Isolation, characterization, and biological activities of polysaccharides from medicinal plants and mushrooms

Polysaccharides from medicinal plants and mushrooms form a major class of bioactive compounds with a wide range of pharmacological activities. Some of their biological activities include antioxidant, immunomodulatory, antitumor, gastrointestinal protection, antidiabetic, and hepatoprotective effects. Immunomodulatory and antitumor activities of polysaccharides, from medicinal plants and mushrooms, are of special interest in this review. The epidermal growth factor receptor molecules, such as HER family receptors, play a critical role in the formation and growth of cancer. Rational development of targeted therapeutic agents requires a clear understanding of cancer at the molecular level. This chapter therefore attempts to provide a molecular basis of cancer formation, development, and growth. This chapter then provides strategies for rational screening programs for the discovery of targeted cancer therapeutics. Major part of the plant-based polysaccharide research in biomedical arena has so far been on crude extracts or partially purified polysaccharides. To understand the precise function of plant/mushroom polysaccharides in immunomodulatory and antitumor mechanism, there is an urgent need for the development of improved separation and purification techniques that will allow a study of detailed structure-function relationship. A review of literature on separation methods is provided in this chapter, which is followed by suggestion for novel strategies for the purification of polysaccharides extracted from plant/mushroom sources. Methods for structural characterization of bioactive polysaccharides will then be highlighted after a brief discussion on structure-activity relationship. The mechanism of action of plant polysaccharides as anticancer agents is then briefly discussed. Finally, this chapter provides possible directions for future research in this important area.