Production and Characterization of a Mosquito Repellent Coil Using Neem (AZADIRACHTA INDICA): FTIR, UV-VIS Analysis and Bioassay Evaluation

Abstract

This study explores the production and characterization of a mosquito repellent coil formulated using neem (Azadirachta indica) leaf extract. The coil was prepared using plant-based ingredients including starch, sawdust, flour, and charcoal, with neem extract serving as the active repellent agent. Fourier Transform Infrared (FTIR) spectroscopy was used to assess the phytochemical profile, revealing functional groups including O–H, C–H, C=O, and C–O, which are typically associated with bioactive neem compounds. These groups were also detected in the final coil, suggesting that the active constituents remained intact after formulation. UV-Visible spectrophotometric analysis showed a strong absorption peak at approximately 220 nm in both the neem extract and the coil, with absorbance values of 4.0 and 3.0, respectively. This indicates that key light-absorbing compounds such as azadirachtin were partially preserved during formulation. A laboratory bioassay was conducted on Culex mosquitoes to evaluate repellent efficacy. Seventy-five adult mosquitoes, divided into three replicates of 25, were exposed to the coil. Mortality increased progressively over time, reaching 24 to 25 dead mosquitoes per replicate at 24 hours. The mean mortality was 24.67 ± 0.58, representing a 98.7% mortality rate. Additionally, the median lethal dose (LD₅₀) calculated using Karber’s method was 96.7%, further confirming the high potency of the coil formulation. The findings highlight neem’s effectiveness as a natural insecticidal agent and support its application in environmentally friendly mosquito control solutions.