MOLECULE

Mannitol

Mannitol, also known ashexan-1,2,3,4,5,6-hexol (C6H8(OH)6), osmitrol or tobrex, belongs to the class of organic compounds known as sugar alcohols. These are hydrogenated forms of sugars in which the carbonyl group (aldehyde or ketone of the reducing sugar) has been reduced to a primary or secondary hydroxyl group. Mannitol is one of the most abundant energy and carbon storage molecules in nature, and is produced by a plethora of organisms, including bacteria, fungi, algae, lichens, and many plants such as Cannabis (PMID:19578847). Mannitol is commonly used as a sweetener in diabetic foods as it is poorly absorbed by the intestines. Mannitol is also used as medication to decrease pressure in the eyes, (i.e. glaucoma) and to lower increased intracranial pressure. Mannitol is an osmotic diuretic agent and a weak renal vasodilator. It has little significant energy value as it is largely eliminated from the body before any metabolism can take place. Mannitol can be used to treat oliguria associated with kidney failure or other manifestations of inadequate renal function. Mannitol is commonly used as a research tool in cell biological studies, usually to control osmolarity. Chemically, mannitol as a sugar alcohol, is similar to xylitol or sorbitol and is considered an isomer of sorbitol. However, mannitol has a tendency to lose a hydrogen ion in aqueous solutions, which causes the solution to become acidic. For this reason, it is not uncommon to add a base to adjust its pH, such as sodium bicarbonate. Mannitol is a non-permeating molecule, meaning that it cannot cross biological membranes. Because of this inability to cross biological membranes, mannitol has been used for the determination of glomerular filtration rate (GFR). Altered levels of mannitol have been found to be associated with cytochrome c oxidase deficiency and ribose-5-phosphate isomerase deficiency, which are inborn errors of metabolism. Mannitol is also a microbial metabolite found in Aspergillus, Candida, Clostridium, Gluconobacter, Lactobacillus, Lactococcus, Leuconostoc, Pseudomonas, Rhodobacteraceae, Saccharomyces, Streptococcus, Torulaspora and Zymomonas (PMID: 15240312; PMID: 29480337).