Determination of total flavonols
The content of total flavonols was determined following the Yermakov method (Mickelsen & Yamamoto 1958). Rutin hydrate (Sigma Aldrich, purity ≥ 94%) was used as standard solution. Briefly, 200 μL of sample or rutin standard was mixed with 200 μL AlCl3 (20 g L-1 in ethanol, Sigma Aldrich) and 600 μL sodium acetate (50 g L-1; Sigma Aldrich). Samples and standards were incubated at 20 °C for 2.5h, and absorbance measured at 440 nm using a spectrophotometer (Agilent Technologies, Cary Series 100 UV-VIS Spectrophotometer, Italy). Results were expressed as µmol rutin equivalent.