This document discusses antimicrobial preservatives used in cosmetic products. It begins with an introduction to preservatives and their role in preventing microbial growth and decomposition. Commonly used preservatives like parabens, formaldehyde releasers, and isothiazolinones are listed. The need for preservatives to prevent spoilage and increase shelf life is explained. Ideal characteristics, classification, mechanisms of action, and factors affecting preservative effectiveness are overviewed. Methods for evaluating preservatives like challenge tests, test organisms, and inoculation of samples are described. The document concludes with references.

1. Antimicrobial used as
preservative
Under the guidence of ,
Mrs. S.S.MUTHA
M.PHARMACY
Presented by,
Mr. Pravin J. Kshatriya
M.Pharm 1st year
Department of pharmaceutics.
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2. Contents:
 Introduction
 Commonly used preservatives
 Need of preservatives
 Ideal characteristics
 Merits and Demerits of preservative
 Classification
 Mechanism of action
 Factors affecting effectiveness
 Evaluation of preservatives
 References.
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3. Introduction:
• Preservative is a substance or chemical that is
added to cosmetic product to prevent
decomposition by microbial growth or by
undesirable chemical changes.
• This are antimicrobial agents which maintains
the microbiological safety of cosmetic
products by inhibiting growth of microbes.
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4. • Commonly used preservatives:-
1) Parabens.
2) Formaldehyde releasers.
3) Isothiazolinones.
4) Phenoxyethanol.
5) Organic Acids.
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5. Need of Preservatives:
• To prevent spoilage of cosmetic products.
• There are two main reasons for spoilage of
cosmetics : 1) Oxidation of oils and fats.
2) Microbial growth.
• To stabilize the product.
• To increase the shelf life of product.
• Water promotes growth of micro-organisms so
there is need of preservative in anhydrous
cosmetic preparation.
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6. Ideal Characteristics:
Compatible
with drug
components
Odorless
Tasteless
Effective
Cost
effective
Non-toxic
and non
reactive
Stable
Highly
soluble
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7. • Merits
It should prevent the bacterial growth
,spoilage.
Keep the product fresh for longer time.
Something that improves appearance of
cosmetic product.
Combination of esters exhibit increased
activity.
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8. • Demerits
Can be toxic in larger concentration.
Sometime interaction with formulation.
Incompatible with some proteins.
Some non-ionic emulsifiers reduce the
activity.
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9. Classification:
1) Based on mechanism of action :
a) Antioxidants – Vitamin E, Vit. C
b) Antimicrobial agent – Benzoate, Na benzoate.
c) Chelating agents – Citric acid, polyphosphates.
2) Based on source :
a) Natural – Lemon, honey.
b) Artificial – Propionates, nitrites.
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10. Mechanism of action:-
• Most preservatives when come in contact
with the cell membrane and cell wall fractions.
• They react with proteins, disrupts microbial
cell protection structure or interfere with cell
and affect the normal cell growth.
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11. Parabens:-
• Widely and economically used.
• Effective for fungal protection and some Gram
positive bacteria.
• For protection from Gram negative bacteria ,
should be combined with other preservatives.
• Allowed for rinse-off and leave-on products.
• Effective combination - Propyl : methyl
paraben (1:2)
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12. Factors affecting effectiveness:-
• Dissociation and pH
• Concentration
• Susceptibility of organisms
• Interference by ingredients of cosmetics
• Influence of solid particles
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13. Dissociation and pH:-
• Different cosmetics have different pH and
different microbes grow at different pH.
• Majority of preservatives are active in acidic
range than in alkaline pH.
• pH influences preservative efficacy.
• Weak acid’s activity depend on undissociated
amount and undissociation depends on
dissociation constant and pH.
Example – Methyl parabenzoic acid is approx. 50%
dissociated at pH 8.5, so effiacacy is reduced by
almost 50% at pH 8.5.
