Structural elucidation of a new arabinogalactan from the leaves of Nerium indicum.
A polysaccharide fraction, NIB-2, was obtained from the 3% aqueous sodium carbonate extract of Nerium indicum leaves using anion-exchange chromatography and gel-permeation chromatography. It was found to be composed of rhamnose, arabinose, galactose, in the ratios of 1.0:10.4:4.4, along with 4% of galacturonic acid. The results of methylation analysis, periodate oxidation, partial acid hydrolysis, pectinase treatment, and 13C and 1H NMR spectroscopy indicate that it is mainly an arabinogalactan having a backbone of 1,6-linked beta-Galp, with branches at O-3, consisting of terminal, 1,5-, and 1,3,5-linked arabinofuranosyl residues, and a small proportion of galactosyl residues at the termini. Rhamnose and galacturonic acid arose from a contaminating rhamnogalacturonan.
Dong
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Shanghai Institute of Materia Medica, Chinese Academy of Sciences, People's Republic of China. dongqun@hotmail.com
Fang
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D005685:Galactans / Q000737:chemistry*; D019684:Magnoliopsida / Q000737:chemistry*; D019906:Nuclear Magnetic Resonance, Biomolecular; D018515:Plant Leaves / Q000737:chemistry*; D010947:Plants, Toxic / Q000737:chemistry*
D005685:Galactans; C005653:arabinogalactan