Retinol

• Retinol
• Axerophthol

A11CA01, D10AD02, R01AX02, S01XA02

61-63 ° C

120-125 ° C

Attention

Retinol, vitamin A1 or axerophthol, is a fat soluble neckband vitamin. Chemically heard retinol to the diterpenoids and is a monovalent, primary alcohol. The ring contained six carbon atoms is called β - Jononring, and the molecule also has a number of conjugated double bonds, which are crucial for its participation in the visual process.

Often retinol, is also in many textbooks, simplistically equated with vitamin A. However, it is understood from vitamin A rather a group of substances of β - Jononderivaten that have the same biological activity spectrum as all-trans- retinol, excluding the pro-vitamins A.

History

Retinol was discovered in 1913 by Elmer McCollum and Marguerite Davis ( 1887-1967 ). It is described as a fat-soluble vitamin, and its significance as a factor antixerophthalmatischen. Until 20 years later the purification of retinol from liver by Paul Karrer.

The first total synthesis of retinol succeeded 1947 to the Dutch chemists Jozef Ferdinand Arens ( 1914-2001 ) and David Adriaan van Dorp ( 1915-1995 ) by stepwise reduction of tretinoin. According to them, this synthesis Arens- van Dorp synthesis was called.

Occurrence

Natural Retinolquellen are fish, liver products, butter, egg yolks and dairy products.

Metabolism

The vitamin A metabolism is controlled primarily by so-called RBPs (retinol - binding proteins ). Only with the help of vitamin A is used for the body, causing a deficiency of these proteins can lead to symptoms similar to a vitamin A deficiency ( hypovitaminosis ) itself

Can not be bound by RBPs excess retinol, as occurs poisoning. They therefore play a crucial role in hypervitaminosis A. Since they have a so-called zinc finger, the trace element zinc is important for the entire vitamin A household - both under-and over-supply.

Reactions

The synthesis of vitamin A - active compounds is based on a retinol ester (mostly vitamin A palmitate ), of:

Demand

Humans need vitamin A1 (retinol ), but can also make use of provitamin A ( β -carotene). Since the provitamin is not equally utilisierbar (absorption, conversion ) is required to be higher. Grob is specified by the German Nutrition Society ( DGE), the need for the adult as follows:

• 2 mg of β -carotene

• 0.5 mg Vitamin A and 1 mg of β -carotene.

The cat also requires retinol or vitamin A1, but occupies a special position, in contrast to almost all other animals because they can not convert β -carotene to retinol and therefore naturally can supply sufficient only by eating liver with vitamin A.

Synthesis

A key step in the industrial production of Vitamin A is the Wittig reaction. For these widely applicable Georg Wittig reaction was awarded the Nobel Prize for Chemistry in 1979.

In the first part of the synthesis is made by a dehydrolinalool of C15 salt. This responds by Wittig reaction with a C5 - acetate, which is prepared from dimethoxyacetone, for retinol. This can be changed to several other steps in the retinol.

1 RE (retinol equivalent) = 1 microgram of retinol = 6 micrograms of β -carotene