Dose response curves of inhibitory activities of MG132, baicalein, pectolinarin, myricetin, hispidulin, isoliquiritigenin and quercetin. The IC50 values were calculated by fitting with the four parameter logistic (4-PL) model: A. MG132 IC50=27.97 μM, R2=0.99. B. baicalein IC50=45.65 μM, R2=0.97. C. pectolinarin IC50=49.96 μM, R2=0.97. D. myricetin IC50=55.39 μM, R2=0.96. E. hispidulin IC50=58.31 μM, R2=0.97. F. isoliquiritigenin IC50=63.90 μM, R2=0.99. G. quercetin IC50=71.29 μM, R2=0.96. R2, adjust R square values. Dose response curves of inhibitory activity were presented. Data are shown as mean ± SD of three independent experiments.