2.7. Analysis of total phenolic compounds (TPC)
The content of TPC in extracts was determined with Folin–
Ciocalteu reagent (Folin & Ciocalteu, 1927). A calibration curve
was prepared by using 1 ml reference gallic acid solutions in ethanol (0.025, 0.075, 0.100, 0.175 and 0.350 mg/ml), which were
mixed with 5 ml of a standard Folin–Ciocalteu reagent and diluted
with distilled water (1:10) and 4 ml of 7.5% sodium carbonate solution in distilled water. The absorption was read after 30 min at
765 nm. The concentration of TPC was expressed in mg of gallic
acid equivalents (GAE) per g of plant extract. The TPC was calculated by the following formula:c=cV/m, where cis the concentration of gallic acid, determined form the calibration curve (mg/
ml);Vis the volume of plant extract (100 ml); mis the weight of
pure plant extract (g).