Optimization of Thermal and Temporal Parameters in Ethanol-Assisted Soxhlet Extraction of Bioactive Drugs: A Kinetic Comparison of Eugenol and Caffeine

Abstract

In this study, the temperature and time parameters for the extraction process of pharmaceutical compounds using a Soxhlet apparatus with ethanol as a solvent were optimized, comparing the kinetics of the compounds (eugenol) from clove buds and (caffeine) from dried Arabica coffee beans. A second-order kinetic model was used, and the effects of temperature (60-75 degrees Celsius), extraction time, and the solute-to-solvent ratio on the mass transfer coefficient KL were studied. The results showed that the efficiency of extracting eugenol compound increased significantly with the rise in temperature, reaching an optimal kL value of 0.019319 min⁻¹ at 75 degrees Celsius due to the decrease in solvent viscosity, which led to increased molecular movement, as shown by the results, longer extraction times improved kL, although solvent saturation effects appeared after 6 hours. Conversely, caffeine extraction peaked near ethanol's boiling point at 75°C (kL​ = 0.004546 min⁻¹), with the solute-to-solvent ratio critically influencing yield—a 1:3 ratio achieved the highest efficiency. The mass transfer coefficient (kL​) exhibited a near-linear relationship with both temperature and time, confirming its dominance in extraction efficiency. The second-order model elucidated both processes, demonstrating that temperature (75°C), time (6 hours), and solute-to-solvent ratio (1:3) enhance caffeine yield, offering significant insights for the augmentation of bioactive compound extraction in the pharmaceutical and industrial domains. Subsequent investigations may examine alternate solvents or hybrid methodologies.