Quantification of Total Phenols by UV-Vis

TP quantification was performed by UV-visible spectrophotometry according to [57 (link)]. A volume of 1 mL of diluted extract was placed in a 15 mL test tube; 6 mL of distilled water and 1 mL of Folin–Ciocalteu reagent were added, and the mixture was left to rest for 3 min. Subsequently, 2 mL of 20% Na₂CO₃ (w/v) was added and heated at 40 °C for 2 min. This reaction formed a blue chromophore; its absorbance was measured at 760 nm on a Shimadzu UV-VIS model 2600 spectrophotometer (Shimadzu, Kyoto, Japan). Five extraction cycles were needed to get 100% TP recovery. Results were expressed as milligrams of gallic acid equivalents (GAE) per gram of dry weight (mg GAE g⁻¹ DW).