. Total phenolic content
Total phenolic content (TPC) of extracts was determined using
the Folin–Ciocalteu assay. Samples (300 l l) were introduced into
test tubes followed by 1.5 ml of Folin–Ciocalteu’s reagent (10 times
dilution) and 1.2 ml of sodium carbonate (7.5% w/v). The tubes
were allowed to stand for 30 min before absorbance at 765 nm
was measured. TPC was expressed as gallic acid equivalent (GAE)
in mg/100 g material. The calibration equation for gallic acid was
y = 0.0111x ? 0.0148 (R 2 = 0.9998) where y is the absorbance and
x is the concentration of gallic acid in mg/l.