PGP and carcinoma: Recently many reports focus on the application of natural product such as flavonols or flavonoids, results demonstrated they had the decreased effect in the gene expression of multidrug resistance gene-1 (MDR1), and inhibit the transport activity and the of P-gp as well as the P-gp mediated drug efflux, consequently increase the intracellular concentration and cytotoxicity of chemotherapeutic agents, thus effectively reverse the resistance of MDR carcinoma cells in vitro (Liu et al., 2010; Lopez-Chavez et al., 2009).