Effects of guaraná on LDL oxidation. LDL (50 μg protein/mL) was incubated in PBS 10 mM (pH 7.4) at 37°C in the presence of CuSO4 5 μM. Conjugated diene formation was measured by determining the absorbance at 234 nm every 20 min. In panel A, incubation medium did not contain guaraná (1) or contained 0.05 μg/mL (2), 0.1 μg/mL (3), 0.5 μg/mL (4), 1 μg/mL (5) or 5 μg/mL (6) of guaraná and control without CuSO4 and guaraná (C). In panel B, the value of the lag phase determined graphically by the intercept of the tangents to the slow and fast increase of the diene absorption. Experiments were repeated six times, showing similar results. * p < 0.05 compared to group without CuSO4 and guaraná. † p < 0.05 compared to group with CuSO4 and without guaraná.