A NEW FAMILY OF OLIGOSACCHARIDES FROM THE XYLOGLUCAN OF HYMENAEA COUBARIL L. (LEGUMINOSAE) COTYLEDONS

The xyloglucan from cotyledons of Hymenaea courbaril was hydrolysed wi th endo-(1,4)-beta-D-glucanase (cellulase) and analysed by TLC and HPA EC. The limit digest was different from those obtained from xyloglucan s of Tamarindus indica and Copaifera langsdorffii. On treatment with n asturtium beta-galactosidase, two main oligosaccharides were detected by TLC and HPAEC. Using a process of enzymatic sequencing involving al ternate treatments with a pure xyloglucan oligosaccharide-specific alp ha-xylosidase, and a pure beta-glucosidase, both from nasturtium, thei r structures were deduced to be XXXG and a new oligosaccharide XXXXG. These structures were confirmed by H-1 NMR. The relative proportions o f XXXG and XXXXG indicate that approximately half of the subunits in H ymenaea xyloglucan are based on the new oligosaccharides. In the nativ e polymer the XXXXG subunits are likely to carry galactosyl substituen ts in varying proportions, since cellulase hydrolysates contained many bands which were converted to XXXXG on hydrolysis with nasturtium bet a-galactosidase. Although no comparative studies on the physico-chemic al properties of Hymenaea courbaril xyloglucan have yet been performed , our results indicate that this polymer is less interactive with iodi ne when compared with T. indica and C. langsdorffii xyloglucans, sugge sting that changes in conformation may occur due to the presence of XX XXG. (C) 1997 Elsevier Science Ltd.