THE CARBOHYDRATES 



203 



CHITIN AND CHONDROITIN. 



These polysaccharides which contain glucosamine as monosaccharide unit 

 appear to be tetrasaccharides. 



Chitin. 



Chitin is composed of four glucosamine units or of three glucosamine 

 units and one glucose unit, the amino groups of the glucosamine being acety- 

 lated. It has been represented as having the formula 



Cm CHOH-CH-CHOH-CHNHCOCHs-CH 



CH-CHNHCOCH3-CHOH-CH-CHOH-CH 2 



CHOH-CH-CHOH-CH 2 



CH 9 -CHOH-CH CHOH-CHNHCOCH 3 -CH 



tout this formula requires confirmation. 



Chitin is prepared from the shells of lobsters or crabs ; they are freed from 

 meat, etc., mechanically, or by treatment with dilute sodium hydroxide and 

 washing with water, dried and powdered. The powder is treated with dilute 

 hydrochloric acid, water, boiling alcohol, water, boiling alcohol and ether. 



The powder as obtained above is colourless ; if the whole of small animals 

 such as cockchafers be used the chitin consists of the skeletal, structure of the 

 animal. It is insoluble in water and other solvents, but is decomposed by 

 concentrated hydrochloric acid yielding glucosamine hydrochloride (p. 189) and 

 acetic acid. Three or four molecules of acetic acid are given by chitin. 



Chondroitin. 



Chondroitin or chondroitin sulphuric acid, is contained in cartilage 

 either as such or in combination with protein, as a glucoprotein, i.e. as a 

 chondroprotein. The work of Levene and La Forge l shows that it is a 

 tetrasaccharide consisting of two chondrosamine units and two glycuronic 

 acid units, the amino groups of the chondrosamine units being acetylated 

 and its primary alcohol groups esterified with sulphuric acid. They gave it 

 the formula : 



OH 



HO'SCyOCH, d- 

 H 



/ H QH S 



CH, HOOC-0 C 

 00 / H OH H 



H NH H 



C C 6 O 



.OH H 



H 



1 J. Biol. Chem., 1913, 15, 69, 155. 



