Inhibition of IKKβ phosphorylation activity. Microtiter plates with GST-IκBα were incubated with IKKβ together with 1 at the indicated concentrations. GST-IκBα phosphorylated level was detected using an anti-phospho IκBα (Ser32/Ser36) antibody and horseradish peroxidase conjugated secondary antibody. Approximate IC50 value of 1 = 50 μM. Error bars represent the standard deviations of the results from three independent experiments.