A new family of oligosaccharides from the xyloglucan of Hymenaea courbaril L. (Leguminosae) cotyledons

The xyloglucan from cotyledons of Hymenaea courbaril was hydrolysed with endo-(1,4)-β-d-glucanase (cellulase) and analysed by TLC and HPAEC. The limit digest was different from those obtained from xyloglucans of Tamarindus indica and Copaifera langsdorffii. On treatment with nasturtium β-galactosidase, two main oligosaccharides were detected by TLC and HPAEC. Using a process of enzymatic sequencing involving alternate treatments with a pure xyloglucan oligosaccharide-specific α-xylosidase, and a pure β-glucosidase, both from nasturtium, their structures were deduced to be XXXG and a new oligosaccharide XXXXG. These structures were confirmed by 1H NMR. The relative proportions of XXXG and XXXXG indicate that approximately half of the subunits in Hymenaea xyloglucan are based on the new oligosaccharides. In the native polymer the XXXXG subunits are likely to carry galactosyl substituents in varying proportions, since cellulase hydrolysates contained many bands which were converted to XXXXG on hydrolysis with nasturtium β-galactosidase. Although no comparative studies on the physico-chemical properties of Hymenaea courbaril xyloglucan have yet been performed, our results indicate that this polymer is less interactive with iodine when compared with T. indica and C. langsdorffii xyloglucans, suggesting that changes in conformation may occur due to the presence of XXXXG. The xyloglucan from cotyledons of Hymenaea courbaril was hydrolysed with endo-(I → 4)-β-d-glucanase (cellulase) and analysed by TLC and HPAEC. The limit digest was different from those obtained from xyloglucans of Tamarindus indica and Copaifera langsdorffii. On treatment with nasturtium β-galactosidase two main oligosaccharides were detected. Using enzymatic sequencing involving alternate treatment with pure xyloglucan oligosaccharide specific α-xylosidase, and pure β-glucosidase, both from nasturtium, their structures confirmed by 1H NMR were XXXG and a new oligosaccharide XXXXG. The relative proportions of XXXG and XXXXG indicate that half the subunits in Hymenaea xyloglucan are based on XXXXG. In the native polymer XXXXG carries galactosyl substituents in varying proportions, since cellulase hydrolysates contained many bands converted to XXXXG on hydrolysis with nasturtium β-galactosidase. Our results indicate that this polymer is less interactive with iodine following conformation changes owing to XXXXG.