25(OH)-Vitamin D3/D2 Reversed Phase, HPLC

D vitamins and calciferols arise from provitamins by the splitting of the B-ring of the
steran backbone catalysed by UV radiation of sunlight. The two most important D
vitamins are vitamin D3
and vitamin D2
. In the contrary to vitamin D2
which has to be
added via food, vitamin D3
can be produced in the liver.
Vitamin D3
,formed in the skin or ingested together with vitamin D2
in food, is bound
to a vitamin D binding protein in the plasma, transported into the liver and hydroxylated
in position 25 to form 25-OH-D. More than 95% of 25-OH-D is 25-OH-D3
. 25-OHD2
is only detectable in patients with vitamin D2
medication.