Structural studies with tobacco pectins

Abstract

The structures of three polysaccharides have been investigated, pectin and reduced pectin from cured leaf stems of Bright Virginia tobacco, and pectin from fresh leaves of Virginia tobacco plants. The hydrolysis products from cured tobacco pectin have been examined and the main components characterised and determined quantitatively. This pectin has an anhydrogalacturonic acid content of more than 90%. The polysaccharide has been subjected to periodateoxidation and to partial hydrolysis with a pectinase preparation. The latter yielded di-, tri- and tetra-galacturonic acids and the linkages in these compounds have been shown to be alpha-1,4. Diborane has been used to reduce the polysaccharide and the resultant material has been methylated and hydrolysed and the products characterised by vapour phase chromatography. The anhydrouronic acid content of pectin from fresh leaves is much lower (ca. 20%) and unlike the "cured pectin" readily yields aldobiouronic acids on partial hydrolysis with dilute mineral acids. The structures of three of these hydrolysis products have been examined. The chromatographic behaviour of D-galacturonic acid, the effect of sodium borohydride on two uronic acid derivatives and the effect of bromine and sulphuric acid on tartaric acids have been examined inrelation to the analytical work which was carried out with the pectins.