Total phenolic content (TPC) was determined using the Folin-
Ciocalteu (F-C) method (Waterhouse, 2003). To prepare a calibra-
tion curve, solutions of gallic acid at concentrations from 0 to
200 mg/L were used. The R2 coefficient of a standard curve was
0.9920. The following components were added to 7 mL tubes: 40 mL
of calibration solution, sample or blank; 3.16 mL of distilled water;
200 mL of F-C reagent. The components were then mixed. After 30 s
600 mL of 20% sodium carbonate was added. The solution was left at
room temperature for 1 h. Absorbance was measured at 765 nm
against a blank (0 mL solution) using a Cecil CE2041 spectropho-
tometer (Cecil Instruments Limited, Cambridge, UK). The poly-
phenolic leaf extract samples were diluted five-fold. Results were
expressed as mg of gallic acid per gram [mg GAE/g].