CHAPTER 3 - PLANT GUMS AND MUCILAGES

Abstract

Gum acacia, gum tragacanth, gum ghatti, gum myrrh, agar, carragheen and alginic acid are gums and mucilages of pharmaceutical importance. This chapter discusses the structure and uses of these plant gums and mucilages. The plant gums are polysaccharide-containing exudations that form after injury to certain trees and fruits. These injuries are often mechanically produced, and attack by organisms at the site of the wound causes formation of the gum. Plant mucilages, on the other hand, generally occur naturally in various parts of the plants and act as food reserves or as a means of storing water. The plant gums are acidic materials and generally exist in the plant as neutral salts. They are hydrophilic; in cold water they either dissolve or form mucilage. A common method of purification is to add a solution of the gum in dilute hydrochloric acid to ethanol when the gum acid precipitates. Chemically, these substances are complex and contain many sugar residues united by various types of glycosidic linkage. Except for tragacanth, all common plant gums yield D-glucuronic acid on hydrolysis.