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Cholecalciferol
IUPAC name	(3β,5Z,7E)-9,10-secocholesta- 5,7,10(19)-trien-3-ol
Other names	vitamin D3, activated 7-dehydrocholesterol.
Identifiers
CAS number	67-97-0
EC number	200-673-2
SMILES	O[C@@H]1CC(\C(=C)CC1)=C\C=C2/CCC[C@]3(C2CC[C@@H]3[C@H](C)CCCC(C)C)C
InChI	1/C27H44O/c1-19(2)8-6-9-21(4)25-15-16-26-22(10-7-17-27(25,26)5)12-13-23-18-24(28)14-11-20(23)3/h12-13,19,21,24-26,28H,3,6-11,14-18H2,1-2,4-5H3/b22-12+,23-13-/t21-,24+,25-,26?,27-/m1/s1
InChI key	QYSXJUFSXHHAJI-QWSSABAFBD
ChemSpider ID	9058792
Properties
Molecular formula	C27H44O
Molar mass	384.64 g/mol
Appearance	White, needle-like crystals
Melting point	83–86 °C
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Cholecalciferol is a form of Vitamin D, also called vitamin D₃ or calciol.^[1]

It is structurally similar to steroids such as testosterone, cholesterol, and cortisol (though vitamin D₃ itself is a secosteroid).

One gram of pure vitamin D₃ is 40 000 000 (40x10⁶) IU, or, in other words, one IU is 0.025 μg. Individuals having a high risk of deficiency should consume 125 μg (5000 IU) of vitamin D daily.^{[citation needed]}

[edit] Forms

Vitamin D₃ has several forms:

• Cholecalciferol, (sometimes called calciol) which is an inactive, unhydroxylated form of vitamin D₃)
• Calcifediol (also called 25-hydroxyvitamin D₃), which is the form measured in the blood to assess vitamin D status
• Calcitriol (also called 1,25-dihydroxyvitamin D₃), which is the active form of D₃.

[edit] Metabolism

7-Dehydrocholesterol is the precursor of vitamin D₃ and forms cholecalciferol only after being exposed to solar UV radiation.

Cholecalciferol is then hydroxylated in the liver to become calcifediol (25-hydroxyvitamin D₃).

Next, calcifediol is again hydroxylated, this time in the kidney, and becomes calcitriol (1,25-dihydroxyvitamin D₃). Calcitriol is the most active hormone form of vitamin D₃.

[edit] Regulation of metabolism

• Cholecalciferol is synthesized in the skin from 7-dehydrocholesterol under the action of ultraviolet B light. It reaches an equilibrium after several minutes depending on several factors including conditions of sunlight (latitude, season, cloud cover, altitude), age of skin, and color of skin.
• Hydroxylation in the liver of cholecalciferol to calcifediol (25-hydroxycholecalciferol) is loosely regulated, if at all, and blood levels of this molecule largely reflect the amount of vitamin D₃ produced in the skin or the vitamin D₂ or D₃ ingested.
• Hydroxylation in the kidneys of calcifediol to calcitriol by 1-alpha-hydroxylase is tightly regulated (stimulated by either parathyroid hormone or hypophosphatemia) and serves as the major control point in production of the most active circulating hormone calcitriol (1,25-dihydroxyvitamin D₃).

[edit] As food fortification

Although cholecalciferol can be synthesized in the skin (see Metabolism), it is also a form of vitamin D added to fortify foods. Cholecalciferol is produced industrially by the irradiation of 7-dehydrocholesterol extracted from lanolin found in sheep's wool. In foods where animal products are not desired, an alternative compound is ergocalciferol (also known as vitamin D₂) derived from the fungal sterol ergosterol.

[edit] Dose

There are conflicting reports concerning the absorption of cholecalciferol (D₃) versus ergocalciferol (D₂), with some studies suggesting less efficacy of D₂^[2], and others showing no difference^{[2] [3]}. At present, D₂ and D₃ doses are frequently considered interchangeable, but more research is needed to clarify this.

[edit] Stability

Cholecalciferol is very sensitive to UV radiation and will rapidly, but reversibly, break down to form supra-sterols, which can further irreversibly convert to ergosterol.

[edit] Therapeutic Application

A 2008 study published in Cancer Research has shown the addition of vitamin D₃ (along with calcium) to the diet of some mice fed a regimen similar in nutritional content to a new Western diet prevented colon cancer development.^[4]

[edit] Alternative Views

There is a minority view, often associated with Trevor Marshall, which asserts that low levels of calcifediol (25-hydroxyvitamin D3) are often due to overconversion into calcitriol (1,25-dihydroxyvitamin D3, the active form of D3) because of chronic infection rather than calcifediol deficiency. [1]

[edit] See also

• Hypervitaminosis D, Vitamin D poisoning
• Ergocalciferol, vitamin D₂.
• 25-Hydroxyvitamin D3 1-alpha-Hydroxylase, a kidney enzyme that converts calcifediol to calcitriol.

[edit] References

[edit] External links

• NIST Chemistry WebBook page for cholecalciferol
• http://www.VitaminDCouncil.org
• http://www.uctv.tv/search-details.aspx?showID=15751
• http://www.uctv.tv/search-details.aspx?showID=15767

  Adosterol- Cholecalciferol/Ergocalciferols- Cholesterol- Dihydrotachysterol- Fusidic acid- Lanosterol- Phytosterols v • d • e Cholestanes, membrane lipids: sterols

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