Researchon Isolation, Purification, Oxidative Degradation And In Vitro Activities Of Alginate

Alginate, also known as sodium alginate or sodium alginate, is a water-soluble acidic polysaccharide from brown algae cell wall, mainly obtained from seaweed, sargassum, kelp and other brown algae. It is a kind of natural biological macromolecules with a wide range of biological activity, widely used in medicine, food, chemical and other fields. Different polymerization degrees of alginate shows a variety of features. In this paper we choose kelp as raw material, because of its rich source and high contents of alginate. In order to improve its utilization rate and expand its application, we studied the ultrasonic assisted extraction process of alginate, purification, polymannuronate and poly guluronate fragment separation, degradation process, antioxidant activity and moisture absorption properties. The main results are as follows:1. Optimization of extraction process of Alginate polysaccharideBy using single factor test and orthogonal test without interaction, we optimized the technology of ultrasonic assisted extraction of alginate polysaccharide. The optimum conditions were as follows:low frequency ultrasonic,60(water/dry weight), 80 ℃, pH value of the solution 7, ultrasonic time 40min, extraction time 60min, ultrasonic power 350W. Through the range analysis and variance analysis, the influence sequence selected four factors on extraction rate were the ultrasonic frequency, the ratio of material to liquid, pH, extraction temperature value. The ultrasound frequency had a significant effect on the extraction rate. Under the same conditions, the ultrasonic assisted extraction rate compared with the traditional hot water extraction was increased by 67.25%.2. Purification of alginate polysaccharideAfter testing, we found alginate polysaccharide did not contain protein. So there was no need for protein removal. We obtained a polysaccharide fraction LJA after macroporous resin decolorization, dialysis and DEAE-23 cellulose column chromatography, Sephadex G-100 column chromatography. The water content of LJA was 12.62%. After completely dry, alginate content in LJA was 99.28% and uronic acid content was 98.65%. We found the polysaccharide was homogeneity after cellulose acetate film electrophoresis and HPLC.3. Preparation of alginate oligosaccharideAccording to the different physical and chemical properties between polyM and polyG, we could achieve separation of their. Finally, we could acquire the elaboration products of PM and PG. The molecular weight of PM was 6204. The molecular weight ofPG was 6138.In order to obtain the oligosaccharide with average molecular weight of about 1500, we respectively studied the optimal conditions for the preparation of hydrogen peroxide degradation. The optimal degradation conditions LJA were 5%alginate solution, pH5.0,3% H2O2,90℃ water bath, stirring reaction 2h. The optimal degradation conditions PM and PG were 5% alginate solution, pH5.0,2% H2O2,90℃ water bath, stirring reaction 2h. Through FTRI analysis, the oligosaccharides still maintained the original structure, only some oligosaccharides’aldehyde group at the C1 was oxidized to carboxyl group.4. The antioxidant activity and the moisture absorption and moisture retention activity of alginate and its oligosaccharides in vitroAlginate and its oligosaccharides had a certain inhibitory effect on hydroxyl radical, superoxide anion and lipid peroxidation in vitro. In the experimental concentration range, their activity were in a concentration dependent manner. And the smaller molecular weight showed higher inhibitory activity. OM on the hydroxyl radical scavenging activity was the highest, but OG on superoxide anion scavenging activity was the highest and had good ability of lipid peroxidation.Alginate and its oligosaccharides showed a stable moisture absorption ability in different relative humidity environments (43%,81%), also had a good moisturizing effect in the dry environment of silica gel. LJA in the series of polymerization degree of alginate not only has the highest moisture absorption performance, but also has the best moisturizing effect.