Mannitol and Anhydrides

D-Mannitol, mannite or manna sugar is the name applied to this hexahydric alcohol widely distributed throughout the vegetable kingdom. It comprises as much as 75% of the medicinal saccharin exudation known as manna, Fraxinus ornus. The compound was isolated first by Proust in 1806. The early metabolic studies on mannitol were carried out with the naturally occurring alcohol in manna, which is n-mannitol. 

In 1883 Jaffe showed that D-mannitol could be fed to dogs and recovered unchanged in large quantities from the urine. In rabbits the compound was partially metabolized. Sollmann suggests the use of mannitol as a sweetening agent in the diabetic diet. In 1919 Field  

Silberman and Lewis in 1933 published data contrary to the findings of the former investigators to indicate that mannitol behaved as an inert substance in the metabolic pattern of the white rat and was incapable of serving as a precursor of glycogen. They administered the mannitol by stomach tube. Later, Carr and Krantz confirmed the work of Silberman and Lewis, showing that when mannitol is fed over comparatively long 

Todd and coworkers showed that mannitol did not elevate the blood-sugar level of dogs upon intravenous injection, but its isomer, sorbitol, served as a precursor of glucose under the same conditions. Smith and coworkers found that upon intravenous injection of mannitol in man, 85 percent of the sugar alcohol was recoverable unchanged from the urine. 

Ellis and Krantz, using Macacus rhesus monkeys, administered 8 g. of mannitol per kilo of body weight by stomach-tube. Three hours later the animals were anesthetized with sodium pentobarbital and two or three portions of the liver were taken from different lobes of each animal for individual glycogen determinations. In four animals used as controls, the mean liver-glycogen value was 0.28 percent with mannitol, in six animals, the value was 0.53 percent. This is not a definitely significant increase considering the wide variations in the control values. Sorbitol under the same conditions gave a mean value of 0.72 percent. 

To summarize, the fate of mannitol in the animal body appears to proceed along the following pattern absorption from the alimentary tract partial conversion to glycogen in the liver and the elimination of much of the sugar alcohol unchanged in the urine. 

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