Anticancer and chemopreventing natural products: some biochemical and therapeutic aspects.

Natural products have afforded a rich source of compounds that have found many applications in cancer chemotherapy. Furthermore, the vast structural spectrum of natural compounds can provide "lead compounds" for therapeutic improvement by molecular modification. Over 70% of anticancer compounds are either natural products, or natural product-derived substances. On the other hand conjugation of toxic natural products to monoclonal antibodies or polymeric carriers can lead to more efficacious targeted therapies. Since less than 15% of higher plants have been systematically investigated, the natural products research towards chemotherapy requires further attention and multi-scientific collaboration. An enforcing application to chemotherapy, using natural products, is also chemoprevention. Apart from vegetables and fruit, more than 1,000 different phytochemicals are already proved to possess interesting chemopreventing activities. Effectiveness of chemopreventing agents reflects their ability to counteract certain upstream signals that leads to genotoxic damage, redox imbalances and other forms of cellular stress. Chemoprevention by edible phytochemicals is now considered to be an inexpensive, readily applicable, acceptable and accessible approach to cancer control and management. The present short review deals with a number of recent biochemical and therapeutic routes, concerning current approaches towards natural anticancer agents in clinical practice, new candidate oncotherapy drugs from plants, marine and microorganisms, as well as promising chemopreventing agents from nature.