Cyclohexane-1,2,3,4,5,6-hexol is the systematic IUPAC name for the organic compound commonly known as inositol. It denotes a cyclohexane ring bearing a hydroxyl (‑OH) group on each of the six carbon atoms. The molecular formula is C₆H₁₂O₆, and the compound belongs to the class of cyclitols.
Structural Characteristics
- Core: Saturated cyclohexane ring.
- Substituents: Six hydroxyl groups, one on each carbon atom.
- Stereochemistry: Six chiral centers give rise to nine possible stereoisomers. The most abundant naturally occurring isomer is myo‑inositol, in which the hydroxyl groups assume a specific axial/equatorial arrangement that minimizes steric strain.
Physical Properties
| Property | Value |
|---|---|
| Appearance | White crystalline powder |
| Melting point | 168 °C (myo‑inositol) |
| Solubility | Highly soluble in water; limited solubility in ethanol |
| Density | 1.56 g cm⁻³ (myo‑inositol) |
| Optical activity | Optically active; specific rotation varies among isomers |
Natural Occurrence
- Cellular component: Inositol is a ubiquitous constituent of eukaryotic cell membranes, often present as phosphatidylinositol and its phosphorylated derivatives, which play critical roles in signal transduction.
- Biological sources: It is found in high concentrations in plant seeds, fruits, beans, nuts, and whole grains. Human tissues also contain measurable levels, with the highest concentrations in the brain, liver, and kidneys.
Biological Functions
- Second messenger systems: Phosphatidylinositol 4,5-bisphosphate (PIP₂) can be cleaved by phospholipase C to generate inositol 1,4,5‑trisphosphate (IP₃), a key intracellular calcium‑mobilizing messenger.
- Osmoregulation: Inositol acts as an organic osmolyte, helping cells maintain volume under osmotic stress.
- Lipid synthesis: Serves as a structural component of phosphatidylinositol, influencing membrane curvature and trafficking.
Synthesis and Production
- Industrial: Commercial production typically involves hydrogenation of glucose or sucrose derivatives, followed by cyclization and selective hydroxylation steps.
- Biological: De novo biosynthesis in organisms proceeds from glucose-6-phosphate through a series of enzymatic steps, culminating in the formation of myo‑inositol via inositol‑3‑phosphate synthase and inositol monophosphatase.
Applications
- Nutritional supplement: Used as a dietary supplement for its purported benefits in mood regulation, insulin sensitivity, and lipid metabolism, though clinical efficacy varies.
- Pharmaceuticals: Inositol derivatives are employed in the formulation of certain eye drops (e.g., as a component of phospholipid vesicles) and in research on psychiatric disorders.
- Industrial: Serves as a building block for the synthesis of surfactants, polymers, and specialty chemicals.
Safety and Toxicology
- Acute toxicity: Low; the LD₅₀ in rats is > 5 g kg⁻¹ (oral).
- Adverse effects: High oral doses may cause gastrointestinal upset. No significant toxicity has been reported at typical supplemental dosages.
References (Encyclopedic Sources)
- Wikipedia contributors. “Inositol.” Wikipedia, The Free Encyclopedia. Accessed 2026.
- IUPAC. “Compendium of Chemical Terminology (Gold Book).” Inositol entry.
- National Center for Biotechnology Information (NCBI) PubChem Compound Summary for CID 892.
All information presented reflects current scientific consensus as of the knowledge cutoff date (2024‑06) and is derived from established encyclopedic references.
