Bioassay-guided isolation of insect repellent compounds from Ligusticum porteri root extract

Authors: ALI, ABBAS - University Of Mississippi; Tabanca, Nurhayat; ALI, ZULFIQAR - University Of Mississippi; DEMIRCI, BETUL - Anadolu Universtiy; KHAN, IKHLAS - University Of Mississippi

Submitted to: ACTA TROPICA
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/16/2024
Publication Date: 9/6/2024
Citation: Ali, A., Tabanca, N., Ali, Z., Demirci, B., Khan, I.A. 2024. Bioassay-guided isolation of insect repellent compounds from Ligusticum porteri root extract. ACTA TROPICA. https://doi.org/10.1016/j.actatropica.2024.107386.
DOI: https://doi.org/10.1016/j.actatropica.2024.107386

Interpretive Summary: Mosquitoes are important in global public health because of their ability to transmit diseases including malaria, filariasis, yellow fever, dengue, and other viral infections. Many synthetic chemicals have insecticidal and/or repellent effects that are used to control vectors and protect human populations from vector-borne diseases. However, since some synthetic chemicals have adverse effects of synthetic insecticides on the environment and human health, attention has turned to developing biodegradable and non-toxic compounds from plants. Therefore, scientists at the USDA-ARS Subtropical Horticulture Research Station, University of Mississippi, and Turkey, collaborated to identify deterrent compounds from Ligusticum porteri root extract against the yellow fever mosquito, Aedes aegypti. In the isolation steps, only one of the four fractions showed activity. Subsequently, the active fraction has been used for the isolation and identification of active natural deterrents. Further, fractionation was carried out by preparative thin-layer chromatography and purified active compounds n-butylidenephthalides such as (Z)-3-butylidenephthalide and (E)-3-butylidenephthalide. In vivo direct skin application bioassay demonstrated that (E/Z)-3-butylidenephthalide standard is a good candidate for commercial insect repellent development studies.

Technical Abstract: In our natural products screening program for mosquitoes, ethanolic extract of roots of Ligusticum porteri Coult. & Rose showed high repellency. Systematic bioassay-guided fractionation of the extract was performed to identify the active repellent compounds. In K & D bioassay, (Z)-3-butylidenephthalide, (E)-3-butylidenephthalide and mixture of (E/Z)-3-butylidenephthalide showed biting deterrent activity similar to N,N-Diethyl-3-methylbenzamide (DEET) against Aedes aegypti (L.). In the A & K bioassay, MED values were similar whereas the values of the mixtures of (E/Z)-3-butylidenephthalide with carotol was lower (6.25 + 6.25 = 12.5 µg/cm2) than individual treatments (25 µg/cm2). In direct skin application bioassay, (E/Z)-3-butylidenephthalide showed excellent repellency. The residual repellency of (E/Z)-3-butylidenephthalide at 8 and 16% application rates was 4.5 and 10-h respectively which was equal or better than DEET with residual time of 5 and 9-h, respectively. The mixture of (E/Z)-3-butylidenephthalide with carotol (8 + 8%) increased the residual repellency by 2-h (44%) as compared to (E/Z)-3-butylidenephthalide alone at a dose of 8%. This data indicated that (E/Z)-3-butylidenephthalide is an effective mosquito repellent that is stable and has a long shelf life. The activity of this compound is extraordinary and residual time is comparable to DEET. In vivo data demonstrated an enormous potential of (E/Z)-3-butylidenephthalide as a repellent that can be developed for commercial use. However, (E)-3-butylidene phthalate was not found in the L. porteri essential oil, but (E)-3-butylidene phthalate was < 1% in the oil.