Chemistry Reference
In-Depth Information
13.2.4.
Thiamine Supplementation
For the therapeutic treatment of diseases of the central (CNS) and the
peripheral nervous system (PNS), as well as of exhaustion and during cytostatic
treatment, doses of 50-200 mg thiamine day
-1
are administered orally (Harper,
2006). Clinically manifest beriberi is treated by 50-100 mg day
-1
subcuta-
neously or intravenously for several days, followed by the same dose orally
for several weeks. Besides single cases of anaphylactic shock after intravenous
application, no side effects of higher doses of thiamine (e.g. up to 200 mg day
-1
)
are known (Bitsch, 2002).
13.3.
Riboflavin (Vitamin B2)
The chemical name for riboflavin is 7,8-dimethyl-10-(1
0
-
D
-ribityl)isoalloxa-
zine; riboflavin exists in an oxidized and a reduced form (Figure 13.2) and
from which two co-enzymes are formed, flavin mononucleotide (FMN) and
flavin adenine dinucleotide (FAD; Figure 13.3).
The ending ''flavin'' refers to its yellowish colour (latin ''flavus''
ΒΌ
yellow).
Free, as well as protein-bound riboflavin, occurs in the diet, and milk in
general is the best source. In cow's milk, the free form, with the higher
bioavailability,
is
the
major
one
(61%
riboflavin,
26%
FAD,
11%
5
`
5
'
CH
2
OH
CH
2
OH
HO
HO
OH
Ribitol
OH
HO
HO
CH
2
CH
2
N
H
3
C
N
O
H
3
C
N
N
O
NH
NH
H
N
H
3
C
H
3
C
O
O
7,8-dimethylisoaloxazine
Figure 13.2.
Structures of oxidized (flavoquinone, left) and reduced (flavohydroquinone,
right) forms of riboflavin (vitamin B2).
