Briefly,
25 lL of each sample and standards were transferred into appropriate
wells of a 96-well plate in triplicate, mixed with 125 lL of
10-fold freshly diluted Folin–Ciocalteu phenol reagent, allowed to
react for 10 min, and then added 125 lL of 7.5% sodium carbonate
(w/v), incubated for 60 min prior to measuring the absorbance at
765 nm using a UV/Vis microplate reader against a reagent blank
(EL 340, Bio-Tek Instruments Inc., Winooski, VT, USA).