Alcohols are saturated organic compounds that contain at least one hydroxyl group (OH). The general formula of alcohol is CnH2n+1OH. Alcohol can be of many types. In this article, we will discuss the mannitol. This article will cover all important points like what is mannitol, mannitol structure, mannitol uses, mannitol action and mannitol injection uses.
What is Mannitol?
Mannitol is a six-carbon, linear, simple, and polyhydroxy sugar alcohol. It is a low molecular weight compound. Its chemical formula is C6H14O6. It gets easily filtered through the glomerulus but it can not be reabsorbed in the renal tubule of the kidney.
Mannitol Structure
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Mannitol is an isomer of sorbitol. The only difference in the structure of mannitol from sorbitol is the orientation of the hydroxyl group on the second carbon. All the carbons present in the mannitol are sp3 hybridized. All bonds present in the mannitol are sigma bonds.
Comparison of Sorbitol and Mannitol.
Properties of Mannitol
The molar mass of mannitol is 182.172 g/mol.
The density of mannitol is 1.489 at 68°F.
The boiling point of mannitol is 563°F at 3.5 mm Hg.
The melting point of mannitol is 333°F.
It is an odourless compound.
It occurs naturally in white crystalline or in granule form.
It is sweet in taste.
Mannitol Action
Mannitol is a polyhydroxy compound, which is mildly metabolized by the body. The renal tubule does not have the capacity to absorb it. Therefore, it rapidly gets excreted by the kidney, when mannitol injection is used and poorly absorbed when taken orally.
Mannitol, when ingested orally, passes through the intestine and excreted in the feces as the small intestine is not able to absorb it properly. Therefore, it does not affect blood sugar and can be used as a sweetener for the diabetic patient.
Mannitol Uses
Mannitol is used for promoting diuresis for acute renal failure.
Mannitol is used for increased intracranial pressure.
Mannitol is used for the excretion of toxic material.
Mannitol is used as a sweetener for diabetic food products.
Mannitol is used for preventing intradialytic hypotension.
It is used to measure Extracellular Fluid (ECF) and Glomerular Filtration Rate (GFR).
It is used in cardiopulmonary bypass.
Mannitol Injection Uses
Mannitol is used as a medicine. Mannitol infused into a vein or into the urethra. It should never be given subcutaneously. It is infused by health care professionals in a hospital or clinic. The total concentration, dosage, and rate of mannitol administration should be governed by the nature and severity of the condition. The standard adult dose ranges from 50-200 g/day. The rate of infusion is usually adjusted to maintain a urine flow.
Harmful Effects of Mannitol
It can cause dehydration when consumed in excess amounts.
At low temperature, it gets precipitated and can damage the vascular organ system.
It can cause heart failure.
It can cause pulmonary edema.
It can cause renal failure.
Did You Know?
Mannitol is found in mushrooms, brown algae, and bark of manna trees.
Mannitol lowers the blood pressure.
Mannitol in the intestine for a long time can cause bloating and diarrhoea.
FAQs on Mannitol
1. What is Mannitol and where is it found in nature?
Mannitol is a type of sugar alcohol (or polyol), which is an organic compound derived from a sugar. It is naturally found in a variety of plants and algae. Its most significant biological role is as a storage carbohydrate in brown algae (Phaeophyceae), such as kelp. It is also present in smaller amounts in fungi, lichens, and the exudates of several trees like the manna ash.
2. What are the key physical and chemical properties of Mannitol?
Mannitol exhibits several distinct properties that are important for its applications. The main properties are:
Appearance: It is a white, odourless, crystalline powder or granule.
Solubility: It is soluble in water and slightly soluble in alcohol.
Taste: It has a sweet taste, approximately 50-60% as sweet as sucrose, with a cooling sensation in the mouth.
Melting Point: It has a relatively high melting point, typically between 166-168°C (331-334°F).
Isomerism: It is an isomer of sorbitol, another common sugar alcohol.
3. What is the biological significance of Mannitol in the Plant Kingdom?
In the Plant Kingdom, Mannitol's primary role is as a form of energy storage. Specifically, for the class Phaeophyceae (brown algae), food is stored as complex carbohydrates in the form of laminarin and mannitol. This stored energy is used by the algae to fuel metabolic processes, similar to how starch functions in higher plants or glycogen in animals.
4. How is Mannitol different from Sorbitol?
While both Mannitol and Sorbitol are isomers with the same chemical formula (C₆H₁₄O₆), their structures differ. The key distinction lies in the spatial orientation of the hydroxyl (-OH) group on the second carbon atom (C-2). This structural difference, known as stereoisomerism, leads to different physical properties such as melting point, solubility, and how they crystallise. This is a common concept among sugar alcohols.
5. How does Mannitol function as an osmotic diuretic?
Mannitol acts as an osmotic diuretic by increasing the solute concentration (osmolarity) of the filtrate within the kidney tubules. When administered intravenously, it is freely filtered by the glomerulus but is poorly reabsorbed by the renal tubules. This high concentration of mannitol in the filtrate draws water from the surrounding tissues into the tubules via osmosis, preventing water reabsorption and thereby increasing urine output. This makes it a useful diuretic in specific medical situations.
6. Why is a Mannitol solution considered hypertonic in medical applications?
A solution is described as hypertonic when it has a higher concentration of solutes compared to another solution across a semipermeable membrane. In a medical context, an intravenous Mannitol solution is hypertonic relative to the body's cells and blood plasma. This property is crucial for its therapeutic effect, as the higher osmotic pressure of the mannitol in the blood pulls excess fluid from body tissues (like the brain, to reduce intracranial pressure) into the bloodstream, which is then filtered and expelled by the kidneys.
7. What are the common applications of Mannitol outside of its direct medical use?
Besides its use as a diuretic, Mannitol has several other important applications:
Food Industry: It is used as a sugar substitute in foods for people with diabetes because it is poorly absorbed from the intestines, causing a minimal impact on blood sugar levels.
Pharmaceuticals: It serves as an excipient, or inactive ingredient, in drug formulations. It can be used as a diluent or binder in tablet medicine.
Research: In microbiology, it is a key component of Mannitol Salt Agar (MSA), a selective medium used to grow certain types of bacteria.
