III Pharm.D -Medicinal chemistry/As per RGUHS syllabus-Preservatives

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PRESERVATIVES
BY
KENCHA SWATHI
ASSISTANT PROFESSOR
BANGALORE

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PRESERVATIVES
 Chemical agents that are added to various dosage
forms and cosmetics to prevent microbial contamination
are called preservatives.
 In parentral and ophthalmic preparations they are used
to maintain sterility in the event of accidental
contamination during the use.

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IDEAL PROPERTIES OF A PRESERVATIVE
 They should prevent microbial contamination
 should be non-toxic
 They should be stable
 Should be effective at low concentration against all possible
microorganisms.
 Compatible with other constituents used in the preparation
 A ideal preservative should be stable for the shelf life of the
preparation.

4. z CHEMICAL CLASSIFICATION
 Preservatives are chemically classified as 2 types:
1.Parahydroxy benzoicacid derivatives
2.Other preservatives

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PARAHYDROXY BENZOIC ACID DERIVATIVES
 This class of preservatives are ester derivatives(-COOR).
 They have antifungal properties.
 Their toxicity is generally low due to rapid hydrolysis of the esters and
they are rapidly conjugated and excreted.
 The activity increases by increase in molecular weight .
 But Methyl ester is effective against moulds whereas propyl ester is
more effective against yeast.
Eg: Methyl paraben,Ethyl paraben,Propyl paraben

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Methyl paraben Ethyl paraben
Propyl paraben

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OTHER PRESERVATIVES
Chlorobutanol Benzyl alcohol
2-Phenyl ethyl alcohol

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Phenyl mercuric nitrate Phenyl mercuric acetate
Sodium benzoate
Sodium propionate

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