Florets (5 g) were homogenized (Homogenizer Ultra-Turrax,
T25, IKA, China) with 20 mL of methanol and centrifuged at
4 C (Sigma 4K 15, USA) at 2500 g for 20 min. Then, 20 mL of
supernatant was added to 1.58 mL of water and 100 mL of
FolineCiocalteu (0.4 mol/L).