Optimization of supercritical carbon dioxide pretreatment of Flaveria bidentis leaves prior extraction of sulfated flavonoids with subcritical water

Flaveria bidentis is an invasive plant containing Sulfated Flavonoids (SFs) with therapeutic potential. The extraction of these compounds would add value to the biomass generated during weeding. This work reports the optimization of the pretreatment of F. bidentis leaves with supercritical CO₂ (P-SC-CO₂) prior extraction of these compounds using subcritical water extraction. The combined effect of different levels of the three factors on P-SC-CO₂, Time, Pressure and Depressurization rate, was investigated with Response Surface Methodology. The optimal pretreatment conditions were as follows: Time = 30 min, Pressure = 30 MPa and Depressurization rate = 2 kg CO₂/h. Under these conditions, 72.45 ± 0.99 mg of totals SFs/100 g of leaves was recovered, practically doubling total SFs extraction yield in the absence of pretreatment. In addition, the structural damage caused by P-SC-CO₂ on the leaves was detected using Scanning Electron Microscopy.