HepG2 cells were plated in six well plates (7 × 10⁵cells/well/3 ml of medium) and incubated at 37°C overnight. Ethacrynic acid and quercetin were then added to wells at various concentrations for 1 h. After incubation with the inhibitors, cells were collected by trypsinization and homogenized by ultrasonication. The homogenate was centrifuged at 10,000 gfor 20 min and the supernatants were used for GST activity analysis as described under Materials and Methods. GST activity was expressed as nanomoles of dinitrophenylglutathione formed per minute per milligram of cellular protein at 37°C.