Abstract

This research was performed in order to compare the water and acetone extracts of raw and boiled for 10, 20, 40 and 60 min Korean lotus roots (KLR) and Polish white onion (PWO) in the contents of theirbioactive compounds, antioxidant activity and thermostability. It was found that polyphenols (mg GAE/g), flavanols (mg GAE/g), flavonoids (mg CE/g), anthocyanins(mg CGE/kg) and tannins (mg CE/g) in water extract of raw lotus roots were 14.18 0.7, 8.41 0.5, 1.09 0.06, 21.3 1.2 and 7.29 0.4, and of white onion e 11.11 0.6, 6.78 0.3, 0.71 0.03, 17.00 0.9 and 1.64 0.08, respectively, and significantly higher in KLR (P < 0.05). The antioxidant activity of raw KLR water extract (139.4 6.1, 53.1 3.6 and 89.3 4.6 mmol TE/g for DPPH, CUPRAC and ABTS, respectively) was significantly higher than in white onion (23.84 1.8, 31.9 2.1 and 38.14 2.6 for DPPH, CUPRAC and ABTS, respectively, P < 0.05). The thermostability of the water KLR extract's of polyphenols, flavanols, flavonoids, anthocyanins and tannins was high and even after 60 min of boiling remains as 40.0, 42.3, 50.5, 41.4 and 41.0%, respectively. After 60 min of boiling the most thermostable compounds were flavonoids e remaining at 50.5% in water extract of KLR. Also after 60 min of boiling the thermostability of the antioxidant activity of water extracts of KLR remained significantly high: 40.6, 42.3, 46.3 and 43.6%, according to DPPH, FRAP, ABTS and CUPRAC assays, respectively. Similar relationshipwas obtained with acetone extracts, but the valuewas lower thanwith thewater ones. In conclusion, the contents of some bioactive compounds, the antioxidant activity and the thermostability in water and acetone extracts of KLR are significantly higher than the sameindices inPWO. FTIR and fluorimetrycan be used as additional markers for the characterization of bioactive compounds in vegetables.

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Authors (9)