Pectic substances. I. The major pectin from the fruits of Zizyphus jujuba Miller var. inermis Rehd.

Abstract

The major acidic polysaccharide, named Zizyphus-pectin A, was isolated from the fruits of Zizyphus jujuba MILLER var. inermis REHD. The final preparation was homogeneous as determined by ultracentrifugal analysis, cellulose acetate and glass-fiber electrophoresis, and gel chromatography. It was composed of D-galacturonic acid, L-rhamnose, D-galactose, and L-arabinose in the molar ratio of 35 : 1 : 1 : 4, and its molecular weight was estimated to be 263000. The major part (58%) of D-galacturonic acid exists as the methyl ester. O-Acetyl groups were identified and the content amounted to 2.3%. Partial acid hydrolysis gave 2-O-(α-D-galactopyranosyluronic acid)-L-rhamnose, and di- to penta- saccharides consisting of α-1→4-linked D-galactopyranosyluronic acid units. In addition, reduction of carboxyl groups followed by methylation analysis showed that the pectin possesses a backbone chain consisting of α-1→4-linked D-galactopyranosyluronic acid residues which are interspersed with α-1→2-linked L-rhamnopyranose residues having side chains at position 4. The pectin has β-1→4-linked D-galactopyranosyl linear side chains and α-1→5-linked L-arabinofuranosyl highly branched side chains having 1→3-linked branching points.