Fig. (3) Isobolograms for green tea polyphenols and pharmaceuticals in the DPPH assay. The EC₅₀ values for a given pharmaceutical and GTE are placed on the graph, on X- and Y-axes, respectively. The isoboles of additivity are shown as dashed lines drawn between the appropriate EC₅₀ values. The solid points depict the experimental EC₅₀ values of the mixtures for their fixed-ratio combination.