Extraction, Purification, Structural Analysis And Antioxidant, Immunity Activities Preliminary Study Of Polysaccharides From Meretrix Meretrix Linnaeus

Meretrix meretrix Linnaeus, which mainly produced in the eastern coast of China, possess high nutritional and medicinal values. It has been used as food and traditional medicine for many centuries. Traditional medicine has proved extracts from Meretrix meretrix has effects on the treatments of inflammation, heat, sore and cancer. Modern research showed that polysaccharides of Meretrix meretrix Linnaeus had potent biological activities such as antioxidation, immunal-moluation, and anti-tumor activity. However, researches on the physicochemical property and biological activity polysaccharides from Meretrix meretrix Linnaeus are scarce. In this study, polysaccharides from Meretrix meretrix were extracted, purified, and structural elucidated, and antioxidant and immunomodulatory activities of purified polysaccharides were studied.The crude polysaccharide was obtained by enzymatic hydrolysis, ethanol precipitation, and removing of protein. The extraction yield of polysaccharides was between 6% and 10%. Four factors including enzyme type, enzyme amount, extraction time,and liquid ratio were optimized. The optimized extraction method was:trypsin content,2.0%; water ratio,1:10, extraction time,4 h. Protein in the extracted polysaccharides was removed 3 times by Sevage method. The polysaccharide fraction was further purified by DEAE-52 cellulose anion-exchange chromatography, and Superdex 200 dextran gel permeation chromatography. Two polysaccharide fractions were obtained, which named MMPX-1 and MMPX-2.Structures of polysaccharides MMPX-1 and MMPX-2 were characterized by UV, IR, NMR, GPC, periodate oxidation, Smith degradation, and methylation. The result showed that the average molecular mass of MMPX-1 and MMPX-2 were 1.04×106 Da and 5×105 Da, respectively. MMPX-1 was composed of mannose, glucose and galactose with the mole percent of 21.1%,29.9%, and 49.0%, respectively. MMPX-2 was composed of D-Glc and D-Gal with the mole percent of 87.7% and 12.3%. MMPX-1 had main chain of β-(1→4)-linked galactose, β-(1→4)-linked glucose, β-(1→4)-linked mannose, branch of α-(1→3)-linked glucose and teiminal glucose attached to C-6 site of β-(1→4)-linked galactose, along the main chain. MMPX-2 had main chain of α-(1→4)-linked glucose, branch of β-(1→3)-linked and teiminal galactoses attached to C-6 site of α-(1→4)-linked glucose.Polysaccharides MMPX-1 and MMPX-2 had antioxidant activities in vitro including DPPH scavenging, superoxide anion radicals scavenging, hydroxyl radicals scavenging, and total reduction capabilities. MMPX-2 had a better antioxidant effect than MMPX-1. Otherwise, polysaccharides MMPX-1 and MMPX-2 could stimulate macrophages to produce more NO, TNF-α, IL-6, IL-1β. MMPX-2 showed stronger immuno-regulating activity than MMPX-1.