High molecular weight constituents from roots of Echinacea pallida: an arabinogalactan-protein and an arabinan.
This investigation shows structural features of two macromolecules from roots of Echinacea pallida (Nutt.) Nutt: an arabinogalactan-protein (AGP) and an arabinan. The arabinogalactan-protein was precipitated with beta-glucosyl Yariv reagent from a high molecular weight fraction. Investigations of the neutral sugar composition revealed Gal (52.1% w/w) and Ara (38.2% w/w) in a ratio of 1.4:1, accompanied by Glc (6.9% w/w) and Rha (2.8% w/w). The content of uronic acids was 6.2%. Mild acid hydrolysis detects Ara and Glc being located at the periphery of the molecule. Linkage analyses and NMR spectroscopy revealed a backbone of the polysaccharide mainly consisting of 3-linked and 3,6-linked Galp-residues. Side chains are composed of 3,6-linked or 6-linked Galp terminating in 5-linked Araf, terminal Araf, Glcp and GlcAp. The protein part (3.9% w/w) of the AGP is rich in Hyp, Ser, Ala, Thr, Glu, Asp and Gly. The amount of Hyp was determined by a colorimetric method and found to be (0.65% (w/w) of the AGP, which is in good agreement with the result obtained by amino acid hydrolysis (0.67% w/w). The arabinan was isolated from the supernatant of the Yariv precipitation on the basis of solubility in EtOH (80%). It mainly consists of Ara (85.8%). Linkage analyses and NMR spectroscopy indicate a highly branched molecule, consisting of 3,5-linked, 5-linked and terminal Araf-residues in equal amounts.
Thude
Sebastian
S
Institute of Pharmacy, Department of Pharmaceutical Biology, University of Kiel, Gutenbergstr. 76, D-24118 Kiel, Germany. sthude@pharmazie.uni-kiel.de
Classen
Birgit
B
D020900:Echinacea / Q000737:chemistry*; D005685:Galactans / Q000737:chemistry* / Q000302:isolation & purification; D006023:Glycoproteins / Q000737:chemistry*; D010940:Plant Proteins / Q000737:chemistry; D018517:Plant Roots / Q000737:chemistry*; D011134:Polysaccharides / Q000737:chemistry* / Q000302:isolation & purification
D005685:Galactans; D006023:Glycoproteins; D010940:Plant Proteins; D011134:Polysaccharides; C030080:araban; C005653:arabinogalactan