190 PHYSIOLOGY OF NUTRITION 



of cane sugar is there any transformation of the latter into starch; Bohm 

 obtained quite analogous results by artificially supplying sugar to the plant. 



§10. Glucosides. "■ — Glucosides 1 are chemical combinations of glucose (some- 

 times of other sugars) with various other substances, and they are split into their 

 component parts by the action of acids or glucoside-splitting enzymes. For 

 example, under the influence of emulsin, arbutin takes up water and produces 

 hydroquinone and glucose. This reaction is shown below:"' 



-o- - 



CH 2 OH— CHOH— CH— CHOH— CHOH— CH—OC 6 H 4 OH (arbutin) + 



-o- _ 



H 2 (water) = CH 2 OH— CHOH— CH— CHOH— CHOH— CHOH (glucose) + 

 HOC 6 H 4 OH (hydroquinone). 



Indican, a glucoside of the indigo plant, etc., forms glucose and indoxyl, 

 with the taking up of water: 



C 7 H 6 NC— 0— C 6 H„0 5 (indican) + H 2 (water = 



COH 

 C 6 H 12 6 (glucose) + C 6 H/ ^CH (indoxyl). 



X NH' 



Indoxyl oxidizes in the air, forming dark blue indigotin (indigo blue) and water: 



2 C 8 H 7 ON + Oo = 2 H 2 + C 16 H 10 O 2 N 2 . 

 Indigotin has the structural formula, 



/ co \ _ / co \ 



C6-H.4x /C — Cv /C6H4. 



X NH' X NH X 



As a third example may be mentioned amygdalin, an a-(3 glucoside of almond, 

 peach, etc., which takes up water and splits into glucose, benzaldehyde and 

 hydrocyanic acid: 



1 -o- 



CH 2 OH— CHOH— CH— CHOH— CHOH— CH— O— CH 2 — CHOH- 



C6H5 



CH— CHOH— CHOH— CH—O—CH (amygdalin) + H 2 (water) = 2C 6 H 12 6 



L -0 [ I 



CN 

 (glucose) + CeH 5 — CHO (benzaldehyde) -f HCN (hydrocyanic acid). 



Glucosides may undergo autolysis in the tissues. Thus, if leaves of Polygo- 

 num tinctorium are exposed to an atmosphere saturated with chloroform 

 vapor (which kills the cells), blue indigotin is formed in the tissues. The chlor- 



1 Rijn, van, 1900. (See note 3, p. 184.] 



" This section appears for the first time in the 7th Russian edition. — Ed. 



w For this and similar statements of formulas and reactions, see Haas and Hill, 1013. [See 

 note 3, p. 6.) Also see works on organic chemistry; an excellent short treatise for physio- 

 logical students is Bernthsen, A., A text-book of organic chemistry. Translated and edited 

 by J. J. Sudborough. New York. 1907. — Ed. 



