Multistage fractionation of pine bark by liquid and supercritical carbon dioxide

Multistage fractionation of pine bark was performed using subcritical and supercritical CO₂ at increasing pressures and temperatures. In total, seven fractions were collected, which demonstrated different enrichments of families of compounds. In particular, subcritical CO₂ yielded 41% of the total extract in which unsaturated fatty acids represented the most abundant family. The subsequent five supercritical steps increased the recovery of sterol esters, wax esters and resin acids at higher temperatures and pressures, reaching 80% of the total extractable mass. In the last step, using ethanol as a co-solvent, an additional 20% of extract was recovered, which was enriched with phenolics and glycerol. A full characterisation of the extracts was accomplished by high-temperature GC-MS/FID using four internal standards, which were representative of the main classes of compounds contained in the pine bark extract.