Determination of Total Phenolic Content. The total phenolic content (TPC) of the extract was estimated using a method by Wang et al.32 Briefly, 25 μL of gallic acid standard or purple tomato extract was mixed with 125 μL of FolinCiocalteu reagent in 96-well microplates and allowed to react for 10 min at room temperature. Then 125 μL of saturated sodium carbonate (Na2CO3) solution was added and allowed to stand for 30 min at room temperature before the absorbance of the reaction mixture was read at 765 nm using a visible-UV microplate kinetic reader (EL 340, Bio-Tek Instruments Inc., Winooski, VT, USA).32 The results were expressed in milligrams of gallic acid equivalent per gram of dry weight (mg GAE/g DW). All samples were tested in triplicate. Antioxidant Assays. Photochemiluminescence (PCL) Assay.