Application of response surface methodology to optimise supercritical carbon dioxide extraction of essential oil from Cyperus rotundus Linn.

► SC-CO2 extracted essential oils from Cyperus rotundus. ► Effects factors were investigated by response surface methodology. ► The oil yield was represented with central composite rotatable design. ► Pressure and CO2 flow rate are the main effects factors. ► Oil yield of C. rotundus was significantly higher than that of Soxhlet extraction.