Polysaccharide refers to a class of structurally complicated and bulky carbohydrate synthesized from the condensation and dehydration of multiple single sugar molecules. It is one of the four fundamental substances that constitute life. Currently it has been extracted of polysaccharide from hundreds of species of plants and these plant polysaccharides have very important and special biological activity.

1, immunomodulatory effects
Studies have found that the most important pharmacological effect of plant polysaccharides is the immunomodulatory function. Plant polysaccharides having a broad spectrum of immune modulating activity and can play various kinds of physiological activity through the immunomodulatory effects. The regulation of plant polysaccharides on the immune system mainly include: activation of macrophages and natural killer cells to make them to produce associated cytokines; activation of B lymphocytes and T lymphocytes; activation of the complement system; affecting the body immune information; participating into the regulatory nerve - endocrine - immunity (NM) network; breaking the body immune tolerance caused by immune system damage as well as improving the recognition capability of the immune system to the antigen.

2, anti-tumor activity
The anti-tumor effect of plant polysaccharides is related to the way through which the glycoside bonds between monosaccharides are connected with each other. It is currently considered that the polysaccharides consisting mainly of β-D-glucan have significant anti-tumor activity. The anti-tumor activity of most kinds of polysaccharides is through activating the body's immune system to exert with a small number of polysaccharide instead of through the mediation of immune system, causing apoptosis, affecting signal transduction, membrane proteins and tumor cell adhesion and other factor for directly killing cancer cell. It features of anti-tumor activity is small or non-toxic side effects with appropriate combinations with chemotherapy drugs being capable of reducing or eliminating the adverse reactions such as bone marrow suppression caused by chemotherapy drugs.

3, anti-aging effects
The anti-aging effects of plant polysaccharides mainly exhibits in the following four aspects: strengthening the replication and synthesis of DNA, providing essential trace elements and nutrients to prolong animal growth, improving the animal resistance to non-specific stimulation to achieve stronger effect; regulating the metabolism of proteins, nucleic acids, carbohydrate and lipid; suppressing the lipid peroxidation and inhibiting the effect of lipofuscin; enhancing the superoxide dismutase (SOD) activity of body, scavenging the lipid peroxide (LPO) and malondialdehyde (MDA ) inside the body; inhibiting the effect MAOB for anti-aging.

4, hypoglycemic effect
The hypoglycemic effects of plant polysaccharides may be related to its impact of the activity of the enzyme participating into glucose metabolism, acceleration of the decomposition of sugar, inhibiting the hepatic gluconeogenesis or the output of muscle glycogen and promoting the glucose utilization of peripheral tissue as well as the hormone regulation. Study has found that the crude polysaccharides of portulaca oleracea is capable of significantly reducing the fasting blood glucose concentration, the concentration of serum total cholesterol and triglyceride concentrations as well as significantly raising the level of high-density lipoprotein and plasma insulin. Ganoderma lucidum polysaccharides have an obvious hypoglycemic effect on mice suffering from hyperglycemia caused by either alloxan or noradrenaline.

5, anti-inflammatory effect
The inflammatory effect refers to the defensive reaction of the vascular system of the living tissue against the damage factor; it is mainly manifested as redness, swelling, heat, pain and dysfunction, being the defensive reaction of the body towards the stimuli. Study has found that frondosa β- glucan has a significant anti-inflammatory effect in experimental animals with acute and chronic inflammation. Tremella aurantialba polysaccharide has inhibitory effect on rat allergic inflammation.

6, other kinds of effects
In addition to the biological activities mentioned above, plant polysaccharides also have various kinds of other effects such as anticoagulant activity, analgesic activity, anti-viral, anti-radiation, promoting the wound healing, reducing the liver damage and treatment of osteoporosis and other activity.

With the in-depth study of the biological activity of a variety of plant polysaccharides, plant polysaccharides have very broad prospects of development in the health food and pharmaceutical application. Polysaccharide has been becoming one of the important directions of today's drug development. In the future, we can predict that plant polysaccharides can surely make contribution to human health in various fields including anti-tumor, immunomodulatory and anti-oxidation.