A simple method for the detection and quantitative determination of hexuronic acids and pentoses

The present report describes a new and simple method for the detection and quantitative determination of pentoses and hexuronic acids either separately or in a mixture. The method involves treatment of the sample with sulfuric acid followed by the addition of harmine and then cysteine. Hexuronic acids produce a pink color with harmine, while pentoses react only after the addition of cysteine. Hexosamines, methylpentoses, and moderate amounts of hexoses do not interfere with these determinations. The method is simple, accurate, and allows the determination of small amounts of pentoses in the presence of larger amounts of hexuronic acids and other sugars.