Abstract
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.
Highlights
Gomphrena spp. are edible, ornamental and medicinal plants commonly known as Globe Amaranth or Bachelor Button
The flowers of Gomphrena globosa L. have medicinal potential because they are rich in bioactive compounds such as betacyanins, betalaines and flavonoids
This flower has been studied by some researchers, who had identified phenolic compounds such as hydroxycinnamic acids and flavonoids [1], being kaempferol-3-O-(6-rhamnosyl) hexoside and kaempferol-3-O-hexoside the main compounds determined in decoction extracts [2]
Summary
Gomphrena spp. are edible, ornamental and medicinal plants commonly known as Globe Amaranth or Bachelor Button. There are many reports about different extraction methods for edible flowers such as Soxhlet [3,4], ultrasonics [4], supercritical fluid extraction [5] and solid phase microextraction [6]. These methods are based on an appropriate selection of solvent and energy input to increase chemical solubility and mass transfer rate [7]; high energy consumption, long extraction times and relatively low extraction yields can be observed [8]. High pressures (HP) have been recently applied to extract bioactive ingredients from plant materials [8, 9], taking advantage of time saving, higher
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