Phytochemical and Larvicidal Evaluation of Vernonia Glaberrima Welw. Ex O. Hoffm. (Asteraceae) Leaves on Aedes Mosquito Larvae
Sabastine Obinna Onugwu 1, Adaeze Linda Onugwu 2*, Christopher Obodike Ezugwu 3
- Department of Pharmacognosy, Enugu State University of Science and Technology, Agbani, Enugu State.
- Department of Pharmaceutics, University of Nigeria Nsukka, Enugu State.
- Department of Pharmacognosy & Environmental Medicine, University of Nigeria, Nsukka, Enugu State
| Key words:
Vernonia glaberrima, larvacidal activity, Aedes aegypti, Phytochemical
*Corresponding author: adaeze.onugwu@unn.edu.ng; Page No: 81-90 |
AbstractMalaria, a parasitic infection transmitted by the anopheles mosquito, poses a significant global health threat especially in the tropical regions. Larvicidal agents can be used to kill the larva of the mosquito before they grow into adult. This study investigated the larvicidal activity of Vernonia glaberrima on Aedes mosquito larva. The leaves of Vernonia glaberrima were collected, macroscopically examined, dried and pulverized. Extraction of the pulverized leaf was done by cold maceration using methanol. Fractionation of the methanol extract was carried out via Column chromatography using n-hexane, ethyl acetate and aqueous methanol. Larvicidal assay was done using WHO method. Vacuum liquid chromatography was performed on aqueous methanol fractions with dichloromethane: methanol solvent system. Thin-layer chromatography was performed to pool the aqueous methanol sub-fractions to four sub-fractions. The larvicidal activity study was repeated on the aqueous methanol sub-fractions. The fractions were evaluated using GC-MS analysis to identify the constituents. The macroscopic evaluation reveals green leaves with characteristic smell, smooth texture and bitter taste. The secondary metabolites present in the leaves of Vernonia glaberrima were flavonoids, steroids, saponins, alkaloids, glycosides, terpenoids, phenols, hydrogen cyanide and tannins. The quantitative phytochemical screening showed relatively high concentrations of tannins (13.3 mg/g), phenol (12.7 mg /g) and flavonoids (9.9 mg/g), moderate amounts of alkaloids (6.4 mg/g), glycosides (5.1 mg/g) and terpenoids (5.6 mg/g), while saponins (0.6 mg/g), steroids (0.4 mg/g) and hydrogen cyanide (0.4 mg/g) were relatively low. All the fractions were effective against larvae of Aedes aegypti. Aqueous methanol fraction was the most efficacious with LC50 of 2.807 whereas methanol fraction was the least efficacious with LC50 of 25.876. Sub-fraction 3 of aqueous methanol fraction showed 75 % larvicidal activity. Many compounds including 2, 4-Di-tert-butylphenol, Gamma-terpinene and 14-Octadecenoic acid were identified by the GS-MC analysis. This study shows that the leaves of Vernonia glaberrima have potent larvicidal activity which can be harnessed for the control of malaria.
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