70 ALDEHYDES AND ALCOHOLS 



amongst the alcohols belonging to the aromatic series must be 

 mentioned cinnamic alcohol, benzyl alcohol, menthol, borneol, 

 etc. Other monohydric alcohols, with the exception of phyto- 

 sterols and allied substances are of rare occurrence. 



Examples of polyhydric alcohols occurring in plants are 

 mannitol, sorbitol, and dulcitol, isomeric substances of the 

 formula — 



CH.OH CHOH CHOH CHOH CHOH CH^OH 



Mannitol occurs to the extent of about 40-50 per cent in 

 manna, the dried sap of Fraxinus ornus, and up to 20 per cent 

 of the dry weight of Agaricus integer consists of mannitol ; 

 it also occurs in many other fungi and in leaves, twigs and 

 unripe fruits of the olive tree and has been found in 

 Rhinanthus, celery, Syringa vulgaris, asparagus, cauliflower, 

 carrot, pulse, etc. Furthermore, it occurs in various fucoids 

 where it may possibly replace sugars in the metabolism 

 of the plant. Tutin * has shown that apple juice fermented 

 by the bacillus responsible for " cider sickness " results in 

 the reduction of some of the sugar to mannitol. 



Sorbitol occurs in the berries of Pyrus aucuparia and also 

 in apple juice from which it may be obtained by fermenting 

 away the sugars and acetylating the residue with acetic 

 anhydride in the presence of pyridine ; the resulting hexa- 

 acetyl sorbitol is hydrolysed with 2 per cent sulphuric acid and 

 the regenerated sorbitol is crystallized from alcohol. f 



Dulcitol occurs in the cortex of Euonymus europaea and in 

 the bark of Euonymus atropurpurea. It has also been found 

 to occur in Melampyrum arvense and M. pratense. 



It is suggested by Braecke % that the alcohols mannitol and 

 dulcitol are the predominant nutritive compounds for the 

 genera Rhinanthus and Melampyrum respectively, since 

 sucrose is not found at any time as a reserve carbohydrate 

 in Rhinanthus crista galli, Melampyrum pratense or M. arvense. 



Adonitol is a pentahydric alcohol occurring in Adonis 



* Tutin : " Biochem. Joum.," 1925, 19, 418, 



t Tutin : id., 1925, 19, 416. 



% Braecke : " Bull. Soc. Chim. Biol.," 1925, 7, 155. 



