Microwave Assisted Solid-state Oligosaccharides Synthesis And Its Effect On Antioxidation And Immunity Activity In Mice

Microwave-assisted solid-state synthesis of oligosaccharides offers us an ideal resolution with the advantages of rapidity, high yield and less environmental pollution. In the present work, we optimized the reaction conditions of microwave-assisted solid-phase synthesis of oligosaccharides (glucooligosaccharides (GOS) and mannooligosaccharides (MOS)). And the effects of MOS on the scavenging rate of free radicals, the antioxidant enzymes and immunity activities in mice were investigated.Optimal experiment show that the optimal condition of microwave-assisted solid-phase synthesis of GOS as follows: 1000 w of microwave power, 9 min of microwave irradiation time, 30% water as initiator, 4% phosphoric acid as the catalyst. The yield of product was 76.56%. The product was characterized by HPLC. The components of synthetic product was determined as follows: 20.81% disaccharides, 15.50% trisaccharides, 10.84% tetrsaccharides, 7.79% pentsaccharides, 21.63% oligosaccharides with higher molecule weight beyond hexsaccharides. The optimal condition of 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% phosphoric acid as the catalyst. The yield of product was 86.50%. The product was characterized by HPLC. The components of synthetic product was determined as follows: 13.50% mannosaccharides, 3.82% disaccharides, 7.56% trisaccharides, 6.84% tetrsaccharides, 4.77% pentsaccharides, 5.54% hexsaccharides, 86.50% with higher molecule weight beyond heptasaccharide.The results indicate that MOS could efficiently scavenge the hydroxyl radical in vitro with the IC50 of 4mg/ml. The animal experiment show that high-fat diet or d-gal administration can significantly increased oxidative stress (P<0.05) in untreated model mice compared to the normal control mice. The MOS diet administration can significantly enhance the level of glutathione (GSH), the activities of superoxide dismutase (SOD), catalase (CAT), Na+-K+-ATP and glutathione peroxidase (GSH-Px) and reduce NO- and MDA levels (P<0.05) in plasma, liver, small intestine, large intestine, stomach and pancreas of high-fat mice compared to those of the untrated model control mice (P<0.05).The experiment was also designed to investigate the effect of MOS on immune activities of mice. The results show that some immune indexs in aged mice were significantly decreased (P>0.05) compared to the young control. The MOS diet administration can significantly increased the weight of thymus, spleen, liver and kidney and the levels of serum lgG, LgA and lgM (P<0.05). Moreover, all mice feeded with MOS diet show a significant increase in the stimulation index (SI) (with/without ConA) of thymus and spleen (P<0.05). It is therefore believed that the MOS diet can enhance the activity of antioxidant enzymes and improve immunity activity in mice.