Antioxidant compounds tested by EHRA (R2 = 0.92, closed symbols) and DPPH assay (R2 = 0.65, open symbols). Each point represents the IC50 value obtained from the serial dilution of an antioxidant compound (errors bars ±SD, n = 3). Symbols represent 1 cysteine (square), 2 α-tocopherol (circle), 3 ferulic acid (diamond), 4 ascorbic acid (upward triangle), 5 gallic acid (downward triangle), 6 quercetin (right triangle)