Protective effect of 3-O-methyl quercetin and kaempferol from Semecarpus anacardium against H2O2 induced cytotoxicity in lung and liver cells

Background: Hydrogen peroxide is continuously generated in living cells through metabolic pathways and serves as a source of reactive oxygen species. Beyond the threshold level, it damages cells and causes several human disorders, including cancer. Methods: Effect of isolated 3-O-methyl quercetin and kaempferol on H2O2 induced cytotoxicity, ROS formation, plasma membrane damage, loss of mitochondrial membrane potential, DNA damage was evaluated in normal liver and lung cells. The RT-PCR analysis used to determine Nrf 2 gene expression. Calorimetric ELISA was used to determine Nrf2 and p-38 levels. Expression of SOD and catalase was analyzed by Western blot analysis. Results: The present study isolated 3-O-methyl quercetin and kaempferol from the stem bark. They protected normal lung and liver cells from H2O2 induced cytotoxicity, ROS formation, membrane damage and DNA damage. Pre-treatment with 3-O-methyl quercetin and kaempferol caused translocation of Nrf2 from cytosol to nucleus. It also increased expression of p-p38, Nrf2, SOD and catalase in H2O2 treated lung and liver cells. Conclusion: The flavonoids isolated from S. anacardium significantly reduced H2O2 induced stress and increased expression of Nrf2, catalase and superoxide dismutase-2 indicating cytoprotective nature of 3-O-methylquercetin and kaempferol.