OLIGOSACCHARIDES DERIVED FROM THE XYLOGLUCAN ISOLATED FROM THE SEEDS OF HYMENAEA COURBARIL VAR STILBOCARPA

On aqueous extraction, Hymenaea courbaril var. stilbocarpa, known in B razil as jatoba, furnishes a high yield of viscous xyloglucan (45%) fr om its seeds. The crude polysaccharide (B1) was hydrolysed and the pro ducts, analysed as alditol acetates, were glucose, xylose, galactose a nd arabinose in the ratio 50:35:13:2. After further fractionation on a DEAE-cellulose column (chloride form), the main fraction (70% yield, B2) was obtained. The basic structure of the xyloglucan was determined as a cellulose-type (1-->4)-linked beta-D-glucan backbone partially s ubstituted with side chains at O6 of alpha-D-xylopyranose, some of whi ch were themselves substituted at O2 by the units of beta-D-galactopyr anose. Treatment of the xyloglucan (B2) with commercial cellulase from Trichoderma sp. yielded six oligosaccharides. These oligosaccharides were isolated by preparative paper chromatography, and their structure s were determined by gas-liquid chromatography-mass spectroscopy of th e derived partially O-methylated alditol acetates. These results confi rm the structure proposed for jatoba seed xyloglucan.