Structural Characterization,chemical Modifications And Bioactivities Of A Novel Polysaccharide From Lachnum Sp.

In this study,a novel exopolysaccharide from Lachnum YM130(LEP-2a)was prepared through fermentation,extraction and purification,and characterized by monosaccharide composition analysis,methylation analysis,FT-IR analysis and NMR analysis,and its in vitro antitumor activity was evaluated;LEP-2a was acetylated and benzoylated,respectively,and the cardiovascular protective effects of LEP-2a and its derivatives on STZ-induced diabetic mice were studied.High performance gel permeation chromatography(HPGPC)demonstrated that LEP-2a was a homogeneous component with an average molecular weight of 1.61 × 106 Da.The result of monosaccharide composition analysis showed that LEP-2a was composed of mannose and galactose in a molar ratio of 3.8:1.0.The results of methylation analysis,FT-IR analysis and NMR analysis indicated that the backbone of LEP-2a consisted of 1,2-linked-α-D-Manp,1,2,6-linked-α-D-Manp,1,3,4-linked-α-D-Manp and 1,3-linked-β-D-Galp.In vitro antitumor activity assay proved that LEP-2a could significantly enhance the inhibitory effect of 5-Fu on Hela cells at the concentrations of 100,200,300 and 400 μg/mL.LEP-2a was acetylated and benzoylated,respectively,to obtain acetylation of LEP-2a(ALEP-2a)with DS of 0.220 and benzoylation of LEP-2a(BLEP-2a)with DS of 0.574.The results of FT-IR analysis and NMR analysis further confirmed that LEP-2a was acetylated and benzoylated successfully.Based on the result of 13 C NMR analysis,we speculated that C-3,C-4 and C-6 of →2)-α-D-Manp-(1→,C-2,C-3,C-4 and C-6 ofα-D-Manp-(1→,C-3 and C-4 of →2,6)-α-D-Manp-(1→,C-2,C-4 and C-6 of→3,4)-α-D-Manp-(1→,C-1,C-2,C-4 and C-6 of →3)-β-D-Galp-(1→ as well as C-2,C-4 and C-6 of β-D-Galp-(1→ might be partly substituted by acetyl group;C-1 of→3)-β-D-Galp-(1→ was completely benzoylated,and C-4 of →2)-α-D-Manp-(1→,α-D-Manp-(1→ and →2,6)-α-D-Manp-(1→ as well as C-6 of →2)-α-D-Manp-(1→,α-D-Manp-(1→,→3,4)-α-D-Manp-(1→,→3)-β-D-Galp-(1→ and β-D-Galp-(1→might be partially substituted by benzoyl group.Diabetic mice model was established by intraperitoneal injection with streptozotocin(STZ),and the cardiovascular protective effects of LEP-2a,ALEP-2a and BLEP-2a at different doses on diabetic mice were investigated.The results showed that LEP-2a and its derivatives had cardiovascular protective effect in a dose-effect relationship;compared with the model group,the heart,kidney and liver indexes in the treatment groups significantly decreased,the activities of SOD,GSH-PX and CAT in heart significantly increased,and the level of MDA significantly decreased,the levels of AGEs,hs-CRP,sICAM-1 and ET-1 in serum significantly decreased,and the level of NO significantly increased;compared with LEP-2a at same dose,the cardiovascular protective effects of ALEP-2a and BLEP-2a were even more significant.In addition,histopathological observation revealed that the impaired myocardial structure in the treatment groups were improved.In conclusion,the mechanism of the cardiovascular protective effects of LEP-2a and its derivates may be related to improvement of antioxidant defense system,inhibition of oxidative stress and promotion of regeneration of the damaged myocardium.