Structural characterization of hemicelluloses fractionated by graded ethanol precipitation from Pinus yunnanensis

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• 作者：Bai-Liang Xue^a ; Jia-Long Wen^a ; Feng Xu^a ; ^{rcsun3@bjfu.edu.cn} ; Run-Cang Sun^a ; ^b ; ^{rcsun3@bjfu.edu.cn}
• 关键词：Pinus yunnanensis ; Hemicelluloses ; Characterization ; FT-IR ; NMR ; HSQC
• 刊名：Carbohydrate Research
• 出版年：2012
• 期刊代码：15_00086215
• 类别：ch
• 出版时间：1 May, 2012
• 卷：352
• 期：Complete
• 页码：159-165
• 文件大小：641 K

摘要

Fractionation of hemicelluloses from delignified Pinus yunnanensis was carried out with KOH/H₃BO₃ solution followed by graded precipitation in 15%, 60%, and 90%(v/v) ethanol solutions, respectively. Chemical compositions, physicochemical properties, and structures of the precipitated hemicellulosic fractions were elucidated by a combination of sugar analysis, GPC, FT-IR, and ¹H, ¹³C and 2D HSQC NMR spectroscopy. Sugar analysis showed that the hemicellulosic fraction precipitated by 15%ethanol solution (H₁) had a predominance of xylose (58.52%), while mannose was the major sugar component in the hemicellulosic fractions precipitated by 60%(H₂) and 90%(H₃) ethanol solutions. GPC results revealed that the hemicelluloses precipitated by low concentration of ethanol solutions had higher weight-average molecular mass (50,090-79,840 g/mol) than those obtained in the high concentration of ethanol solutions (16,500 g/mol). The fraction precipitated by 60%ethanol solution (H₂) was composed of d-galactose, d-glucose and d-mannose in a ratio of approximately 1:1:3.5. Structural determination indicated that the hemicellulosic fraction (H₂) had a main structure of (1鈫?)-linked 尾-glucomannans backbone with (1鈫?)-linked 伪-d-galactose as a side chain attached to C-6 of mannose units. In addition, this fraction also contained minor amounts of xylans.