Figure 5.

Oxidative stress. HT 29 cells were seeded in 6-well flat bottom plates at 1 × 10⁶ viable cells/mL. The cells were treated with the following concentrations of cytotoxic agent for 24 h (DCF test) or 48 h (SOD and catalase activity): control = culture medium without Uncaria tomentosa extract or oxaliplatin; chemotherapy = oxaliplatin 20 μmol/L; Uncaria = Uncaria tomentosa extract 750 μg/mL; Uncaria + chem. = Uncaria tomentosa extract 750 μg/mL + oxaliplatin 20 μmol/L. The cells were collected and adjusted to a concentration of 1 × 10⁶ cells/mL in PBS buffer. (a) SOD activity: the units of SOD are defined by the amount of enzyme that inhibits 50% of adrenaline oxidation and were expressed as units per 10⁶ cells. (b) Catalase activity was calculated using the molar extinction coefficient (0.046 mM⁻¹ cm⁻¹), and the results were expressed as picomoles of catalase per 10⁶ cells. (c) ROS production was estimated using the probe DCFH-DA, which is oxidized to fluorescent DCF. Different lowercase letters represent statistically significant differences among the treatments (P < 0.05).