CHARACTERIZATION OF ANADENANTHERA-MACROCARPA EXUDATE POLYSACCHARIDE

Exudate gum from Anadenanthera macrocarpa Benth. trees was purified an d fractionated using 0.1 M aq. NaCl/ethanol as a solvent/non-solvent s ystem. The composition of the polysaccharide was determined as 67% ara binose, 24% galactose, 2% rhamnose and 7% glucuronic acid, by a combin ation of high performance liquid chromatography of fully hydrolysed gu m and colorimetric analysis of uronic acid. Molecular characteristics of the polysaccharide and its fractions were investigated by light sca ttering intensity, dilute solution viscometry and gel permeation chrom atography (GPC). The whole gum was shown to possess a broad molar mass distribution with (M) over bar(W) = 3.7 x 10(6) g mol(-1) and [eta] = 11 cm(3) g(-1). Hydrodynamic properties indicated a highly branched s tructure. Fractions were obtained covering a range of molar masses. Th e intrinsic viscosity in 1.0 M aq. NaCl at 25 degrees C was found to d epend on molar mass according to: [eta]/cm(3) g(-1) = 0.0145 M-0.44. T he hydrodynamic volume parameter [eta]M gave a common GPC calibration for branched polysaccharide fractions and linear poly(oxyethylene) sta ndards.