Vitamin A1
Vitamin a, also known as retinol or aquasol a, is a member of the class of compounds known as retinoids. Retinoids are oxygenated derivatives of 3,7-dimethyl-1-(2,6,6-trimethylcyclohex-1-enyl)nona-1,3,5,7-tetraene and derivatives thereof. Thus, vitamin a is considered to be an isoprenoid lipid molecule. Vitamin a is practically insoluble (in water) and an extremely weak acidic compound (based on its pKa). Vitamin a can be found primarily in blood and saliva, as well as throughout most human tissues. Within the cell, vitamin a is primarily located in the cytoplasm and in the membrane (predicted from logP). It can also be found in the extracellular space. Vitamin a exists in all living organisms, ranging from bacteria to humans. In humans, vitamin a is involved in the retinol metabolism. Vitamin a is also involved in vitamin A deficiency, which is a metabolic disorder. Moreover, vitamin a is found to be associated with thyroid cancer and hemodialysis. Vitamin a is a non-carcinogenic (not listed by IARC) potentially toxic compound. Vitamin a is a drug which is used for the treatment of vitamin a deficiency. Vitamin A is a group of unsaturated nutritional organic compounds that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids (most notably beta-carotene). Vitamin A has multiple functions: it is important for growth and development, for the maintenance of the immune system and good vision. Vitamin A is needed by the retina of the eye in the form of retinal, which combines with protein opsin to form rhodopsin, the light-absorbing molecule necessary for both low-light (scotopic vision) and color vision. Vitamin A also functions in a very different role as retinoic acid (an irreversibly oxidized form of retinol), which is an important hormone-like growth factor for epithelial and other cells . Hepatic. Retinol is conjugated with glucuronic acid; the B-glucuronide undergoes enterohepatic circulation and oxidation to retinol and retinoic acid. Retinoic acid undergoes decarboxylation and conjugation with glucuronic acid (DrugBank). Acute toxicity (single ingestion of 7 500 RE or 25 000 IU per kg or more): Signs and symptoms may be delayed for 8 to 24 hours and include: increased intracranial pressure, headache, irritability, drowsiness, dizziness, lethargy, vomiting, diarrhea, bulging of fontanels in infants, diplopia, papilledema. Peeling of skin around mouth may be observed from 1 to several days after ingestion and may spread to the rest of the body (T3DB).