Download Ascorbate

In the Name of The Most High
Vitamin C
&
its Antioxidant Chemistry
OH
O
HO
HO
O
OH
Ascorbic Acid
Physical data
Appearance: white to light yellow crystals or powder
Melting point: ca. 193 C (decomposes)
Specific gravity: 1.65
Water solubility: high
Stability
Stable. May be weakly light or air sensitive. Incompatible
with oxidizing agents, alkalies, iron, copper.
Toxicology
May be harmful if ingested in large quantity.
May act as an irritant.
Orl-Rat LD50 11900 mg/kg
Sucrose
Orl-Rat LD50 29700 mg/kg
Sodium Chloride
Orl-Rat LD50 3000 mg/kg
Ascorbic Acid is a Di-acid
OH
O
HO
OH
O pK = 4.1
1
OH
HO
AscH2
O
HO
O
OH
O
O
pK2 = 11.8 HO
OH
O
AscH
O
2-
Asc
Ascorbates
At
pH 7.4
99.95% of vitamin C will be present as AscH, 0.05% as AscH2 and 0.004% as Asc2-.
The antioxidant chemistry of vitamin C is the chemistry of AscH- .
O
-
AscH
a Donor Antioxidant
OH
O
HO
OH
+
OH
O
AscH
O
HO
O
O
R
+ RH
O
O
Asc
AscH- donates a hydrogen atom (H· or H+ + e-) to an
oxidizing radical to produce the resonance-stabilized
tricarbonyl ascorbate free radical.
AscH· has a pKa of -0.86; thus, it is not protonated in vivo
and will be present as Asc·-.
Ascorbate
a versatile, water soluble, donor antioxidant.
OH
O
HO
OH
+
OH
O
AscH
O
HO
O
O
R
+ RH
O
O
Asc
A weakly oxidizing
and
weakly reducing radical
Reactive Oxygen and Nitrogen Radicals
(both inorganic and organic)
Reactive oxygen Radicals
Superoxide, O2•
Hydroxyl, OH•
Peroxyl, RO2•
Alkoxyl, RO•
Hydroperoxyl, HO2•
Reactive nitrogen Radicals
Nitrogen oxide, NO•
Nitrogen dioxide, NO2•
Peroxynitrite, ONOO •
There are four types of ROR/RNR damages
Damage to fat compounds
Attack the fatty membranes surrounding the cells
loose its ability to transport oxygen, nutrients or water to the cells.
Damage to protein molecules
Attack the nucleic acid
The nucleic acids function is to regulate the normal
cell function, growth and also to repair the damaged tissues.
Cell damage
Damages done to the chromosomes and nucleic acids
The first step in cancer development
Lysosomes damages
The enzymes leak out when the membrane cell breaks and they start
digesting the cell itself
Lower the immune system resistance
ROR/RNR redox signaling
Stimulating cell growth
Programmed cell death
Induction of mobilisation of ion transport systems
Diseases
Inflammation
Cardiovascular disease
Ageing
Neurodegenerative diseases
such as Parkinson's disease Alzheimer's disease
Cancer
Obesity
The free radical theory of aging
Cells continuously produce free radicals
Constant radical damage eventually kills the cell
When radicals kill or damage enough cells in an organism,
the organism ages.
The production of radical oxygen,
the most common radical in biological systems,
occurs mostly within the mitochondria of a cell.
The primary site of radical oxygen damage
is mitochondrial DNA (mtDNA).
mtDNA cannot be readily fixed.
Extensive mtDNA damage accumulates over time
and
shuts down mitochondria,
causing cells to die and the organism to age.
Some cellular antioxidants
enzymes such as
Superoxide dismutase,
Catalase
Glutathione Peroxidase
Peroxiredoxins
and
Sulfiredoxin
Small molecule antioxidants such as
Ascorbic acid
(vitamin-C)
play important roles as cellular antioxidant.
Thank You