38 



CARBOHYDRATES 



CHO 



I 

 HCOH 



I 

 HCOH 



I 

 HOCH 



I 

 HOCH 



I 

 CH3 



6-Desoxy-L-mannose 

 (L-rhamnose) 



They are found in many plant species, particularly in the form of 

 glycosides. These substances show the usual properties of monosaccha- 

 rides, except that on heating with strong acids they yield 5-methyl 

 furfural (contrast aldopentoses, aldohexoses). L-Rhamnose is probably 

 the most abundant of these three sugars in nature. It is' one of the 

 component sugars in several plant gums and mucilages (p. 66) , in the 

 important heart stimulant drugs known as cardiac glycosides, and is 

 present in at least two antibiotics of bacterial origin. These particular 

 antibiotics represent an interesting chemical type because they consist 

 of the sugar, L-rhamnose, attached to a fatty acid, beta hydroxy decanoic 

 acid. 



Vronic acids 



Those simple sugar derivatives which have both an aldehyde and a 

 carboxyl group are termed uronic acids. Three occur in nature, all re- 

 lated to aldohexoses: 



D-Glucuronic acid is found in the animal body as a component of 

 mucopolysaccharides (p. 67) such as heparin and chondroitin. It is 

 utilized by the body to detoxify various harmful drugs which may be 

 ingested. For example, if dogs are fed borneol, it is excreted in the 



