Gum heteropolysaccharide and free reducing mono- and oligosaccharides of Anadenanthera colubrina

The gum contains poly- mono- and oligosaccharides. The monos and oligos (A-F) have structures similar to those of the side-chains of the polysaccharide (Gal main-chain). The gum from Anadenanthera colubrina consists mainly of a complex high-arabinose heteropolysaccharide with a (1 → 3)-linked β-d-Gal p main-chain and many different side-chains. These contain β-d-Gal p-[(1 → 6)- β-d-Gal p] m -(1 → 6)-, substituted in turn at O-3 by α- l-Araƒ-[(1 → 3)-α- l-Araƒ-] 0−2 . Also present are (1) main-chain units substituted at O-4 and O-6 by α- l-Araƒ units, (2) side-chains of Rha p-(1 → 4)- β-d-Glc pA-(1 → 6)- β-Gal p- groups, (3) α-l-Ara p non-reducing end-units linked (1 → 6) to d-Gal p, and (4) β- Araƒ and β-Ara p structures. For the first time, a plant gum exudate was found to contain in the natural state, reducing low M r carbohydrates. These were rhamnose (0.6%), arabinose (4.7%), mannose (0.1%), galactose (0.8%) and many oligosaccharides (0.6%; 11 with different R F s, with the majority containing arabinose). They were all mixtures with the exception of α-Rha p-(1 → 4)- β-d-Glc pA-(1 → 6)- αβ-Gal and an incompletely identified hexasaccharide, probably having α- l-Araƒ-(1 → 4)-β- d-Galp- and -α- l-Araƒ-(1 → 3)-β- d-Galp- structures. The mono- and oligosaccharides do not appear to arise via in situ autohydrolysis of the gum.