Colorimetric Determination of 3,6-Anhydrogalactose with the Indolyl-3-acetic Acid Reagent

Abstract

THE sugar 3,6-anhydrogalactose is a major constituent of the agarose fraction of agar, of kappa carrageenin, and of some other polysaccharides from marine algae¹. This sugar can be determined spectrophotometrically as 5-hy-droxymethyl-2-furaldehyde² or by an adaptation of the rosorcinol test for ketoses³. The rate of degradation of 3,6-anhydrogalactose to 5-hydroxymethyl-2-furaldehyde suggests that any method used for the colorimetric determination of fructose should be applicable to 3,6-anhydrogalactose. Steinitz⁴ compared six methods for the determination of fructose in body fluids, and favoured the method of Heyrovsky⁵, who used β-indolylacetic acid as the colour reagent. The present communication describes the use of this reagent for the determination of 3,6-anhydrogalactose.