The authors acknowledge the Portuguese Foundation for Science and Technology (FCT,
Portugal) for the financial support provided by the research grant SFRH/BD/95853/2013 and
FCT/MEC for the financial support to QOPNA research Unit (FCT UID/QUI/00062/2013)
and REQUIMTE (UID/QUI/50006/2013) through national funds and when applicable cofinanced
by the FEDER, within the PT2020 Partnership Agreement.
The present study aimed to compare the influence of different extraction solvents (water, methanol, water:acetone (6:4, v/v)), methods (heating (37 °C, 30 min) or high pressure (HP) (300 or 500 MPa) and extraction time (7.5 or 15 min)) on flavonoids, hydrolysable tannins and antioxidant activity (Total Reducing Capacity (TRC), DPPH Free Radical Scavenging Activity and Reducing Power) of Gomphrena globosa L. flower extracts. The water:acetone extracts obtained by heating had the highest values of flavonoids, hydrolysable tannins and antioxidant activity. When applying HP, variable results were obtained. Still, the
application of HP to water allowed to extract more hydrolysable tannins, as well as to obtain extracts with higher antioxidant activity than with heating, but no significant alterations were observed with methanol. In conclusion, both solvent and extraction method influence the content of bioactive compounds, being HP treatment a promising method to obtain enriched aqueous extracts in line with the principles of green-chemistry.
