The flavonoid content was determined according to Eberhardt,
Lee, and Liu (2000), and expressed as mg of catechin equivalent
(CE) per kg of d.m. Briefly, 75 mL of 5 g/100 g NaNO2 solution was
mixed with 100 mL of the extract and 1.4 mL of distilled water. After
6 min, 150 mL of 10 g/100 g AlCl3 solution was added to form a
flavanoidealuminum complex. After 7 min, 500 mL of 1 mol/L NaOH
was added, and after 10 min the mixture was centrifuged at
9000g for 5 min. Absorbance of the supernatant was measured at
510 nm.