Supercritical extraction of salicin, aspirin precursor, from the willow bark, laboratory optimization via response surface methodology and mathematical modeling

Abstract

In this study, salicin, the key active ingredient in willow bark and a primary source of aspirin, was extracted using supercritical CO₂. Gas chromatography (GC) characterized the extract. Key operating factors, including pressure, temperature, particle size, and extraction time, were varied to optimize extraction yield, employing response surface methodology (RSM) with a central composite design (CCD) method. The maximum yield was 12.371 % (mass of extracted salicin / mass of dry willow bark) with a 56.75 % salicin recovery under the optimal condition, determined as 22 MPa pressure, 40 °C temperature, 0.45 mm particle size, and 100 minutes extraction time. Results showed that higher extraction time and pressure increased yield, while temperature and particle size reduced it. Extraction time had the most significant effect, while temperature was the least impactful. The Sovová and Tan and Liou models were applied, showing close agreement between predicted and experimental extraction curves.