Study On Acetyl Salicylic Acid Modification And Antitumor Activity Of Fucoidans

Fucoidans is a kind of Marine sulphuric acid polysaccharide mainly extracted from brown algae.It not only has a wide source of raw materials,low toxicity,but also has anti-tumor,anti-virus,immune regulation and other physiological functions,which has attracted extensive attention of biological and medical researchers.However,the bioactivity of natural fucoidan is limited due to its high molecular weight,high viscosity and low absorbability.Structural modification is one of the effective methods to improve the activity and utilization of polysaccharides.However,there are few reports on the structural modification of fucoidan and the activity of its products.Therefore,in this paper,the acetyl salicylic acid derivative（ASA-CDI-DF）of fucoidan was synthesized by taking fucoidan as the research object and using acetyl salicylic acid（ASA）as the graft,and then its physical and chemical properties were analyzed,and the anti-tumor activity and mechanism of the modified fucoidan were preliminarily explored.The results obtained are as follows:1.Low molecular weight polysaccharide（DFSP）was prepared by H₂O₂-V_Ccombined oxidation method to degrade fucoidan（FPS）.The optimal oxidation degradation conditions were obtained by single factor test method:the concentration of H₂O₂and V_Cwas 25 m M,the ratio of material to liquid was 1:100（g/mL）,the degradation temperature was 50℃,and the degradation time was 2 h,the yield of DFSP prepared under this condition is 78.5%.2.The molecular weight of DFSP obtained based on the optimal oxidative degradation conditions was significantly reduced to 64.66 kDa,but its chemical composition was not significantly different from FPS,containing 21.40%sulfate group and 7.85%glucuronic acid,and its total sugar content was 71.17%,mainly composed of fucose and galactose.The results of FT-IR,XRD,Zeta-potential and particle size distribution showed that H₂O₂-V_Ccombined oxidation method did not destroy the basic structure of fucoidan,retained the active group-SO₄^2-,reduced the particle size of DFSP,and enhanced its dispersion in solution.3.Further,the acetylsalicylic acid derivative ASA-CDI-DF of fucoidan was synthesized by esterification of in situ activated acetylsalicylic acid（ASA）with DFPS as raw material.It was found that the amount of DFPS had a significant effect on the graft rate of acetyl salicylic acid.With the increase of the amount of DFPS,the graft rate of acetyl salicylic acid in ASA-CDI-DF increased first and then decreased.When the amount of DFPS was 1.2 g,the graft rate of acetyl salicylic acid was the highest,reaching 15.52%.The chemical composition of ASA-CDI-DF modified by acetylsalicylic acid showed that the content of sulfate group decreased,and the content of total sugar and uronic acid did not change significantly The results of molecular weight determination showed that after modification,the dispersion degree of fucoidan polysaccharides was significantly reduced,the molecular weight distribution was more uniform,and the homogeneity of polysaccharides was enhanced,which was conducive to the purification of ASA-CDI-DF and the play of biological activity.4.The antitumor activity and mechanism of ASA-CDI-DF were preliminarily investigated.Compared with FPS,ASA-CDI-DF treatment significantly inhibited the proliferation activity of A 549 cells,and showed obvious apoptosis phenomena such as nuclear fragmentation,chromatin condensation,decreased mitochondrial membrane potential（Δψ）and increased apoptosis rate.Further studies showed that ASA-CDI-DF inhibited the expression of p-NF-κB p65 protein in NF-κB pathway,and subsequently increased the expression of pro-apoptotic protein Bax,decreased the expression of anti-apoptotic protein Bcl-2,thereby activating the mitochondrial apoptosis pathway to induce tumor cell apoptosis.