Chemistry Reference
In-Depth Information
12.3.
Vitamin D
12.3.1.
Chemistry and Analysis
The term 'vitamin D' was given during the early 1920s to a group of
closely related secosteroids with antirachitic properties. The two major diet-
ary forms of vitamin D in foods are chole-calciferol (vitamin D
3
, derived from
animals) and ergo-calciferol (vitamin D
2
, derived from plants) (Figure 12.2).
Both chole- and ergo-calciferol are also formed by photoirradiation from
their precursors 7-dehydrocholesterol and ergosterol in vetebrates and some
fungi, respectively. The chemical structures of vitamin D
2
and vitamin D
3
differ only in their side chain at C-17 which in vitamin D
2
has a double bond
and an additional methyl group.
Ergocalciferol (Vitamin D
2
)
Cholecalciferol (Vitamin D
3
)
25-hydroxyvitamin D
3
(Calcidiol)
1,25-dihydroxyvitamin D
3
(Calcitriol)
Figure 12.2.
Structures of the major metabolites of vitamin D.
