Tagua palm mannan

Mannans, in which mannose units are linked predominantly in j8-d-(1—>4) bonds, are found in the red seaweed Porphyra umbilicalis, in the seed of the tagua palm (Phytelephas macrocarpa) in the form of massive thickening of the cell walls of the endosperm, and in the endosperm of members of the Umbelliferae and of the Compositae (e.g., lettuce seed). 

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... 

D-Mannose 132° + 15 Phenylhydrazone>2 199- 200° Small amounts in sphagnum moss and in peat Mannans Tagua palm seed, Phyte-lephas macrocarpa, tubers of Orchidaceae and in red seaweed, Porphyra spp. 

The presence of mannans in the crude cellulose of softwoods has frequently been reported but it is probable that in most of these instances the polysaccharide involved is a glucomannoglycan (see p. 225). A true mannan (ivory nut mannan) forms about 60% of the endosperm of the seed of the tagua palm [Phytelephas macrocarpa) and its X-ray diffraction pattern resembles that of cellulose. The D-mannose units are mainly /S-D-(i -> 4)-linked in a linear molecule. Similar mannans are found in the tubers of some Orchidaceae species (salep mannan) and in the green coffee bean. 

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