Provitamin D3 (7-dehydrocholesterol)

Description 7-dehydrocholesterol

Pharmacological group: provitamins
Molecular Formula C27H44O
Molar mass 384.638
7-dehydrocholesterol - zoosterols is operable in serum cholesterol as precursors in the skin and converted to vitamin D3, therefore, it acts as a pro-vitamin D3. The presence of this compound in the skin allows a person to produce vitamin D3 from the ultraviolet rays of sunlight through the intermediate isomer provitamin D3. It is also found in the milk of several species of mammals. In insects, it is a precursor of the hormone ecdysone required for their maturation. It was first discovered by Nobel laureate organic chemist Adolf Windaus.

Provitamin D3 in humans
Skin is composed of two main layers: the inner layer called the dermis, which consists primarily of connective tissue and an outer thin epidermis. The thickness of the epidermis is between 0.08 mm to 0.6 mm (0.003 to 0.024 inches). The epidermis consists of five layers: the stratum corneum, the transparent layer, the granular layer, basal layer and papillary layer, in order from outside to inside. The highest concentration of 7-dehydrocholesterol are in the epidermal layer of the skin, particularly the basal and papillary layers.

Solar radiation and synthesis of provitamin D3
Synthesis of provitamin D3 in the skin occurs by UV radiation, which effectively penetrates only through the epidermal layer of the skin. 7-dehydrocholesterol most effectively absorbs ultraviolet light at wavelengths between 290 and 320 nm, thus, production of vitamin D3 occurs only at these wavelengths. The two most important factors that control the generation of pro-vitamin D3 - is the amount (intensity) and quality (appropriate wavelength) UV radiation. Another important factor - the number of 7-dehydrocholesterol in the skin. Under normal conditions, the basal and in the papillary layers of human skin is a sufficient amount of 7-dehydrocholesterol (about 25-50 mg / cm2 skin).