| Seaweed polysaccharides are important natural products from algae, widely used in food industry and medicine for years. The size or degree of polymerization of polysaccharide plays a critical role in determining their applications. Polysaccharides with large size tend to be insoluble or highly viscous in solution, to which may have limited their applications. A decrease in molecular weight can substantially enhance their utility. Now they are showing increasingly great value for the deeper research and development of physiological and bioactive compounds. For example, some oligosaccharides produced by chemical or enzymatic degradation of seaweed polysaccharides showed some interesting is biological activities, such as anti-inflammation, anti-tumor and antioxidant activities. It is critical to understand the precise roles they play in biological processes and elucidate the structure-bioactivity relationship for the deeper development of new medicine. Agar is a gelatinous polysaccharide extracted from certain species of the 20 Rhodophyceae, the predominant structure was found to be a linear. altertiating DL-galactan comprising of 13-(1 -4)- linked units of 3,6-anhydro-a-D- galactopyranosyl-(1- 3)- D-galactopyranose . This sequence was defined as ~agarose?and comprises approximately 70% of the agar polysaccharide .The remainder is agarose substituted with sulphate half-ester , methyl ether and 25 pyruvic acid ketal. In our study, we used agar as the starting material and tried several degradation method to find a suitable method to prepare agaro- oligosaccharides. such as acid hydrolysis catalyzed by dilute hydrochloric acid, 11,0, and CH3COOH, and oxidative-reductive depolymerization (ORD) via OH*, using enton?type reagents (hydrogen peroxide in conjunction with ferrous ions) as sources. The reaction processes of ORD and the acid hydrolysis by HCI have been monitored by viscosity measurement. The initial results indicated that the accelerated degradation of agar by Fenton type reagents to mimic naturally 5 occuring ORD reaction has several advantages over methods like acid hydrolysis particularly in questions regarding the characteristic composition of agar, 3,6-AG and the degradation rate aspect. The low molecular weight agars (LMWA). produced by *OH using the ascorbate induced Fenton type reagents as sources, have been characterized by IR spectra, ?C NMR, Negative MALDI-TOF-MS and 10 biological activities evaluation. The results of these instrumental analyses showed that the ORD is more representative but less specific than acid hydrolysis. In order to investigate the structure-activity relationship of the degradation products, we have prepared by size exclusion chromatography agar fractions of different niolecular masses. Our experiments showed that the inhibitory activities of IS ulucosidase are dependent on the niolecular weight of the products. The reduction in molecular weight significantly enhanced the inhibitory capacity of the degradation products. In addition, according to the principle of MTT method, we designed to form *OH by UVa and UVb radiating the fibroblast of human derma, and then evaluated the radical scavenging activity of the degradation products 20 through the protective action of these injury fibroblast. The results showed...
|
PDF Full Text Request