Antioxidant

Antioxidant

Ø  ANTIOXIDANT :

Antioxidant are the agent which inhibit in oxidation and commonly used to prevent rancidity of oil and fats.

Ø  Mechanism of action :

1.                  The mechanism of action of inorganic antioxidant is same as like Redox reaction

2.                  In redox reaction, there is transfer of electron from one compound to another

3.                  Oxidation is loss of electron and reduction is gain of electron

·        Oxidation + e-àReduction

4.                  When a substance act as antioxidant it get oxidiseditself and prevent the oxidation of active pharmaceutical species

Ø  TYPE OF ANTIOXIDANT

1.                  Inorganic

2.                  Oxidation

1.                  Inorganic antioxidant :

e.gHypophosphorousacid , sodium metasulphite, sulphur dioxide, sodium nitrate, etc.

2. Organic antioxidant :

a. Quinol group: Trocopherol, Hydrochromanas,hydroxylcoumarans.

b. Pyrogallolgroup : Amyl gallate,  n- propyl gallate .

c. Amines: cephalins, lecithin .

d. Benzoic acid: Methyl propyl parabens.

Ø  SELECTION OF INORGANIC ANTIOXIDANT

1.      They should be non toxic .

2.      They should be chemically and physiologically compatible .

3.      They should be chemically inert .

4.      They should not create any solubility problem in  either its reduced or oxidisedfrom

Ø  EXAMPLE :

1.                  Hypophosphorous acid  (H₃PO₂):

·         Preparation:

It is obtained by decomposing a boiling aqueous solution of a calcium hypophosphite with oxalic acid.

The insoluble precipitated of calcium oxalate is filtered and filterate is concentrate by evaporation.

·        Ca(HPH₂O₂)₂+ H₂C₂O₄.2H₂O  --àCaC₂O₂. H₂O + 2HPH₂O₂+ H₂O

·        Properties:

1.      It is colourless,slightly yellowish liquid.

2.      It is odourless.

3.      It is syrupy in nature but from crystalline solid at 17.4°c.

4.      It acts as a powerful reducing agent.

·        Uses

1.      It is mainly used as antioxidant.

2.      It is also used in syrup as a reducing agent.

·        Incompatibility

It is incompatible with mercury , silver, lead, etc.

·        Storage

It is stored in tightly closed , light resident.

2.                  Sulphur dioxide (SO₂):

·        Preparation:

 It is prepared by by large or small scale.

On the laboratory scale , it can be prepared by burningsulphur in presence of air or oxygen.

2S₂ + 2O₂ à 2SO₂

On industrial scale ,it is prepared by roasting metallic sulphide

Cu₂S+2O₂à 2CuO + SO₂

                            2ZnS + 3O₂ à 2ZnO + 2SO₂

·        Properties

1.    It is. Colorless ,not inflammable gas  with pungent odour

2.    The gas is soluble in water and alcohol.

3.    Aqueous solution of gas is acidic   in nature and acidic to litmus

·        Uses

1.      It  is also used as antioxidant

2.      it is used as antibacterial & antifungal.

3.      It is also used as preservative for food, dry fruits and fruit juices.

4.      it is used in industry to bleach and refine the syrup

5.      it is used in sugar factory.

·        Incompatibility

It is incompatible with oxidizing agent and thiamin

3.sodiummetabisulphite ( Na2S2O5)

It is also called as sodium Pyrosulphite anddisodiuespyrosulphite

·        Preparation

1.Itis obtained by passing sulphur dioxide  gas  through a hot solution of NaOH.

2. In this process , a sodium bisulphite is formed which decomposes to gives sodium metasulphite.

NaOH + SO₂                   NaHSO₃      

2NaHSO₃Na₂S₂O₅ + H₂O

·        Properties

1.It occurs as whitish yellow powder having anodourof  ( sodium dioxide).

2. It is soluble in water and forms sodium bisulphite.

3. It is a strong reducing agent .

·         Uses

1.It is used as an antioxidant

2. It is used as a preservative in many suspension ascorbic  injection .

3. It is useful as stabilizer.

4. It is used as preservative in syrup.

4. Sodium bisulphite( NaHSO3)

 It is also called as sodium hydrogen sulphite or sodium acid sulphite.

·         Preparation

1.It is obtained by passing sodium hydroxide through a hot solution of NaOH.

2. In this process sodium bisulphite is formed.

NaOH + SO2 à  NaHSO3

3.It is also obtained by dissolving sodium metabisulphite in a water it get converted to sodium bisulphate.

        Na2S2O5 + H2O --à NaHSO3

·         Properties

1.It occurs as whitish yellow powder having aodour of  sodium dioxide.

2. It is soluble in water.

·        Uses

1.It is used as an antioxidant.

2. It is used as preservative.

3. It is used as stabilizer.

4. It is used as preservative in syrup.

·        Incomparibility

It is  in compatible with thyamine.

5.soudium nitrite( NaNO2)

·        Preparation

1.Itis prepared by obsorbing nitrogen oxide and oxygen into a solution  carbonate the solution concentrated to crystallized out the product.

2 Na2CO3 + 4NO + O2 -à 4 NaNO2 + 2C2

·         Properties

1.It is occurs in the form of white granular powder or white crystal with saline test salty.

2. It is soluble in water and sparingly soluble in alcohol.

3. When it is exposed to atmosphere it get oxidize to sodium nitrate .

·        Uses

1.pharmacologically , it act on relaxation of  smooth muscles and share vasodition action on blood vessel

2. It is also used in anginapectoris.

3. It is used as antioxidant.

4. It is also used as antidote in cyanide poisoning.

5. It is also used as preservative for food.

·         Storage

It is stored in the air tight container.

6.      Sodium Thiosulphide( Na2 S2O3)

·        Preparation

1.It is prepared from Na2CO3 ( soda ash) SO2 and sulphure.

2. Soda ash is dissolved in water into which SO2 is passed , the resulting solution is treated with the remaining quantity of soda ash , which is then heated with sulphur.

3. The solution is allowed to settle and then crystallized.

Na₂CO₃ + H₂O + 2SO₂               2NaHSO₃ + CO₂

2NaHSO₃ + Na₂CO₃                                             2Na₂ SO₃ +H₂O + CO₂

Na₂SO₃ + S                                                         Na₂ S₂O₃

·         Properties

1.It occurs as transparent, colorless, prism of crystalline powder.

2. It has cooling , bitter in taste .

3. It is soluble in water , but in soluble in alcohol.

·        Uses

1.It is useful in skin diseases and ring worm infection.

2. It is effective in cyanide poisoning as an antidote.

3. It is also used in photographic industries.

·        Incomparibility

It is incompatible with oxidizing agent heavy metal and acids.