28 



CARBOHYDRATES 



TABLE 2. SUGAR COMPONENTS OF SOME PLANT GUMS AND MUCILAGES 



GUMS 



Name 



Source 



Hydrolysis Products 



Gum arable 

 Mesquite gum 

 Cherry gum 



Acacia 

 Prosopis spp. 

 Prunus spp. 



D-galactose, L-arabinose, 

 L-rhammose, D-glucuronic acid 



L-arabinose, D-galactose, 

 4-O-methyl-D-glucuronic acid 



L-arabinose, D-xylose, D-mannose, 

 D-galactose, D-glucuronic acid 



MUCILAGES 



Flaxseed 

 Mucilage 



Blond Psyllium 

 Mucilage 



Slippery elm 

 Mucilage 



Linum spp. 

 Plantago spp. 

 Ulmus fulva spp. 



D-xylose, L-galactose, L-rhamnose, 

 D-galacturonic acid 



D-xylose, L-arabinose, L-rhamnose, 

 D-galacturonic acid 



D-galactose, 3-O-methyl-D- 

 galactose, L-rhamnose, D-galacturonic 

 acid 



Low molecular weight carbohydrates may be obtained from the 80% ethanol super- 

 natant prepared as described above; or if only these carbohydrates are of interest, they 

 may be extracted immediately from plant material using ethanol sufficient to give a con- 

 centration of 80% when diluted by whatever water is present. Some components (e. g. 

 diphosphates) are strongly bound to tissue and must be extracted with 20% ethanol or other 

 solvents. Ionic substances (salts, amino acids, organic acids) are best removed by ion 

 exchange resins although strongly basic or acidic resins may have some effect on the 

 sugars. Sugar acids and phosphates will be removed by anion exchange resins but may be 

 separated from non-carbohydrate components either by appropriate fraction cutting, or, 

 in the case of phosphates, by precipitation with barium hydroxide and conversion to sodium 

 salts. 



Special methods may be available for purification of the remaining neutral sugars. 

 If one is in large excess, simple concentration of the solution may allow it to crystallize. 

 If the desired component is not metabolized by yeast, impurities can frequently be re- 

 moved by yeast fermentation. 



The most general method for purification of the neutral sugars and derivatives is 

 column chromatography using such adsorbents as charcoal, cellulose powder, starch and 

 Florex, with rather polar developing solvents such as lower alcohols and mixtures of 

 them with water. (See review by Binkley, 22.) On addition of borate, polyhydroxy com- 

 pounds form anionic borate complexes which may be separated on a column of anion ex- 

 change resin using borate buffers as eluants. After elution, cations are removed from 

 the fraction with a cation exchange resin in the hydrogen form and borate removed as 

 volatile methyl borate by repeated distillation with methanol. The separated compounds 

 may then be crystallized from a concentrated solution. In the presence of borate, sugars 

 may also be separated by electrophoretic methods. Sugar mixtures can be separated ac- 

 cording to molecular size using ion exchange resins (23). 



