| Fucoidan is a characteristic water-soluble heteroglycan, existing in brown alga,which contains sulfates and excellent biological activity. But there were manydifferences of chemical composition, structure and biological activity betweenfucoidan with different molecular weights. The digestion and oral absorption of highmolecular weight fucoidan were questioned.Therefore, knowledge of the absorptivecharacteristics and activity of fucoidans after oral administration is very important inthe develorment of fucoidan functional products and the view of promoting the wholelevel of fucoidan processing industry. On this background, crude fucoidan was chosenas material, and the chemical composition and activity were employed as the subjectof this research. The main researches in this thesis are listed below:1. Chemical composition of fucoidan fractions under different preparationconditions: Different fucoidan fractions were obtained by anion-exchangechromatography on Q-Sepharose FF and free radical oxygen degradation andultrafiltration technology from high molecular weight fucoidan extracted from S.japonica. The weight-average molecular weight and chemical composition ofdifferent molecular weight fucoidan fractions were compared.The F-1(26kDa) andF-2（34kDa）can be eluted by1mol/LNaCl and2.5mol/LNaCl with sulfated estercontent of13.44%and29.57%respectively.The optimum degradation condition toyield highly sulfated low molecular weight fucoidan was4.5%H2O2and0.0267mol/LCu2+from4.5g crude fucoidan. Two highly sulfated fractions Fa3（Mw7.68kDa）andFb3（Mw3.89kDa）were obtained with the sulfated ester content of30.32%and32.48%respectively. Low molecular weight fraction Fa3was mainly made up offucose (64.25%) and galactose (30.74%), while the fucose content of fraction Fb3decreased to46.94%, though it had a higher content of sulfated ester. 2. The determination for fucose content from rat serum. A high performanceliquid chromatography with precolumn derivatization (PMP-HPLC) has beendeveloped for the determination of the levels of fucose in rat serum accurately. ThePMP-HPLC method was more sensitive, accurate, reproducible and suitable to meetthe qualitative and quantitative detection of fucose content in serum. At the same time,other five kinds of monosaccharides(mannose, galactosamine, glucosamine, glucoseand galactose)can be detected quantitatively.The fucose recovery was from102.7%to105.3%and RSD was1.31%.3. Oral absorption and bioavailability of fucoidan with different molecularweights in rats. We characterize the absorptive course of fucoidan and degrationproducts in rats by PMP-HPLC. The absorption rate of fractions with mediummolecular weight absorption is relatively slow, the trend of serum fucose is notobvious, while the low molecular weight components by the free radical degradationgreatly increased.The results showed that fucoidan with a medium molecular weightand charge density could be absorbed and the polymer cross the gut wall at a ratevarying inversely with polymer size.4. The immune function of different fucoidan fractions was studied. Mice weredivided into twelve groups and given different molecular fucoidan fractions.Theresults showed that both of the the low and medium molecular weight fucoidan couldantagonize the decline of spleen/body weight induced by hydrocortisone, increasehemolysin content (HC50), promote the ability of macrophages for celiac macrophageand heighten the delayed hypersensitivity level. Fucoidan fractions had excellenteffect on immune regulation in immunodepression mice. At the same time, there wereno significant differences of the effects on the immune function of mice betweenthem.5. The antiviral effect on influenza virus of different molecular weight fucoidanwas assessed by fluorometric assay of influenza virus neuraminidase in vitro. Both ofthe low and medium molecular weight fucoidan exhibited significantly inhibitoryeffect on the activity of neuraminidase in vitro, especially fractions with mediummolecular weight had better inhibitory activity than low molecular weight fractions. Above all, comparison of digestion and absorption characteristics, immunefunction and antiviral effect on influenza virus with different molecular weightfucoidan fractions from S. japonica not only lay the foundation for in-depth study ofthe structure-activity relationship of molecular weight, structure and activity, but alsoprovide a theoretical base for low molecular fucoidan application, and will contributeto development of fucoidan price increment. |
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