Abstract
A pectic polysaccharide was prepared from the cotyledons of kidney beans. It consisted of galacturonic acid, arabinose, xylose, fucose, galactose, rhamnose and mannose. The xylose content was quite high with a molar ratio of xylose-to-galacturonic acid of 1:2. The molar percentage of uronic acid in the pectic polysaccharide was 39.6%. The percentage of esterification of the galacturonic acid residue was 41.4%.
The pectic polysaccharide was oxidized with sodium periodate and subjected to controlled Smith degradation. By this treatment almost all xylose and some arabinose were removed, and an acidic polysaccharide was formed from the pectic polysaccharide. In contrast to the pectic polysaccharide, the obtained acidic polysaccharide was degraded in hot neutral solutions by a transelimination mechanism similar to commercial citrus pectin preparations.
The solution of acidic polysaccharide was heated in a boiling water bath at pH 6.8, and the products were separated by gel filtration into two fractions. One was a low molecular weight uronide fraction, and the other was a neutral sugar rich fraction, indicating that the pectic polysaccharide of kidney bean cotyledons possessed neutral sugar blocks of arabinose and galactose much like citrus pectin.
