Estimation of uronic acids using diverse approaches and monosaccharide composition of alkali soluble polysaccharide from Vitex negundo Linn.

Vitex negundo L. is one of the most important species in traditional system of medicine to cure various ailments. Alkali soluble polysaccharide (ASP) from V. negundo stems was isolated and purified in 0.61% yield. Complete hydrolysis of ASP followed by paper chromatography and GLC analysis indicated the presence of l-rhamnose, l-arabinose, d-xylose, d-galactose and d-glucose in mole percent of 1.28, 2.25, 73.49, 8.08, 8.11 along with 2.48 d-galacturonic acid and 4.27 d-glucuronic acid. Uronic acids were also estimated by spectrophotometric methods using carbazole, m-hydroxydiphenyl and 3, 5-dimethyl phenol (DMP) as colorimetric reagents. Estimation of uronic acids using DMP corroborated the results of GLC analysis. The study evaluated the utility of colorimetric methods for uronic acid estimation in polysaccharide having interferences from neutral sugars especially xylose, glucose and galactose. The analysis also resulted in composition of constituent monosaccharides of ASP and co-relation analysis of uronic acids content. The results may divulge the structural moiety of the polysaccharide responsible for its bio-efficacy.