Bioassay-guided isolation of iridoid glucosides from Stenaria nigricans, their biting deterrence against aedes aegypti (Diptera: Culicidae) and repellency potential against imported fire ants (Hymenoptera: Formicidae)

Authors: ZULFIQAR, FAZILA - University Of Mississippi; ALI, ABBAS - University Of Mississippi; ALI, ZULFIQAR - University Of Mississippi; KHAN, IKHLAS - University Of Mississippi

Submitted to: Molecules
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/17/2022
Publication Date: 10/19/2022
Citation: Zulfiqar, F., Ali, A., Ali, Z., Khan, I.A. 2022. Bioassay-guided isolation of iridoid glucosides from Stenaria nigricans, their biting deterrence against aedes aegypti (Diptera: Culicidae) and repellency potential against imported fire ants (Hymenoptera: Formicidae). Molecules. https://doi.org/10.3390/molecules27207053.
DOI: https://doi.org/10.3390/molecules27207053

Interpretive Summary: The causative agent for many human diseases such as dengue fever, yellow fever, Rift Valley fever, malaria, Zika, chikungunya, and West Nile are mosquito transmitted pathogens. The use of insect repellents such as DEET (N,N-diethyl-3-methylbenzamide), a standard among the series, significantly reduces mosquito bites, effectively reducing disease transmission. New environmentally friendly alternatives for mosquito management, particularly from natural sources, are crucially needed. Stenaria nigricans, the main species of the genus Stenaria, is prevalent in central and northern Mexico and central, eastern, and the southwestern United States. In our natural product screening program against mosquitoes, hundreds of in-house plant extracts were screened randomly for biting-deterrent activity against Aedes aegypti L. A S. nigricans extract showed significant biting deterrent activity, which prompted us to investigate its chemical constituents. Seven iridoid glucosides, including four previously undescribed ones were isolated from the methanol extract of S. nigricans. This study reports the isolation and characterization of seven iridoid glucosides and their biting deterrent activity against yellow fever mosquito, Ae. aegypti and repellency against hybrid imported fire ants. A few of the compounds showed biting deterrence against Ae. aegypti comparable to DEET and have the potential to be used as repellents against mosquitoes.

Technical Abstract: Mosquitoes transmitted pathogens cause human diseases such as dengue fever, yellow fever, Rift Valley fever, malaria, Zika, chikungunya, and West Nile that affect a large population of the world. The methanolic extract of Stenaria nigricans aerial parts showed significant biting deterrence, similar to DEET, against Aedes aegypti. Four undescribed iridoid glucosides together with three previously reported ones were isolated through mosquito-biting deterrent bioassay-guided chemical investigation of the methanolic extract of Stenaria nigricans aerial parts. Structure elucidation was achieved by sophisticated NMR (1D and 2D) and mass spectral data analysis. Undescribed metabolites were characterized as stenigrosides A-D (1-4) while known compounds were identified as asperuloside, deacetylasperuloside, and daphylloside. Based on biting deterrence index (BDI) values, the isolated compounds showed biting deterrence similar to DEET. The pure compounds did not show repellency at the concentration of 125 µg/g against hybrid imported fire ants.