In vitro kinase assays with piceatannol and BTB14431. Inhibition of CSN-associated kinases by curcumin- and emodin-derived compounds in vitro. A, Piceatannol, identified by searching the database with curcumin as a lead compound and B, BTB14431, a compound found by searching the database with emodin. Recombinant CK2 and PKD as well as purified CSN were used to phosphorylate c-Jun in vitro. The first lane (0) is without inhibitors. Piceatannol (A) and BTB14431 (B) were added in increasing concentrations (20, 50, 100 and 200 μM). The shown autoradiographs were evaluated by densitometry. The obtained data were plotted against increasing inhibitor concentrations and used to calculate IC50 values summarized in Table 2. The demonstrated results are representative for at least four independent experiments.