Studies on Indian plant gums: composition and graded hydrolysis of gum karaya (Sterculia urens Roxb.)

Gum karaya (Sterculia urens Roxb.) is constituted from L-rhamnose, D-galactose and D-galacturonic acid which appear to be present in the molecular ratio of 4:6:5. D-tagatose, which has been reported to be present in other Sterculia gums, could not be detected in the sample of the karaya gum now examined. The original crude gum contains some acetyl groups also, which get detached during purification. On graded hydrolysis with dilute sulphuric acid under controlled conditions, the gum yields L-rhamnose, D-galactose and a mixture of two aldobiuronic acids