Figure 3.

Immune checkpoint blocking effects of isolated compounds by competitive Enzyme-Linked Immunosorbent Assay (ELISA). Effect of PD-L1 inhibitor C1, compounds eriodictyol (7) and fisetin on PD-1/PD-L1 binding activity (9) (A); effect of anti-CTLA-4 antibody (Ipilimumab), compounds protocatechuic acid (2) and caffeic acid (19) on CTLA-4/CD80 binding activity (B). The relative binding activity was normalized to the relative percentage of the vehicle control group. Half-maximal inhibitory concentration (IC₅₀) was calculated using Prism “log[inhibitor] vs. normalized response” equation. All results are presented as the mean of three independent biological replicates. * p < 0.05, ** p < 0.01, *** p < 0.001, compared with the vehicle control group.