Vitamin C (IDK® Vitamin C) (Ascorbic acid) colorimetric

Vitamin C (ascorbic acid), being a part of the antioxidative defense system, is found in
both the cytosol and extracellular spaces. Depending on the concentration and the
availability of transitional metals, it has antioxidative as well as prooxidative features.
The antioxidative effect dominates, especially in extracellular space. Since it acts
through formation of semi-dehydro-ascorbate and dehydro-ascorbate respectively,
as an electron donor transferring hydrogen to acceptor substances by reversibility,
ascorbic acid has strong reducing effects.
Vitamin C contributes to the antioxidative defense system in two different ways: it
reacts with reactive oxygen species, especially peroxide radicals, and regenerates atocopherol
(vitamin E). Vitamin C also has a pro-oxidative effect in combination with
transition metals. It catalyses the reduction of Fe3+ to Fe2+. The created bivalent iron
ions react faster with H2O2. Therefore, the formation of OH• radicals is supported
through the Haber-Weiss-Reaction.
Due to the very small concentration of free transition metals in biological tissues, the
antioxidative features are predominant. As a result of increased oxidative stress, the
level of vitamin C is reduced in various syndromes, e.g. the level of vitamin C in blood
from HIV positive patients is significantly lower. The content in blood plasma falls
from 75.7µmol/l to 40.7µmol/l. Smoking causes a high consumption of vitamin C in
the blood plasma. Protein thiols are oxidised and after the Vitamin C pool has been
depleted, lipid peroxidation begins.