engleski

Extraction of total flavonoids from barley grain using high-temperature/high-pressure reactor

This work examined the influence of extraction temperature (90 180 °C), solvent concentration (36-90 % aqueous ethanol) and time (30-90 min) on the extractability of total flavonoids and on the antioxidant activity of extracts from three samples of barley grains. Barley samples were collected from three silos at different locations of Croatia: Nova Gradiška (BNG), Čakovec (BC) and Vinkovci (BV), and represent an average harvest of barley in 2011/2012. Extractions were performed using high- temperature/high-pressure reactor and optimal extraction conditions determined using response surface methodology (RSM) by Box Behnken design. The total flavonoids content (TF) was measured using the aluminium chloride colorimetric assay at 510 nm and results were expressed as (+) catechin equivalent per a dry basis of barley grain (mgCE/gdb). Antioxidant activity of barley extract was evaluated by spectrophotometric method (515 nm) against stable 2.2 diphenil-1-picryhydrazyl radical (DPPH•) and results were expressed as antiradical power (ARP, gDPPH•/Lextract). Based on RSM analysis, temperature was the most significant (p < 0.05) factor affecting the TF and optimum conditions for flavonoids extraction were 180 °C, 36 % aqueous ethanol, and 90 minutes. At these conditions, the predicted values of TF in extracts of BNG, BC and BV were 5.25 mgCE/gdb, 5.31 mgCE/gdb and 4.47 mgCE/gdb, respectively. High positive correlation (R > 0.88) between TF and ARP of tested barley extracts was observed, which suggest that the flavonoids contribute to the overall antioxidant activity of barley extracts.

high-temperature/high-pressure extraction; optimization of extraction; response surface methodology; barley; total flavonoids

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