A comparison between supercritical fluid and pressurized liquid extraction methods for obtaining phenolic compounds from Asparagus officinalis L

Supercritical fluid and pressurized liquid extractions are investigated for effective recovery of phenolic compounds from asparagus. By the one hand, the effect of different co-solvents on supercritical fluid extraction (SFE) is examined. Results confirm that the presence of water and ethanol is essential to obtain a phenolic enriched extract with high antioxidant activity. Operative conditions influence the extraction yield, whereas the phenolic composition of the extract does not vary significantly. By the other hand, the differences among various solvents on pressurized liquid extraction (PLE) is analysed. Once again, the mixture water-ethanol gives the best results in terms of phenolic content, which are comparable with SFE and Soxhlet ones. In total, 14 phenolic derivatives were identified, being rutin the most abundant compound in all the extracts. Phenolic acids, mainly 3-O-feruloylquinic acid, represent a relevant percentage of the phenolic content of the asparagus extracts. The methods and solvents considered influence diversely the extraction of molecules with different structure.