Abstract
Background
Hedera nepalensis is a traditional medicinal plants, and the dried leaves of it are generally used for the cure and treatment of many diseases, also widely known as Chang-Chun-Teng in Chinese. Until now, structural characterization of water-soluble polysaccharides isolated from leaves of Hedera nepalensis have been scarcely studied, even though the chemical compounds derived from it and their biological activities have been widely studied.
Methods
Water-soluble polysaccharides (WHNP) were isolated from the dried leaves of Hedera nepalensis, and their structural features were investigated. One neutral polysaccharide fraction (WHNP-N) and three major pectin fractions (WHNP-A2b, WHNP-A2c and WHNP-A3b) were obtained from WHNP, respectively. There was no analysis of the neutral fraction (WHNP-N), while the structural characterization of three major pectin fractions (WHNP-A2b, WHNP-A2c and WHNP-A3b) were further studied by monosaccharide composition, HPGPC, NMR and methylation analyses.
Results
The results indicated that two fractions WHNP-A2b (Mw = 45.8 kDa) and WHNP-A3b (Mw = 58.6 kDa) were mainly composed of rhamnogalacturonan I (RG-I). In WHNP-A2b, RG-I domains primarily substituted with α-L-1,5/1,3,5-arabinan, type II arabinogalactan (AG-II), β-D-1,4-galactan and/or type I arabinogalactan (AG-I) as side chains, while RG-I-type pectin of WHNP-A3b mainly branched with α-L-1,5/1,3,5-arabinan, β-D-1,4-galactan and AG-II side chains. WHNP-A2c (Mw = 12.4 kDa) was primarily comprised of galacturonic acid (GalA, 60.8%), and enzymatic analysis indicated that this fraction mainly consisted of rhamnogalacturonan I (RG-I), rhamnogalacturonan II (RG-II) and homogalacturonan (HG) domains with mass ratios of 1.8:1.0:0.6. On the other hand, WHNP-A2c was found to be rich in RG-I domains, which contained α-L-1,5/1,3,5-arabinan, AG-II, β-D-1,4-galactan and/or AG-I as side chains. The HG domains of WHNP-A2c was released in the form of un-esterified and partly methyl-esterified and/or acetyl-esterified oligogalacturonides with a 1 to 7 degree of polymerization after endo-polygalacturonase degradation.
Conclusion
Our results reveal the structural characteristics of these polysaccharide fractions, which will contribute to elucidating their structure–activity relationships.
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Details
1 Northeast Normal University, Engineering Research Center of Glycoconjugates of Ministry of Education, Jilin Provincial Key Laboratory On Chemistry and Biology of Changbai Mountain Natural Drugs, School of Life Sciences, Changchun, China (GRID:grid.27446.33) (ISNI:0000 0004 1789 9163)