| Tea polysaccharides(TPS) is a kind of acid polysaccharides combined with proteins or an acid glycoprotein, and the polysaccharides compound have bioactivity. Scavenging free radicals function of tea polysaccharides was already reported. Study on chemical modification of tea polysaccharides and scavenging free radicals activity before and after modification could preliminarily explore chemical modification conditions and influence of the biological activity of tea polysaccharides, which could provide reference for the development and utilization of tea polysaccharides. Tea polysaccharides was extracted from green tea and acetylation, sulfation, and carboxymethylation modification were separately selected to study on scavenging free radicals activity in vitro of purified tea polysaccharides in the experiment. The results showed that:1. Influence of three experimental factors on substitution degree of green tea polysaccharides of acetylation modification were: mass of tea polysaccharide/ volume of acetic anhydride> holding time > reaction temperature, the optimal conditions of acetylation modification were: mass of tea polysaccharide/ volume of acetic anhydride 1:40, holding time 4 h, reaction temperature 30 ℃. The results showed that superoxide anion free radical, hydroxyl free radical and NO2- scavenging effects were improved in different level after acetylated modification, and the increase of NO2- scavenging effects was most pronounced.2. Effect of three experimental factors on substitution degree of sulfation modification were: volume of pyridine/volume of chlorsulfonic acid > reaction temperature > reaction time, the optimal conditions of sulfation modification were: volume of pyridine/volume of chlorsulfonic acid 4:1, reaction temperature 60 ℃,holding time 4 h. Superoxide anion free radical, hydroxyl free radical and NO2- scavenging effects were improved after sulfated modification, and differences of scavenging effect between before and after sulfated modification was significant.3. Influence of three experimental factors on substitution degree of carboxymethylation modification were: mass of Na OH / mass of monochloroacetic acid > reaction temperature > holding time, the optimal conditions of carboxymethylation modification were: mass of Na OH /mass of monochloroacetic acid 1:2, reaction temperature 55℃, reaction time 5h. Superoxide anion scavenging effects were improved after carboxymethylation modification.4. The results showed that scavenging activities of superoxide anion free radical, hydroxyl radical and NO2- were increased with the increase of acetylation, sulfation, and carboxymethylation modification substitution degree. |
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