Alltransretinol

All-trans-retinol, commonly referred to as all-trans-retinol, is the alcohol form of vitamin A. It is a fat-soluble molecule with the chemical formula C20H30O, built around a beta-ionone ring and a long polyene side chain in the all-trans configuration.

Biological role and metabolism: In humans, all-trans-retinol comes mainly from animal-derived foods as retinyl esters and is stored in the liver. It is transported in the bloodstream bound to retinol-binding protein (RBP4) and transthyretin, and taken up by tissues as needed. In the eye, retinol contributes to the visual cycle by being converted to retinaldehyde (retinal), which forms 11-cis-retinal with opsin to regenerate rhodopsin after light exposure. In other tissues, retinol can be oxidized to all-trans-retinoic acid, a potent regulator of gene transcription involved in cell differentiation and development.

Dietary and clinical use: All-trans-retinol supports vision, immune function, and epithelial health. It is used in dietary supplements and, in topical dermatology, ingredients derived from retinol are employed for skin cell turnover and anti-aging effects, typically through gradual conversion to retinoic acid in the skin. In the liver, retinol is stored as retinyl esters and released as needed.

Safety and regulation: As a fat-soluble vitamin, excessive intake can cause hypervitaminosis A, with potential teratogenic effects during pregnancy. Intake is generally guided by established dietary reference values to avoid toxicity while preventing deficiency.

See also: Vitamin A, Retinoic acid, Retinol-binding protein.