| Active oxygen radicals in the human body have a strong effect on lipidperoxidation and cause various diseases as a result of oxidative imbalance. Naturalpolysaccharides as antioxidants have attracted much attentions nowadays due to theiradvantages of non-toxicity and excellent biocompatibility, compared to chemicalsynthetic drugs, yet research on antioxidant activity of natural polysaccharides and themechanism is still in the exploratory stage. In view of the above, in vitro evaluation ofantioxidant activity of plant derived inulin (In), animal derived chitosan (Cs) andfungi derived ganoderma lucidum polysaccharides (Glp) was carried out both inchemical and cell method, aiming at exploring the relationship between their structureand antioxidant activity and revealing the possible mechanism in cellular andmolecular level.Firstly, in vitro chemical experiment was made to evaluate antioxidant abilitiesof In, Cs and Glp in comparison with ascorbic acid by the scavenging ability ofDPPH, O―2and OH free radical. IR and GPC were employed to analyze thestructure and molecular weight of three kinds of natural polysaccharides. Therelationship between their structure and antioxidant ability was discussed, andusability and stability of different free radical methods for studying in vitroantioxidant ability of natural polysaccharides were also investigated.Results showed that the order of DPPH scavenging ability was: Vc> Cs> In>Glp, which is associated with their structure. The order of O—2scavenging abilitywas In> Glp> Cs> Vc. Both ascorbic acid and chitosan could react with thechromogenic agent directly or indirectly, and thus there are some errors in the O—2method. The order of OH scavenging ability was Vc> Cs> In> Glp. Furtherresearches showed that ascorbic acid could promote while In, Cs and Glp inhibitedthe production of OH.Secondly, in vitro cellular experiment was made to explore the toxicity effect ofdifferent doses of natural polysaccharides in comparison with ascorbic acid on normalHepG2cells and their performance of repairing oxidative damaged HepG2cells wasalso determined, employing celluar activity and morphology, activity of SOD andGSH-Px and level of MDA as evaluation indexes.Results showed that using50μM H2O2to damage HepG2cells for2h was afeasible way to establish oxidation damage model. Both three polysaccharides and ascorbic acid were non-toxic and could repair oxidative damage in cell morphology aswell as improve cell viability. Thereinto, middle dose of Vc, low dose of In, middledose of Cs and middle dose of Glp showed good performance in improving cellactivity and decreasing the MDA level in oxidative damaged HepG2cells andcompared with middle dose of Vc, the other three worked better in improving theactivity of GSH-Px. As a comprehensive result of all the evaluation indexes in thecellular experiment, middle dose of Glp showed the best antioxidant properties inimpairing oxidative damaged HepG2cells.Compared to in vitro chemical experiment, cellular experiment could moreaccurately reflect the antioxidant activity of natural polysaccharides in repairing theoxidative damaged HepG2cells. |
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