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

• SFE and PLE are competitive methods to obtain phenolic-rich extracts from asparagus.
• The presence of water–ethanol mixture enhances the phenolic content of the extracts.
• SFE extraction yield is significantly affected by the presence of liquid water.
• Different methods and solvents are selective towards different phenolic compounds.
• The highest antioxidant activity was obtained by SFE with water–ethanol as co-solvent.

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.

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