Location: Subtropical Horticulture ResearchTitle: Bioassay-guided isolation and identification of Aedes aegypti larvicidal and biting deterrent compounds from Veratrum lobelianum
|Ali, Zulficar - University Of Mississippi|
|Bernier, Ulrich - Uli|
|Nalbantsoy, Ayse - Ege University|
|Khan, Ikhlas - University Of Mississippi|
|Ali, Abbas - University Of Mississippi|
Submitted to: Open Chemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/6/2018
Publication Date: 4/24/2018
Citation: Tabanca, N., Ali, Z., Bernier, U.R., Epsky, N.D., Nalbantsoy, A., Khan, I.A., Ali, A. 2018. Bioassay-guided isolation and identification of Aedes aegypti larvicidal and biting deterrent compounds from Veratrum lobelianum. Open Chemistry. 16(1):324-332. https://doi.org/10.1515/chem-2018-0030.
Interpretive Summary: Plants are a good source of natural compounds that are used for insect control, and plants in the genus Veratrum, which are members of the lily family, have been found to contain many different classes of biologically active chemicals. Ethanol extracts of Veratrum lobelianum rhizomes were found to be mosquito larvicides and to deter biting by mosquito adults. Therefore, scientists from SHRS, CMAVE and University of Mississippi conducted research using bioassay-guided fractionation of V. lobelianum extracts to identify the larvicidal and deterrent compounds, and to evaluate identified compounds for other biological activity. Five compounds were identified by spectroscopic techniques. Of these, beta-sitosterol displayed the greatest larvicidal activity, with two compounds (resveratrol and oxyresveratrol) showing both larvicidal and biting deterrent activity. Although compounds in the same chemical class have been shown to have biological effects on both insects and on human cells, no further biological activity was found in tests of resveratrol and oxyresveratrol. Bioassay-guided fractionation was an effective technique to identify chemicals responsible for the larvicidal and deterrent activity of the ethanol extract of Veratrum lobelianum, and use of this technique will aid in the discovery of new biologically active natural products from plants.
Technical Abstract: An ethanol extract from Veratrum lobelianum Bernh. rhizomes was evaluated for biting deterrent and larvicidal activity against Aedes aegypti. V. lobelianum extract showed larvicidal activity with LC50 values of 11.79 ppm and 89.9 ppm against 1st and 4th instar larvae, respectively, at 24 h post-treatment. The extract also showed proportion not biting (PNB) value of 0.76 at 100 ug/cm2 against females of Ae. aegypti. Systematic bioassay-guided fractionation of V. lobelianum extract resulted in the isolation of five compounds that were identified as ethyl linoleate (1), ethyl palmitate (2), beta-sitosterol (3), resveratrol (4) and oxyresveratrol (5) by GC-MS, 1H-NMR, and 13C-NMR techniques, comparison with literature data, and confirmation with authentic compounds. Compound 1 exhibited larvicidal activity with an LC50 value of 24.1 (22.0-26.2) ppm whereas 2 was inactive. Beta-sitosterol (3) displayed the highest larvicidal activity with LC50= 1.7 (1.3-2.3) ppm and LC90= 5.1 (3.4-13.8) ppm. The stilbenoids, 4 (trans-resveratrol) and 5 (oxyresveratrol) had larvicidal activity with LC50 values of 18.5 (15.3-22.3) and 22.6 (19.0-26.8) ppm, respectively, and equivalent PNB values of 0.75 at 25 nmol/cm2. In addition, 4 and 5 were explored for their human-based repellency against Ae. aegypti, attractiveness against male medflies Ceratitis capitata, and also evaluated against series of human carcinoma cells (A549, HEK293, HeLa, SH-SY5Y); however, no significant activity was found.