Chemistry Reference
In-Depth Information
fluid extraction (SFE), and steam distillation. As an example, Vit E can be obtained
from garlic based on extraction. The method requires, first, the homogenization of
garlic in phosphate-buffered saline and then extraction with heptane in the presence
of lithium dodecyl sulfate.
Example 12.1
10 g garlic
1. 400 W microwave for 45 min phosphate-buffered saline
2. Vortex for 30 s (remove
with an equal
)
Add equal volume of ethanol
Vortex for 30 s
Add equal volume of heptane
Vortex for 1 min
Centrifuge for 10 min
3. Remove and evaporation
94 μg α-Tocopherol
The HPLC analysis of α-tocopherol can be achieved using a Bakerbond C-18
column, eluting with a mixture of acetonitrile/methanol/chloroform, 47/47/6.
12.6 VITAMIN B
6
Vit B
6
refers to all 2-methyl-3-hydroxy-5-hydroxy methyl pyridine compounds that
possess the biological activity of pyridoxine. Vit B
6
is a water-soluble and essential
vitamin, and mainly covers four forms of compounds: pyridoxine (PN), pyridoxal
(PA), pyridoxamine (PM), and pyridoxal (PL). They can all be phosphorylated by
pyridoxal kinase to their 5′-phosphates, known as PNP, PLP, and PMP, respectively.
PLP is the metabolically active form, and PNP and PMP can be oxidized to PLP by
PM (PN) 5′-phosphate oxidase. The structures of pyridoxine and its related com-
pounds are shown in
Figure 12.10.
Pyridoxal phosphate (PA) is biologically an important cofactor in many reactions
of amino acid metabolism, including transamination, deamination, and decarboxyl-
ation. PLP, in its metabolically active form, can regulate macronutrient metabolism,
as well as the synthesis and function of the neurotransmitter, histamine, and hemo-
globin, and even gene expression, such as governing the release of glucose from gly-
cogen. Other processes include R-group interconversions; racemization; and alpha-,
beta-, and gamma-elimination. In general, PLP enzymes act through Schiff base
intermediates with the formation of a resonance stabilized carbanion.
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