ImageFile = 7-Dehydrochlolesterol.png
Section1 = Chembox Identifiers
CASNo = 434-16-2
PubChem = 172
MeSHName = 7-dehydrocholesterol
Section2 = Chembox Properties
Formula = C27H44O
MolarMass = 384.638
Section3 = Chembox Hazards
Autoignition = 7-Dehydrocholesterol is a
zoosterolthat functions in the serum as a cholesterolprecursor, and is converted to pre-vitamin D3 in the skin, therefore functioning as provitamin-D3. The presence of this compound in human skin enables humans to manufacture vitamin D3 from ultra-violet rays in the sun light, via an intermediate isomerpre-vitamin D3. It is also found in the milkof several mammalian species. ["7-dehydrocholesterol." The American Heritage Stedman's Medical Dictionary. Houghton Mifflin Company, 2002. 21 Jan. 2007. [http://www.answers.com/topic/7-dehydrocholesterol Answers.com] .] It was discovered by Nobel-laureate organic chemist Adolf Windaus.
The skin consists of two primary layers: the inner layer called the
dermis, composed largely of connective tissue, and the outer thinner epidermis. The thickness of the epidermis ranges from 0.08mm to more than 0.6mm (0.003 to 0.024 inches). [ Frediric Martini et al. (2006). Human Anatomy. Pearson/Benjamin-Cummings Publishers, p. 89. ISBN:0-8053-7211-3.] The epidermis consists of five "strata"; from outer to inner they are: the stratum corneum, stratum lucidum, stratum granulosum, stratum spinosum, and stratum basale. The highest concentrations of 7-dehydrocholesterol are found in the epidermal layer of skin, specifically in the stratum basale and stratum spinosum. Norman, Anthony W. (1998) [http://www.ajcn.org/cgi/reprint/67/6/1108.pdf Sunlight, season, skin pigmentation, vitamin D, and 25-hydroxyvitamin D:integral components of the vitamin D endocrine system.] Am J Clin Nutr;67:1108–10.] The production of pre-vitamin D3 is therefore greatest in these two layers, whereas production in the other layers is reduced.
Synthesis of pre-vitamin D3 in the skin involves
UVB radiationwhich effectively penetrates only the epidermal layers of skin. 7-Dehydrocholesterol absorbs UV light most effectively at wavelengths between 270–290 nm and thus the production of vitamin D3 will only occur at those wavelengths. The two most important factors that govern the generation of pre-vitamin D3 are the quantity (intensity) and quality (appropriate wavelength) of the UVB irradiation reaching the 7-dehydrocholesterol deep in the stratum basale and stratum spinosum. Another important consideration is the quantity of 7-dehydrocholesterol present in the skin. Under normal circumstances, ample quantities of 7-dehydrocholesterol (about 25–50 mg/cm2 of skin) are available in the stratum spinosum and stratum basale of human skin to meet the body's vitamin D requirements.
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dehydrocholesterol — dē|hīdrō+ noun Etymology: dehydr + cholesterol : a crystalline steroid alcohol C27H43OH that occurs chiefly in higher animals and man (as in the skin), that is made synthetically from cholesterol, and that yields vitamin D3 on irradiation with… … Useful english dictionary
dehydrocholesterol — noun A sterol, found in the skin, that, on exposure to light, is converted into vitamin D … Wiktionary
dehydrocholesterol — [di:ˌhʌɪdrə(ʊ)kə lɛstərɒl] noun Biochemistry a compound present in the skin, which is converted to cholecalciferol (vitamin D3) by ultraviolet light. Origin 1930s: from dehydro that has lost hydrogen + cholesterol … English new terms dictionary
dehydrocholesterol — de·hy·dro·cholesterol … English syllables
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