Selected Vitamins - Natural Products Chemistry: Sources, Separations, and Structures - page 130

12.3 ISOLATION OF VITAMIN C
Many methods are known to obtain Vit C. One process to extract Vit C from lemon
juice is shown next. The choice of isolation steps can take advantage of the acidic
groups present in the molecule. A cation exchange column is first used as a “filter”
and for the final separation step an anion exchange column is used.

Juice from Lemon

Filter through AG50-WX4 cation resin

Adjust pH
Apply to AG 1-X8 anion exchange resin

Elute dilute HCl

12.4 VITAMIN D
Vit D (Figure 12.5) is not an essential dietary vitamin, as it is synthesized in the
body when exposed to sunlight. Vit D was discovered in an effort to understand the
cause of rickets, especially in children. Rickets is characterized by impeded growth;
and soft, weak, deformity of the bones leading to bow legs as a result of calcium/
phosphorus deficiency, as well as a lack of Vit D. Today, Vit D is added to staple
foods, such as milk, to avoid this disease due to any nutrient deficiency. Furthermore,
the combination of Vit D together with calcium is generally believed to be important
for bone health.
The metabolism of Vit D in the body is shown in Figure 12.6. In the liver, Vit D 3
is converted to 25-hydroxyvitamin D 3, (25(OH)D 3 ). Vit D 2 is converted in the liver to
25-hydroxyergocalciferol, also known as 25-hydroxyvitamin D 2 , (25(OH)D 2 ), shown

H

HO

FIGURE 12.5 Chemical structure of vitamin D3.