2.3.1. Total phenolic compounds (TPC)

The total phenolic content (TPC) values of both samples were measured with Folin–Ciocalteu’s test using gallic acid (GA) as standard (Singleton et al., 1999). Briefly, 20 µL of six different propolis extracts, standard samples dilutions (from 0.500 mg/mL to 0.015 mg/ml), and 0.2 N 400 µL Folin reagents were mixed and completed to 5.0 mL with distilled water, and then vortexed. After 3 min incubation, 400 µL of Na₂CO₃(10%) was added and incubated at 25 °C. The absorbance was measured at 760 nm after 2-h incubation. The TPC was expressed in mg GAE/mL using a standard curve.