Butein is a plant polyphenol that acts as a specific protein tyrosine kinase inhibitor. Butein potently inhibits the tyrosine kinase activity of the EGF receptor (IC50 = 65 μM) and p60c-src (IC50 = 65 μM). The inhibition is competitive with respect to ATP and non-competitive with respect to the substrate. Butein is also a potent antioxidant and antiinflammatory agent which has been shown to inhibit glutathione reductase and rat liver GST (glutathione-S-transferase (IC50 = 9 μM)). Butein has been reported to activate sirtuins and promote the survival of eukaryotic cells. The Sirtuins, SIRT1-4 and SIRT7 are deacetylases relevant to histone modification. Butein directly inhibits IKK and suggested to also display inhibition towards PDE (c-AMP dependent PDE-IV). Also a potential CYP19 (Aromatase) inhibitor.