ABSTRACT
Plants have been used throughout history as an indispensable source of natural products for medicine. This chapter presents the components of plant primary and secondary metabolism, with an emphasis on plant-derived compounds with antitumor properties, their chemical structure, properties, isolation, and mode of action, among other information. Primary metabolism is the total of processes leading to the production of the four major classes of compounds accounting for about 90% of the biological matter and that are, in consequence, required for the growth of plant cells. These are sugars, amino acids, lipids, and nucleotides. Secondary metabolites are compounds belonging to extremely diverse chemical groups, such as organic acids, aromatic compounds, terpenoids, steroids, flavonoids, alkaloids and carbonyls. In spite of the plethora of plant metabolites with tumor cytotoxic or immuno-stimulating properties, plants may not be an ideal source of natural anticancer drugs. Flavonoids are cytotoxic against cancer cells, mostly in vitro.
