The total content of phenolic compounds of the different extracts was determined
by the colorimetric Folin–Ciocalteu method with slight adaptation as described
by Sato et al. (1996). Briefly, samples of the obtained extracts were
diluted in ethanol and pipetted into 96-well plates. Next, Folin–Ciocalteu reagent
and sodium carbonate were added to each well. The mixture was incubated for
2 h at room temperature in the dark. The blue color that developed was measured
using a microtitre plate reader. Gallic acid was used for calibration. The phenolic
content of the extracts is expressed in gallic acid equivalent (GAE) concentration
(mg/mL).
2.5. Antioxidant activity assays