Dissolution Kinetic Models Of Polysaccharides From Porphyra Yezoensis And Their Stimulated Digestion In Vitro And Biological Activitity Research

Polysaccharides isolated from Porphyra yezoensis are often purified and then applied as health care products for its significant biological function of antilipemic,anti-tumor,antioxidation,anti-aging,enhancing body immunity.However,as a kind of daily food,the polysaccharide dissolution in Porphyra yezoensis soup,as well as the digestion in human physiological condition and the biological activity of the polysaccharide digesta has not been reported yet.In this paper,Porphyra yezoensis was used to investigate polysaccharide dissolution kinetic models.And the saliva,gastric and intestinal digestion of crude polysaccharides(PS)from Porphyra yezoensis by water extraction and ethanol precipitation were simulated and analyzed.Antioxidant and anti-tumor activities of the polysaccharides before and after in vitro digestion were also studied.Main research conclusions are summarized as follows:(1)The diffusion kinetic models established based on Fick's second law for polysaccharides from Porphyra yezoensis of both spherical and slab geometries were investigated in this paper.The polysaccharide concentrations in the Porphyra yezoensis soup were measured at different immersing temperature and different time.Results showed that the dissolution of polysaccharides from Porphyra yezoensis in the spherical model was significantly higher than that in the slab one.Statistical results suggested that the kinetic model calculation values coincide well with the experimental data(R>0.933).And a series of kinetic parameters were gained.The apparent kinetic constants and diffusion coefficients both increased with temperature.The apparent activation energy were 5.984 kJ/mol and 1.406 kJ/mol in the spherical and slab models,respectively.The relative yield of the polysaccharide dissolution was in accordance with exponential models.The kinetic models established the theoretical foundation for the optional immersing process for Porphyra yezoensis polysaccharides.(2)Crude polysaccharides(PS)from Porphyra yezoensis by water extraction and ethanol precipitation and their physicochemical properties were determined.Polysaccharide content and protein content of PS were 71.15% and 0.42%,respectively.In fourier-transform infrared(FT-IR)spectrum showed PS were composed of pyranoses and sulfate group.Monosaccharide composition analysis showed PS were composed of xylose,mannose,glucose and galactose.High gel chromatography results showed that the PS had a wide range of molecular weight(Mw)distribution,its Mw was among 5.3×106 ~1.3×105 Da.(3)The saliva,gastric and intestinal digestion of PS were investigated in vitro.Results showed that salivary amylase had no effect on PS;however,the PS was influenced in later gastrointestinal digestion.Steady decreases in Mw of the PS from158.71 ± 1.54 to 19.1 ± 0.68 kDa and from 19.1 ± 0.68 kDa to 18.57 ± 0.03 kDa respectively,were observed during the gastric digestion and intestinal digestion.Meanwhile,the reducing ends increased from 20.1 ± 0.1 to 34.1± 0.2 mg/g and from34.1± 0.2 mg/g to 36.1 ± 0.2 mg/g;in addition,there was no monosaccharide released throughout the whole digestion period,indicating the decrease of Mw may due to the breakdown of glycosidic bonds.A maximum decrease in Mw of the PS was also found within the first one hour during the gastric digestion,suggesting that lower molecular weight might mainly due to the effect of acid pH of gastric juice.(4)The antioxidative activities of PS before and after in vitro digestion were investigated using various assays in vitro,including scavenging abilities on DPPH,superoxide and hydroxyl radicals and reducing power.Results showed that the PS and its digesta after oro-gastro-intestinal digestion in vitro could well eliminate superoxide anion(EC50 value 2.64 and 1.81 mg/mL),hydroxyl radicals(EC50 value 5.24 and 4.48mg/mL)and DPPH·free radicals(EC50 value 10.05 and 7.34 mg/mL),and their reducing power ability in dose-dependent manners.Results implied that in vitro digestion lead to better antioxidant activity of polysaccharides.In addition,results of the antitumor assays in vitro showed that PS and its digesta after oro-gastro-intestinal digestion in vitro presented notable inhibition effect on HepG2(IC50 value 2688 and1813 ?g/mL),SGC-7901(IC50 value 1825 and 1505 ?g/mL),and SW-480(IC50 value2549 and 1917 ?g/mL)in dose-dependent manners obviously.Simulated digestion could contribute to the cancer cell proliferation inhibition of PS on these three cancer cells in different degrees.This could be of significance to the inhibition effect on the proliferation of tumor cells,and lay the foundation for research on mechanisms of invivo antitumor activity.