Embelin (Embelic acid), isolated from the Japanese Ardisia herb, is an inhibitor of the X-linked inhibitor of apoptosis (IC50: 4.1 uM).

X linked:4.1 μM

Embelin from the Japanese Ardisia herb is a small-molecular inhibitor that binds to the XIAP BIR3 domain with which Smac and caspsase-9 bind. Embelin inhibits cell growth of both PC-3 and LNCap cells in a dose-dependent manner, with IC50 values of 3.7 and 5.7 μM. While, the toxicity of Embelin in normal PrEC and in WI-38 cells is much lower with IC50 values of 20.1 μM and 19.3 μM. Treatment of PC-3 cells with 25 and 50 μM of embelin for 48 h, 30% and 75% of cells undergo apoptosis, representing approximately 3-and 9-fold increase as compared to untreated cells. [1] Embelin also potently suppresses the biosynthesis of eicosanoids by selective inhibition of 5-lipoxygenase (5-LO) and Microsomal prostaglandin E2 synthase-1 (mPGES-1) with IC50 = 0.06 and 0.2 mM, respectively. [2]

Fluorescence Polarization Competitive Binding Assay: Fluorescence polarization experiments are performed in Dynex 96-well, black, round-bottom plates. A 5 μL sample of Embelin dilutions in DMSO, and preincubated XIAP BIR3 protein (0.06 μM) and the N terminus of a Smac peptide (SM7F) (0.01 μM) in the assay buffer are added to 96-well plates to produce a final volume of 125 μL. For each assay, the bound peptide control containing XIAP BIR3 protein and SM7F (equivalent to 0% inhibition) and free peptide control containing only free SM7F (equivalent to 100% inhibition) were included. The plates were mixed and incubated at room temperature for 3 h to reach equilibrium.

Cell growth is determined by the MTT-based assay using Cell Proliferation Reagent WST-1 according to the manufacturer's instruction. Cells (5000 cells/well) are grown in medium with 10% FBS, and various concentrations of Embelin are added to the cells. Four to five days later, WST-1 is added to each well and incubated for 1-3 h at 37 °C. Absorbance is measured with a plate reader at 450 nm with correction at 650 nm.(Only for Reference)