The gonane skeleton, with the IUPAC recommended numbering of the carbon atoms
Vitamin D2 supplements

In human nutrition, ergosterol is a provitamin form of vitamin D2; exposure to ultraviolet (UV) light causes a chemical reaction that produces vitamin D2.

- Ergosterol

Ergocalciferol is a secosteroid formed by a photochemical bond breaking of a steroid, specifically, by the action of ultraviolet light (UV-B or UV-C) on ergosterol, a form of provitamin D2.

- Ergocalciferol
The gonane skeleton, with the IUPAC recommended numbering of the carbon atoms

1 related topic

Alpha

Cholecalciferol (D3)

Vitamin D

Group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects.

Group of fat-soluble secosteroids responsible for increasing intestinal absorption of calcium, magnesium, and phosphate, and many other biological effects.

Cholecalciferol (D3)
Calcium regulation in the human body. The role of active vitamin D (1,25-dihydroxyvitamin D, calcitriol) is shown in orange.
Global vitamin D serum levels among adults (nmol/L).
The photochemistry of vitamin D biosynthesis in animal and fungi
Thermal isomerization of previtaminD3 to vitamin D3
In the epidermal strata of the skin, vitamin D production is greatest in the stratum basale (colored red in the illustration) and stratum spinosum (colored light brown).
Liver hydroxylation of cholecalciferol to calcifediol
Kidney hydroxylation of calcifediol to calcitriol

In humans, the most important compounds in this group are vitamin D3 (also known as cholecalciferol) and vitamin D2 (ergocalciferol).

Vitamin D2 is found in fungi and is produced by ultraviolet irradiation of ergosterol.