A 100 μL aliquot of methanolic extracts was
mixed with 900 μL of Folin–Ciocalteu phenol reagent (diluted 1:10
with water) and was allowed to stand for 5 min at room temperature;
0.75 mL of 7% sodium bicarbonate solution was added to
the mixture and vortexed for 30 s, and allowed to stand for 90 min at
room temperature.