Some structural features of pectic polysaccharide from tansy, Tanacetum vulgare L.

The structure of polysaccharide isolated from tansy, Tanacetum vulgare L. referred to as tanacetan was elucidated by a combination of partial acid hydrolysis, Smith degradation, digestion by a commercial pectinase preparation and NMR spectral analysis of the fragments obtained. They consist of pectin built on a linear backbone of rhamnogalacturonan and the ramified ‘hairy’ regions. The backbone proved to consist of α-1,4-d-galactopyranosyluronan blocks interconnected by 1,2-linked rhamnose residues involved in the linear sugar chain. The hairy regions were shown to contain the following fragments of the backbone: →4)-α-GalpA-(1→2)-α-Rhap-(1→4)-α-GalpA-(1→ and the side chains attached to the residues of rhamnopyranose of these fragments. The single and β-1,4-linked residues of galactopyranose were found to substitute 4-position of α-1,2-linked rhamnose residues of the backbone. In addition, the chains composed of β-1,4-, and 1,6-linked galactopyranose residues as well as the terminal residues of β-galactopyranose, α-arabinofuranose, and 2-mono-O-methyl-β-galactopyranose were detected. Some residues of α-arabinofuranose were shown to be substituted in 2-, 5-, 2,5-, and 3,5-positions, and residues of β-galactopyranose were found to be substituted in 4,6-positions. Some α-1,2-linked rhamnose residues appeared to occupy at the reducing end of the backbone. Smith degradation of the parent tanacetan TVF and of the product of its pectinase digestion led to polysaccharide fragments differed in high contents of the arabinose residues (42.5 and 48.6%, respectively) thus indicating to an occurrence of some ramified regions consisted of the arabinose residues.