Natural products: promising resources for cancer drug discovery.

Natural products are important sources of anti-cancer lead molecules. Many successful anti-cancer drugs are natural products or their analogues. Many more are under clinical trials. The present review focuses on chemopreventive and anti-cancer activities of polar and non-polar extracts, semi purified fractions and pure molecules from terrestrial plants of India reported between 2005 and 2010 emphasizing possible mechanisms of action of pure molecules.