7-dehydrocholesterol

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Structural formula
Structure of 7-dehydrocholesterol
General
Surname 7-dehydrocholesterol
other names
  • (3 S , 10 R , 13 R , 17 R ) -10,13-dimethyl-17- (6-methylheptan-2-yl) -2,3,4,9,11,12,14,15,16, 17-decahydro-1 H -cyclopenta [ a ] phenanthren-3-ol
  • Cholesta-5,7-dien-3 β -ol
  • Provitamin D 3
Molecular formula C 27 H 44 O
Brief description

white solid

External identifiers / databases
CAS number 434-16-2
EC number 207-100-5
ECHA InfoCard 100.006.456
PubChem 439423
ChemSpider 388534
Wikidata Q139350
properties
Molar mass 384.34 g mol −1
Physical state

firmly

Melting point

148-152 ° C

safety instructions
GHS labeling of hazardous substances
no GHS pictograms
H and P phrases H: no H-phrases
P: no P-phrases
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

7-Dehydrocholesterol is a sterol which is the precursor to cholesterol and cholecalciferol (vitamin D 3 ). 7-dehydrocholesterol was discovered by the later Nobel Prize winner Adolf Windaus .

place

The skin is made up of two main layers. An inner layer, the dermis , and a thin, outer layer, the epidermis. The thickness of the epidermis is between 0.08 mm and 0.6 mm. The highest concentration of 7-dehydrocholesterol can be found in the epidermal layer, especially in the stratum spinosum and stratum basale . The production of previtamin D 3 is greatest between these two layers.

function

Formation of cholesterol

The enzyme 7-dehydrocholesterol reductase reduces 7-dehydrocholesterol to cholesterol .

In Smith-Lemli-Opitz syndrome, this enzyme is limited in its activity by various mutations. As a result, in this syndrome, the 7-dehydrocholesterol level in the blood is too high and the cholesterol level is too low. Cholesterol in turn serves as the starting substance for steroid hormones and bile acids .

Formation of vitamin D.

7-Dehydrocholesterol is first converted into previtamin D 3 by photolysis with UVB light of wavelengths 270-315 nm and then further converted into vitamin D 3 by thermal isomerization .

radiation

The synthesis of previtamin D 3 leads to the release of UVB radiation , which, however, practically only penetrates the epidermal layers of the skin. 7-Dehydrocholesterol absorbs UV light best between the wavelengths 290 nm and 320 nm, which is why the production of vitamin D 3 must take place between these wavelengths. The two most important factors for the generation of Previtamin D 3 are the quantity (intensity) and the quality (suitable wavelength).

Individual evidence

  1. ↑ a b c d data sheet 7-dehydrocholesterol from Sigma-Aldrich , accessed on June 15, 2011 ( PDF ).
  2. ^ F. Martini, MJ. Timmons: Human Anatomy . Ed .: Pearson / Benjamin-Cummings Publishers. 2006, ISBN 0-8053-7211-3 , pp. 89 .
  3. ↑ AW Norman: Sunlight, season, skin pigmentation, vitamin D, and 25-hydroxyvitamin D: integral components of the vitamin D endocrine system . In: The American Journal of Clinical Nutrition . tape 67 , no. 6 , June 1, 1998, ISSN  0002-9165 , p. 1108–1110 , doi : 10.1093 / ajcn / 67.6.1108 ( oup.com [accessed May 31, 2020]).
  4. ↑ Metabolism of vitamin D ( Memento from March 18, 2016 in the Internet Archive ).
  5. ↑ AW Norman: Sunlight, season, skin pigmentation, vitamin D, and 25-hydroxyvitamin D: integral components of the vitamin D endocrine system . In: The American Journal of Clinical Nutrition . tape 67 , no. 6 , June 1, 1998, ISSN  0002-9165 , p. 1108–1110 , doi : 10.1093 / ajcn / 67.6.1108 ( oup.com [accessed May 31, 2020]).

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