New studies on gum ghatti (Anogeissus latifolia) part II. Structure characterization of an arabinogalactan from the gum by 1D, 2D NMR spectroscopy and methylation analysis
2010; Elsevier BV; Volume: 25; Issue: 8 Linguagem: Inglês
10.1016/j.foodhyd.2010.11.021
ISSN1873-7137
AutoresJi Young Kang, Steve W. Cui, Glyn O. Phillips, Jie Chen, Qingbin Guo, Qi Wang,
Tópico(s)Microbial Metabolites in Food Biotechnology
ResumoThe structure of a water soluble arabinogalactan isolated from gum ghatti (Gatifolia SD) was elucidated by methylation analysis and 2D NMR spectroscopy. The arabinogalactan fraction (F80) was obtained by a sequential ethanol precipitation of gum ghatti (Gatifolia SD). Methylation and GC–MS analysis indicated that F80 was a highly branched polysaccharide; the terminal sugar residues were about 40.8% of the total sugars. The majority of the terminal units were α-l-Araf, with small amounts of T-GlcpA, T-Arap, T-Rhap and T-Galp. About 14.2% of the total sugar residues were →6)-β-d-Galp-(1→ branched at 3rd and 4th positions. The linear portion of the arabinogalactan was composed of →4)-GlcpA(1→, →6)-Galp(1→ and →2)-l-Araf-(1→ linkages. Based on the results from methylation analysis, 1D (1H, 13C) and 2D (COSY, TOCSY, HMQC and HMBC) NMR spectroscopy, the structure of F80 was proposed as follows:Download : Download full-size image R is one of the following groups: →3)-β-d-Galp-(1→, →5)-β-d-Araf-(1→, →2,3-Manp1→, T-α-l-Araf 1→, T-GlcpA1→ and T-l-Arap 1→. Galactose has the -β-D configuration, while the arabinose and rhamnose are in the α-l form.
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