79), and ursolic acid (BDI = 0.78) was similar to DEET against Ae. aegypti. Strumpfia maritima extract did not show larvicidal activity at the highest screening dose of 125 ppm in the larvicidal bioassay. CONCLUSION The ethanolic extract and pure compounds showed biting deterrent activity against Ae. aegypti. The high biting deterrent activity of ursolic acid acetate and cabraleone indicated a great potential for these natural compounds to be developed as mosquito repellents. © 2020 Society of Chemical Industry The ethanolic extract and isolated compounds showed biting deterrent activity against Aedes Aegypti, which could have a great potential for these natural compounds to be developed as mosquito repellents.