Butein (2’,3,4,4’-tetrahydroxy Chalcone), a plant polyphenol, is isolated from Rhus verniciflua. It can inhibit the activation of protein tyrosine kinase, NF-κB and STAT3, and also can inhibit EGFR.

Butein inhibits the epidermal growth factor (EGF)-stimulated auto-phosphotyrosine level of EGF receptor in HepG2 cells, and also inhibits tyrosine-specific protein kinase activities of EGF receptor and p60c-src with IC50 of 65 μM in vitro. The inhibition is competitive to ATP and non-competitive to the phosphate acceptor, poly (Glu, Ala, Tyr) 6:3:1 for EGF receptor tyrosine kinase. In contrast, Butein non-significantly inhibits the activities of serine- and threonine-specific protein kinases such as PKC or PKA. [1] Butein inhibits Nuclear Factor(NF)-κB and NF-κB-regulated gene expression through direct inhibition of IκBα Kinase β on Cysteine 179 Residue. [2] Butein (10 μM) inhibits over 90% iNOS and COX-2 expression, as well as nitrite and TNF-α production in LPS-stimulated RAW 264.7 cells. Butein (10 μM) inhibits LPS-induced DNA binding activity of NF-κB, which is mediated through inhibition of the degradation of inhibitory factor-κB and phosphorylation of Erk1/2 MAP kinase, as well as increases binding of the osteopontin a vb3 integrin receptor. [3] Butein (20 μM) treatment induces morphologic changes of bladder cancer cells BLS(M) from elongated morphology to rounded epithelial-like cells, accompanied by downregulation of vimentin, and gaining of E-cadherin compared to untreated control cells, indicating the reversal of mesenchymal-like phenotype. Butein (20 μM) suppresses motility and invasion capacity of BLS(M) cells, and reverts EMT-like phenotype induced by TNF-α, through the ERK1/2 and NF-κB signaling pathways. [4]

Butein at 2 mg/kg induces significant inhibition of hepatocellular tumor growth compared with the corn oil-treated controls. At necropsy on day 22 after initial treatment, there is more than 2-fold decrease in tumor growth in the Butein-treated group (mean relativetumor burden, 3.90) compared with the control group (8.46), associated with reduced constitutive p-STAT3 (9% vs 81% of vehicle group), Bcl-2 levels (26% vs 96% of vehicle group), and increased caspase-3 level (98% vs 21% of vehicle group) in HCC tumor tissues. [5] Butein shows antifibrogenic activity. Butein (25 mg/kg/day) reduces serum AST and ALT activation to 35% and 69%, respectively, of control CCl4-induced rat levels. Butein (25 mg/kg/day) reduces liver hydroxyproline contents and TBAR4 concentration to 54% and 54%, respectively. α1(I) collagen and TIMP-1 expression in Butein-treated rats is 28% and 20.3% compared with the values for the respective CCl4-treated control. [7]

The cells (5× 103/mL) are incubated in triplicate in a 96-well plate in the presence or absence of indicated concentration of Butein in a final volume of 0.2 mL for different time intervals at 37 ℃. Thereafter, 20 μL MTT solution (5 mg/mL in PBS) is added to each well. After a 2-hour incubation at 37 ℃, 0.1 mL lysis buffer (20% SDS, 50% dimethylformamide) is added, incubation is continued overnight at 37 ℃, and then the optical density at 570 nm is measured by plate reader. (Only for Reference)