Effect of guaraná on Trp destruction in CuSO
-induced LDL oxidation. LDL (50 μg protein/mL) was incubated in PBS with 5 μM CuSO4 with different guaraná concentrations. Fluorescence (Ex/Em = 282/331 nm) was measured at intervals of 20 min at 37°C. The t(1/2) means the time required for reaching half Trp fluorescence. Experiments were repeated three times, showing similar results. * p < 0.05 compared to control with copper and without guaraná (black bar).