Larvicidal Evaluation against Aedes aegypti and Antioxidant and Cytotoxic Potential of the Essential Oil of Tridax procumbens L. Leaves

The present study evaluated the antioxidant, cytotoxic, and larvicidal potential of the essential oil of Tridax procumbens leaves, as well as identified the compounds present in the essential oil. The antioxidant activity was evaluated by the sequestration method of 2,2-diphenyl-1-picrylhydrazyl radical, the cytotoxic activity was evaluated using Artemia salina, the larvicidal bioassay was performed with larvae in the third stage of development of the Aedes aegypti mosquito, and the identification of the metabolites was performed by gas chromatography coupled to the mass spectrometer (GC-MS). The phytochemical oil analysis showed the presence of 20 compounds, with thymol and γ-terpinene being the main ones. It presented antioxidant activity with an IC50 of 194.51 μg mL−1, demonstrating antioxidant activity in the highest concentrations tested. It presented low cytotoxic activity against A. salina, with an LC50 of 1238.67 μg mL−1, demonstrating atoxicity in the concentrations tested. The essential oil presented good larvicidal activity when compared to the literature, with an LC50 = 79.0 μg mL−1 in 24 hours and LC50 of 69.15 μg mL−1 in 48 hours. In this way, it was possible to identify that the essential oil of the leaves of T. procumbens presented potential for the development of a natural larvicide, as well as antioxidant activity satisfactory to the radical DPPH and low toxicity to A. salina.

Nanoinsecticidal Efficacy of Ag/Ni Bimetallic Nanoparticles (BMNPs) on Lymphatic Filariasis Vector

Aims: Nanoparticles are gradually gaining wide scientific interest due to their various applications in catalysis, magnetism, medicine, optics, as antibacterial and nanolarvicidal agents. This research aimed at evaluating the larvicidal activity of green synthesized Ag/Ni BMNPs from the aqueous root extract of Borassus aethiopum as the stabilizing agent as well as their spectroscopic investigation using UV-Visible and FT-IR spectroscopy. Place and Duration of Study: The study was conducted in Gombe State University between August and December, 2019. Methodology: In this study, Ag/Ni hybrid bimetallic nanoparticles was synthesized using an eco-friendly method from the secondary metabolites of Borassus aethiopum acting as the reducing agent. Results: Optical measurements using UV-Vis showed the maximum absorption wavelength at 410nm while the FT-IR result for the root extract showed peaks at 3443.26cm-1, 2929.48 cm-1, 1651.28 cm-1, and 1080.12 cm-1 corresponding to OH stretch, sp3 C-H stretch, C=C stretch and C-O-C stretching respectively. These were replaced in the spectra of the BMNPs with the absence and appearance of some others indicating that they were involved in the capping process. The lethal concentration (LC50) was found to be 5.730, 13.585 and 15.735 mg/L for 1st, 2nd and 3rd/4th instars respectively. Also, the lethal concentration (LC90) was found to be 88.444, 195.689 and 236.889 mg/L for 1st, 2nd and 3rd/4th instars respectively. Conclusion: The larvicidal bioassay result showed a dose-dependent mortality rates against Culex quinquefasciatus larvae which suggest they can be developed to control the insect population.

Assessment of the Larvicidal Efficacy of the Hexane-Leaf-Extracts of Selected Tropical Plant Species

The proliferation of mosquito vector in tropical countries has increased the prevalence of malaria with high morbidity and mortality burden. This research is concerned with the biolarvicidal efficacies of Cassia alata, Microdesmis puberula¸ and Spilanthes filicaulis extracted with hexane solvent, and screened against mosquito larva. Results on the negative control had no mortality on the larvae compared to the positive control, which had total mortality (p<0.05). The C. alata plant extracts was the most active with LC50 value of 25.26 ppm, followed by; M. puberula (32.83 ppm), and S. filicaulis (36.46 ppm). Based on the outcome of the larvicidal bioassay, Hexane-leaf-extracts of all plants can be recommended for the formulation of biolarvicide due to their efficacies.