Extraction of pelargonium radula leaves by green technology supercritical carbon dioxide for mosquito repellent

This study investigates the potential of the aromatic plant Pelargonium radula (P. radula) as a natural mosquito repellent, specifically targeting Aedes aegypti (A. aegypti). Despite its promising properties, P. radula remains underutilized in repellent formulations. To address this, the study focuses on applying green extraction technology—specifically, Supercritical Fluid Extraction (SFE) using the SFT-100 system from Supercritical Fluid Technologies. The SFE was employed as an alternative to conventional extraction methods to overcome challenges such as thermal degradation, limited durability, and environmental impact. P. radula leaves were extracted at various temperatures (40–60 °C) and pressures (200–450 bar), using a constant CO₂ flow rate of 24 mL/min for 60 minutes. The goal was to determine the optimal pressure and temperature conditions for maximizing extraction yield. Additionally, the solubility of P. radula extract in supercritical carbon dioxide (SC-CO₂) was analyzed based on the data collected. The extracts were then characterized using Fourier-Transform Infrared Spectroscopy (FTIR) and Gas Chromatography–Mass Spectrometry (GC-MS) to confirm the presence of mosquito-repellent compounds, particularly effective against A. aegypti. The optimal extraction conditions were found to be 400 bar and 60 °C. Under these conditions, the increased density and solvating power of SC-CO₂ enhanced penetration into the plant matrix and improved mass transfer of target compounds. The solubility of P. radula extract in SC-CO₂ was determined to be 0.0315 mg/g CO₂, indicating a strong interaction between solute and solvent under high-pressure, high-temperature conditions. The FTIR and GC-MS analyses confirmed the presence of bioactive compounds such as citronellol, geraniol, and 10-epi-γ-eudesmol—known for their mosquito-repellent properties. Overall, this study demonstrates that the SFE is an effective and eco-friendly method for extracting high-value, plant-based mosquito repellents from P. radula, without the risk of thermal degradation or solvent contamination.