ABSTRACT
Cancer, the leading cause of death worldwide, occurs when the old and damaged cells, instead of undergoing apoptosis or programmed cell death, ignore the death signals and convert into less-specialized tumor cells and undergo unregulated cell proliferation. For cancer chemotherapy natural products have been the first choice of drugs for over the last 50 years. These natural products are generally secondary metabolites, having small molecular size and being obtained from plants, microorganisms and marine organisms. This is because natural products exhibit the necessary structural diversity, steric complexity and conformation which makes them biologically active and imparts drug-like properties in them. It is also seen that nearly 47% of the commercially available anti-cancer drugs in American, European and Japanese markets are of natural origin or semi-synthetic. Earlier such biologically active molecules were obtained through bioassay-guided isolation method. But, extraction and isolation of active molecules from crude extracts following such traditional procedures is laborious, time-taking and expensive. Therefore, a considerable decline in the discovery of newer anti-cancer drugs in the market was also seen almost 20 years back. With the advent of high-throughput screening technologies selection of active molecules have become easier. These techniques have eased the screening and streamlining of untapped natural product resources. Development of recent advanced technologies has helped in getting better insights into the different cancer pathways. Coupling of these newer technologies with the traditional methods has marked the dawn of newer onco-therapeutic agents, many of which are now in preclinical and clinical stages. This chapter discusses the various anticancer activity possessing biologically active molecules which have reached preclinical and clinical stages.
