Advances in dietary polysaccharides as anticancer agents: Structure-activity relationship

The discovery of nutritious dietary supplements and side effect-free therapeutics are a priority in the current scenario of increasing cancer cases. Natural anticancer polysaccharides have shown immense potential. As a class of biomacromolecules produced by a variety of species including plants, animals, fungi, bacteria and algae, polysaccharides have drawn considerable interest over the recent years as they possess anticancer activities with fewer side effects. Natural polysaccharides from different sources have various structures and anticancer activities. But it is difficult to compare their bioactivities with those of synthetic drugs for their inherently physicochemical properties, including poor water solubility, low molecular weight and branching degree. However, some chemical modification methodologies (e.g., sulfation, phosphorylation, selenylation and zinc impregnation) could significantly increase the water solubility, molecular weight by grafting other groups to boost their anticancer activity. Numerous studies have focused on the evaluation of anticancer mechanism of action for polysaccharides from different sources and further applications. Polysaccharides are considered as anti-tumor agents for their immunomodulatory activity and low toxicity and side effects. Numerous polysaccharides have been used for clinical or adjuvant treatment of tumors. However, the complex structure of some polysaccharides and their unclear anti-cancer mechanism of action brought great restrictions on their research and further clinical application. Therefore, it is important for human to resist tumors by elucidating the antitumor effects of polysaccharides from different resources and their correlation, discussing the application of anticancer polysaccharides in combination with chemotherapy drugs and anticancer vaccine adjuvants.