Tagua palm

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). 

When it is ripe, the fruit of the tagua palm splits, and the kernels drop out. The nuts are still soft inside and are edible. They must be carefully dried and possibly fumigated to ensure that they are insect free before they can be worked. They have a tendency to produce a star-shaped crack in the centre as they dry. 

Occurrence. There are many polysaccharides that yield D-mannose on hydrolysis. For preparative purposes, the most important source is the seed of the tagua palm Phytelephas macrocarpa, also known as vegetable ivory.117 Salep mucilage from tubers of Orchidaceae, the seed of Phoenix canariensis, and white spruce hemicellulose are rich enough sources of D-mannose that they have been used for the preparation of this sugar. Konjac flour, which is commonly available in Japan from Amorphophallus konjac, provides another source of this hexose.118... 

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 is a relatively rare sugar, of slight importance in nutrition. It is obtained by acid hydrolysis of its natural polymer, mannosan, found most abundantly in Spruce sawdust and in the vegetable-ivory nut from the Tagua Palm. In concentrations of 0-5 0 per cent, mannose occurs in many higher proteins. 

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. 

The quest for imitations of ivory have led to the use of vegetable ivory, the hard white nuts produced by various tropical trees. The most common of these are the doum palm (Hyphanae thebaica) and the tagua Phytelephas macro-carpa). These nuts have a brown fibrous rind, but the meat inside is homogeneous white or yellowish white. Softer than ivory, these nuts are easy to carve, and are popular for making small items such as netsuke, buttons, beads, and jewelry. 

The form and structure of the nut varies with each species. The doum palm produces fruits the size of small oranges, that each hold one kernel (nut), while the tagua produces fruits the size of human heads, that contain multiple kernels. Both types of kernel are about the size of a chicken s egg. The tagua is the nut most used today. 

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