Chemical Modifications And Biological Activities Of A Polysaccharide From Lachnum Sp.

Natural polysaccharides are best resources for supplements and pharmaceuticals that have received more and more attention over recent years.Chemical modification is a type of molecular modification which plays a dominant role in improving the overall utilization of polysaccharide and provides an opportunity to obtain new pharmacological agents with possible therapeutic properties.The aim of this study is to increase the bioactivities of the polysaccharide by different chemical modifications and lay some theoretical foundations for the study of structure-function relationship for a better understanding of the functional effects of Lachnum polysaccharides as well as the development of polysaccharide as functional foods and natural medicine.Lachnum is a kind of saprophytic fungi and more than 250 species of Lachnum are widely distributed throughout the world.Lachnum YM281 polysaccharide(LEP-1b)is a homogeneous component of exopolysaccharide with Mw(molecular weight)4.02×10⁴ g^-mol with the structure of(1?3)?-D-glucan with branch chains(1?3)and(1?6)?-D-glucan.Hyperlipidemia is one of the major health problem people suffering throughout the world,which is also a major risk factor for chronic heart disease that can lead to death.The current study was designed to investigate antihyperlipidemic and hepatoprotective activity of LEP-1b and its selenium modified derivative SeLEP-1b on high-fat induced mice model,to study whether selenylation can improve antihyperlipidemic and hepatoprotective effects or not.Nitric acid-sodium selenite(HNO₃–Na₂SeO₃)method was used to selenize pure LEP-1b.The content of Se in SeLEP-1b was 3.6 mg/g.FT-IR analysis confirmed the introduction of–Se(O)OH group into the LEP-1b,and ¹³C NMR results confirmed the modification of LEP-1b into SeLEP-1b.The main structure of SeLEP-1b was similar to the original structure of native LEP-1b and–Se(O)OH group was attached to the O-6 position of C-6 in LEP-1b.Oral administration of LEP-1b and SeLEP-1b at high dose of 200 mg/kg notably reduced the serum and liver lipids,atherogenic index,and enhanced the activities of antioxidant enzymes of hyperlipidemic mice,as well improved the histopathological status of hepatic tissues.Hence,SeLEP-1b showed better effects than LEP-1b at the same doses.SeLEP-1b demonstrated promising lipid-lowering and liver protecting activities,which may be considered as a novel compound to treat hyperlipidemia and also act as a hepatoprotective agent.Moreover,the present study was also planned to evaluate the anti-fatigue activity of LEP-1b and its carboxymethylated derivative CLEP-1b from the same sp.of Lachnum YM281.Carboxymethylation was confirmed through FT-IR and ¹³C NMR spectroscopies,which showed that the(–CH₂COOH)group was attached to an oxygen(O)atom of the hydroxyl group on(C-3)of LEP-1b.Carboxymethylation of CLEP-1b played a significant role against fatigue,induced by(weight loaded)swimming test in mice.Results of the fatigue related biochemical markers showed that LEP-1b and CLEP-1b at doses of 50,100,200 mg/kg/d,respectively,increased the content of hepatic glycogen and decreased the contents of serum urea nitrogen and lactic acid.Additionally,LEP-1b and CLEP-1b enhanced the endogenous cellular antioxidant enzymes'activities and reduced the lipid peroxidation.Moreover,results revealed that CLEP-1b had higher anti-fatigue activity than LEP-1b at same doses but without statistical significance,especially CLEP-1b high-dose had strong anti-fatigue effects on mice.Therefore,LEP-1b and CLEP-1b can potentially be exploited as a kind of healthcare compound to recover fatigue and to increase physical strength.