Supercritical carbon dioxide extraction of Trigonella foenum-graecum L. seeds: Process optimization using response surface methodology

•Extraction of diosgenin by supercritical extraction on a wide range of condition parameters was examined.•Procedure of diosgenin isolation from fenugreek including pretreatment of plant and SCE was applied and described.•Influence of pressure, temperature and amount of CO2 on diosgenin extraction was determined.•Optimization of supercritical extraction of diosgenin was examined.