Characterization on alduronic acids structure of pectin in flue-cured tobacco using a solid-state NMR method
The content distribution of pectin alduronic acids structure in tobacco leaves has an important impact on its physiological function and product quality. A quantitative analysis method was developed for characterizing the alduronic acids structure of pectin in flue-cured tobacco samples by solid state 13C CP/MAS NMR,using dimethyl silicone rubber tube as the internal standard substance. The C-6 carbon region of pectin in the NMR spectrum was selected,and the deconvolution of spectral peaks was performed using the PeakFit software to achieve the qualitative and quantitative analysis of different alduronic acid unit structures of pectin in tobacco samples,such as carboxylic acid group (-COOH),methyl ester group (-COOCH3) or carboxylate anion group(-COO-). The results,applied to the measurement of pectin content and the structural characteriza-tion of the alduronic acid units in nine tobacco samples from different parts of the tobacco leaf,showed that the pectin content of the tobacco leaf increased gradually with the rise of the tobacco parts. The distribution of methylated pectin content in the sample tobacco leaves was less than 50％,which was low methylated pectin. In contrast to the central tobacco leaves,the upper leaves showed high methylated pectin content,while the lower leaves showed high calcium pectate content. The result provides an accurate and simple technical method for the study of the relationship between the structure and properties of tobacco pectin macromolecules.
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维普
