Vegetable ivory, mannan

Mannans (Tagut Nut, Corajo, Vegetable Ivory, Carobean), (CgHioOg, mw 162.14. Poly-, meric polysaccharides which yield mannose on hydrolysis. They can be acetylated and nitrated... 

Mannans and glucomannans from plant sources all contain linear chains of (1 —> 4)-linked d-D-mannose and /J-D-glucose residues as their main structural features. The only true mannans (that is, polysaccharides containing 95% or more of D-mannose residues) so far examined from land plants are those from vegetable ivory (Phytelephas macrocarpa).90 96 The... 

The actual state of the xylans and glucomannans in the living tree is still largely unknown. Since they do not crystallize readily without some chemical modification, such as partial depolymerization or removal of side chains, or both, it would seem likely that they occur in the amorphous state in the wood. The possibility that they could form microfibrils, as does mannan B in vegetable ivory, cannot be entirely excluded.More probably, however, they occur as a powder between and around the cellulose microfibrils. Using a polarized infrared technique, Marchessault and coworkers have obtained indications that, not only the cellulose, but also the xylans and glucomannans, may be oriented in the direction of the fiber axis in wood. 

Mannans. A variety of other polysaccharides may occur in the cell walls of land plants. Among these are mannans, galactans, and pectic substances. In general, softwoods contain approximately 11% combined D-mannose, whereas hardwoods contain only about 1 %. A linear mannan is also the chief constituent of the thickened cell walls of palm seeds, where it occurs as a food reserve and disappears on germination. A rich source is the endosperm of the tagua palm which is known as vegetable ivory and from which buttons have been made. This mannan is a linear chain of D-mannopyranose... 

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