Differences in responsivity of original cupric reducing antioxidant capacity and cupric-bathocuproine sulfonate assays to antioxidant compounds.

The cupric reducing antioxidant capacity (CUPRAC) method using bathocuproine sulfonate (BCS) as cuprous-chelating ligand claims to be an efficient substitute for the conventional CUPRAC assay using neocuproine; however, differences in their physical chemistry give rise to significantly varying responsivities to antioxidant compounds. The antioxidant capacity due to β-carotene (in acetone or dichloromethane) was fully measurable by conventional CUPRAC but not at all by cupric-BCS assay. Furthermore, CUPRAC exhibits distinctly stronger responses than cupric-BCS to naringenin, α-tocopherol, and bilirubin.