title: Structure and antioxidant activity of a novel poly-N-acetylhexosamine produced by a medicinal fungus.
abstract: A novel poly-N-acetylhexosamine (polyhexNAc) about 6 kDa average molecular weight (MW) was isolated from the low-MW fraction of exopolysaccharide produced by liquid fermentation of a medicinal fungus Cordyceps sinensis Cs-HK1. The composition and linkage of sugar residues were determined by mass spectrometry and methylation analysis, and the anomeric configuration and chain linkage were confirmed by NMR. From the analytical results, the molecular structure was elucidated as a [-4-β-D-ManNAc-(1→3)-β-D-GalNAc-(1→] disaccharide repeating unit in the main chain with a Gal branch occurring randomly at the 3-position of ManNAc. This polyhexNAc showed notable antioxidant activities with a Trolox equivalent antioxidant capacity of 330 μmol Trolox/g, a ferric reducing ability of plasma of 45.7 μmol Fe(II)/g, and significant cytoprotective effect against H2O2-induced PC12 cell injury. This is the first report on the structure and bioactivity of an extracellular amino-polysaccharide from the Cordyceps species.
authors.affiliation: Department of Applied Biology & Chemical Technology, State Key Laboratory of Chinese Medicine and Molecular Pharmacology in Shenzhen, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong.
authors.forename: Shiguo
authors.initials: S
authors.lastname: Chen
authors.forename: Ka-Chai
authors.initials: KC
authors.lastname: Siu
authors.forename: Wen-Qiang
authors.initials: WQ
authors.lastname: Wang
authors.forename: Xing-Xun
authors.initials: XX
authors.lastname: Liu
authors.forename: Jian-Yong
authors.initials: JY
authors.lastname: Wu
mesh_terms: D000818:Animals; D052160:Benzothiazoles / Q000737:chemistry; D002240:Carbohydrate Sequence; D032661:Cordyceps / Q000737:chemistry*; D016166:Free Radical Scavengers / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D005609:Free Radicals / Q000737:chemistry; D062610:Fungal Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D006595:Hexosamines / Q000737:chemistry* / Q000302:isolation & purification / Q000494:pharmacology; D009682:Magnetic Resonance Spectroscopy; D008516:Medicine, Chinese Traditional; D008745:Methylation; D008969:Molecular Sequence Data; D008970:Molecular Weight; D016716:PC12 Cells; D051381:Rats; D017550:Spectroscopy, Fourier Transform Infrared; D013451:Sulfonic Acids / Q000737:chemistry; D053719:Tandem Mass Spectrometry
chemical_list: D052160:Benzothiazoles; D016166:Free Radical Scavengers; D005609:Free Radicals; D062610:Fungal Polysaccharides; D006595:Hexosamines; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid