According to Folin-Dennis method (15), 1.0 mL of sample was added to
dimethyl sulfoxide (DSMO) in 7.0 mL of distilled water and 0.5 mL of Folin-Dennis reagent.
After 3 min, 1.0 mL of saturated sodium carbonate (NaCO3) solution and 0.5
mL of distilled water were added.
The absorbance was measured by UV/Vis spectrophotometer at 725 nm.