Total phenolic content (TPC) was measured using the Folin–Ciocalteu
colorimetric method described previously (Wojdylo et al.,
2007). Sample extracts prepared for total phenolic content
(100 ll), were mixed with 0.2 ml of Folin–Ciocalteu reagent and
2 ml of distilled water, and then incubated at room temperature
for 3 min. Following the addition of 1 ml of 20% sodium carbonate
to the mixture, total polyphenols were determined after 1 h of
incubation at room temperature. The absorbance of the resulting
blue colour was measured at 765 nm with a spectrophotometer
(Shimadzu UV–1240). Quantification was done with respect to
the standard curve of gallic acid (r2 = 0.9985). The results were
expressed as gallic acid equivalents (GAE), milligrams per 100 g
of dry matter (dm). All determinations were performed in triplicate
(n = 3).