Figure 5. Paeoniflorin (PF) protects ARPE-19 cells from H₂O₂-induced apoptosis via inhibition of caspase-3 activity. ARPE-19 cells were treated with 200 μM H₂O₂ or 200 μg/ml PF. Caspase-3 protease activity in ARPE-19 was determined as the release of p-NA from the substrate and was monitored colorimetrically at 405 nm. Quantitative analysis was performed by measuring the fluorescence intensity relative to the untreated cells. A negative control-induced sample was incubated with caspase-3 inhibitor (DEVD-CHO) before the addition of substrate. Each value represents the mean±SEM of three independent experiments (n=3 experiments, *p<0.05).