| Mannose-oligosaccharides (MOS) is a kind of functional oligosaccharides. The beneficial actions of oligosaccharides are assumed as following: inhibit growth of pathogenic and/or harmful bacteria, stimulate the immune functions, reduce level of cholesterol and risk of cancer, improve digestion and/or absorption of food ingredients/minerals and vitamins. Oligosaccharides are usually synthesized by enzymatic method, which not only suffers from the problems of time consuming and low yields but also may result in the pollution of environments. The current chemical syntheses of oligosaccharides are also limited by high costs and bothering purification steps. Just on the spot, microwave-assisted solid-phase synthesis of oligosaccharides offers us an ideal resolution with the advantages of rapidity, high yields and without environmental pollutions. In the present work, we optimized the reaction conditions for microwave-assisted solid-phase synthesis of MOS. And the effects of MOS on the scavenging rate to free radicals, the antioxidation and the immunity in rats were investigated in this thesis.First and foremost, the reaction conditions were optimized by single factor experiment and orthogonal test. The results show that the optimized condition for microwave-assisted solid-phase synthesis of MOS as follows: 1000 w of microwave power,4 min of microwave irradiation time, 15% water as initiator, 3% acid A as the catalyst, with a yield of 86.50%. The as-prepared oligosaccharides were analyzed by HPLC using a Sugarpack-1 column at 85℃. The results suggest that the main constituents of the as-prepared oligosaccharides are as follows: 13.50% monosaccharide, 3.82% disaccharides, 7.56% trisaccharides, 6.84% tetrasaccharides, 4.77% pentasaccharides, 5.54% hexasaccharides, and 57.97% oligosaccharides with higher molecule weight.The results indicate that MOS could efficiently scavenge the hydroxyl radical in vitro with the IC50 of 4mg/mL. Meanwhile, the scavenging rate to hydroxy radical, the activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in plasma, liver, small intestine and pancreas of rats administrated by MOS were significantly higher than those of all control, glucose and mannose treated rats. Likewise, the level of glutathione (GSH) and total anti-oxidative ability (T-AOC) significantly increased (p<0.05), with the level of malondialdehyde (MDA) and reactive oxygen species (ROS) significantly decreased (p<0.05). In conclusion, MOS synthesized with microwave irradiation play a positive role in anti-oxidation in rats by raise the scavenging rate to free radicals and the activity of antioxidant enzymes.The experiment was also designed to investigate the effect of MOS on immune system of rats. The results show that the weight of thymus increased (p>0.05) compared to the control, and the weight of spleen, serum IgG,IgA and IgM are significantly higher than those of all control, glucose and mannose treated rats. And all rats treated with MOS show significant increase on the stimulation index (SI) (with/without ConA) of thymus and spleen. It is therefore believed that the microwave-assisted solid-phase synthesized MOS can promote the level in cell mediated immunity and humoral immunity.
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