Pectin Isolated from the Midrib of Leaves of Nicotiana tabacum

Abstract

A pectin isolated from tobacco midrib contained residues of D-galacturonic acid (83.7 %), L-rhamnose (2.2%), L-arabinose (2.4%) and D-galactose (11.2%) and small amounts of d-xylose and D-glucose. Methylation analysis of the pectin gave 2, 3, 5-tri- and 2, 3-di-O-methyl-L-arabinose, 3, 4-di- and 3-O-methyI-L-rhamnose and 2, 3, 6-tri-O-methyl-D-galactose. Reduction with lithium aluminum hydride of the permethylated pectin gave mainly 2, 3-di-O-methyl-D-galactose and the above methylated sugars. Partial acid hydrolysis gave homologous series of β-(l→4)-linked oligosaccharides up to pentaose of D-galactopyranosyl residues, and 2-O-(α-D-galactopyranosyluronic acid)-L-rhamnose, and di- and tri-saccharides of α-(1→4 linked D-galactopyranosyluronic acid residues. These results suggest that the tobacco pectin has a backbone consisting of α-(l→4)-linked D-galactopyranosyluronic acid residues which is interspersed with 2-linked L-rhamnopyranosyl residues. Some of the L-rhamnopyranosyl residues carry substituents on C-4. The pectin has long chain moieties of β-(1→4)-linked D-galactopyranosyl residues. © 1980, Japan Society for Bioscience, Biotechnology, and Agrochemistry. All rights reserved.