A provitamin is a substance that may be converted within the body to a
vitamin
Vitamins are Organic compound, organic molecules (or a set of closely related molecules called vitamer, vitamers) that are essential to an organism in small quantities for proper metabolism, metabolic function. Nutrient#Essential nutrients, ...
.
The term previtamin is a synonym.
The term "provitamin" is used when it is desirable to label a substance with little or no vitamin activity, but which can be converted to an active form by normal
metabolic
Metabolism (, from ''metabolē'', "change") is the set of life-sustaining chemical reactions in organisms. The three main functions of metabolism are: the conversion of the energy in food to energy available to run cellular processes; the ...
processes.
Example
Some provitamins are:
* "Provitamin A" is a name for
β-carotene,
[ which has only about 1/6 the ]biological activity
In pharmacology, biological activity or pharmacological activity describes the beneficial or adverse effects of a drug on living matter. When a drug is a complex chemical mixture, this activity is exerted by the substance's active ingredient or ...
of retinol
Retinol, also called vitamin A1, is a fat-soluble vitamin in the vitamin A family that is found in food and used as a dietary supplement. Retinol or other forms of vitamin A are needed for vision, cellular development, maintenance of skin and ...
(vitamin A
Vitamin A is a fat-soluble vitamin that is an essential nutrient. The term "vitamin A" encompasses a group of chemically related organic compounds that includes retinol, retinyl esters, and several provitamin (precursor) carotenoids, most not ...
); the body uses an enzyme
An enzyme () is a protein that acts as a biological catalyst by accelerating chemical reactions. The molecules upon which enzymes may act are called substrate (chemistry), substrates, and the enzyme converts the substrates into different mol ...
to convert β-carotene to retinol. In other contexts, both β-carotene and retinol are simply considered to be different forms ( vitamers) of vitamin A.
* "Provitamin B5" is a name for panthenol
Panthenol (also called pantothenol) is the alcohol analog of pantothenic acid (vitamin B5), and is thus a provitamin of B5. In organisms, it is quickly oxidized to pantothenic acid. It is a viscous transparent liquid at room temperature. Panth ...
, which may be converted in the body to vitamin B5 (pantothenic acid
Pantothenic acid (vitamin B5) is a B vitamin and an essential nutrient. All animals need pantothenic acid in order to synthesize coenzyme A (CoA), which is essential for cellular energy production and for the synthesis and degradation of prote ...
).
* Menadione
Menadione is a natural organic compound with the formula C6H4(CO)2C2H(CH3). It is an analog of 1,4-naphthoquinone with a methyl group in the 2-position. It is sometimes called vitamin K3. Use is allowed as a nutritional supplement in animal ...
is a synthetic provitamin of vitamin K
Vitamin K is a family of structurally similar, fat-soluble vitamers found in foods and marketed as dietary supplements. The human body requires vitamin K for post-translational modification, post-synthesis modification of certain proteins ...
.
* Provitamin D2 is ergosterol
Ergosterol (ergosta-5,7,22-trien-3β-ol) is a mycosterol found in cell membranes of fungi and protozoa, serving many of the same functions that cholesterol serves in animal cells. Because many fungi and protozoa cannot survive without ergostero ...
, and provitamin D3 is 7-dehydrocholesterol. They are converted by UV light into vitamin D.[ The human body produces provitamin D3 naturally; deficiency is usually caused by a lack of sun exposure, not a lack of the provitamin.]
References
Vitamins
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