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14. Concentration:-
• Some materials used in cosmetic have
antimicrobial action, so concentration required
is less.
• Some ingredients promotes growth of microbes,
so concentration required is more.
• Effective concentration range is from 0.001%
(organic mercury comp.) to 0.5-1% (weak acids).
• If combination of preservative used,
concentration required is less
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15. Susceptibility of organisms:-
• Different antimicrobials have different activity
against microbes.
Examples:
• Hydroxy benzoates active against moulds,
fungi, yeast and less active against bacteria.
• Chlorbutanol has antibacterial and anti-fungal
activity.
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16. Interference by ingredients:-
• Non-ionic surfactant like Tween 80 , PEG 1000,
PEG 400 interfere with activity of preservative by
exerting protective effect on micro-organism .
• Soaps and anionic surfactants in lower
concentrations promote growth of gram negative
bacteria .
• Hydrophilic polymer like PEG ,gum tragacanth,
carboxy-methyl-cellulose and methyl cellulose
have reducing efficiency of anti-microbial.
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17. Influence of solid particles:-
• Some cosmetics containing insoluble solid like
kaolin , chalk, zinc oxide, talc.
• Preservative can be absorbed on the surface
of the solid particles.
• Adsorption depend on nature of solid
particles.
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18. Evaluation of preservative :-
The evaluation of preservative has traditionally
involved the following tests :
Preservative efficacy tests (PET).
a) Challenge test
b) Test organisms
c) inoculum
d) Inoculation of sample
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19. • Preservative efficacy test used to assess
efficacy of preservative in final product .
• Several tests recommended by different
laboratories but challenge test is method
adopted by international regulation.
a)Challenge test:-
Challenge test assessment related to stability
of formulation during manufacturing ,storage
and its use by consumer.
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20. 20
• It is recommended to carry out following
parameter:
i. Validation of preservation efficacy when
freshly prepared in laboratorial condition .
ii. Validation of preservation efficacy after end
of storage in container to show possible
interference with the packaging material .
iii. Validation of preservation efficacy in first
production batch ,just prior to packaging .

21. b) Test organism :-
• The specific strains used in these tests can be
obtained from official cell culture collections,
such as American Type Culture Collection
(ATCC). The most common test strains are
Gram positive bacteria ( staphyloccus aureus)
Gram negative bacteria (e.coli)
Molds ( aspergillus niger)
Yeast (candida albicans )
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22. c) Inoculum :-
• A medium such as a tryptic soy agar ( soybean
–casein digest agar) support vigorous growth
and is recommended for the initial culture of
bacteria .
• Dextrose agar is a non-selective medium is
used for a the cultivation and conservation of
pathogenic and non- pathogenic fungi.
• Pharmacopoeia use saline solution to wash
test strains before inoculation instead of
nutrient broth.
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23. • The later decreases inactivation rate of the
test organism comparatively with the saline
solution prepared for the strains grown on the
agar .
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24. d) Inoculation of samples :-
• The inoculated test samples are incubated
during 28days ,varying the condition between
room and high temperature, temperature
between 20-25 C . Support the growth of
micro-organism and their possible reaction
with preservative active ingredients.
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25. Other methods:-
• a) D-value method-
• It’s quick method to estimate the effectiveness of
preservatives .this method can be used to
determine the shelf life of cosmetic products
within 48 h for bacteria and yeasts , and seven
days for mold .
• b) Capacity test –
• The capacity test evaluates the effectiveness of
the preservative concentration, and antimicrobial
activity of the creams, suspension, and solutions.
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26. References:-
 P. P. Sharma. Cosmetics - formulation,
manufacturing and quality control, Vandana
Publications Pvt. Ltd.,4th edition 2008, pg.no: 79-
83, 182-183.
 M .S. Balsam, E. Sagarin. Cosmetics–Science and
technology . Krieger Publishing Company, Second
edition, Volume 1st , pg.no:- 206-208.
 M.S .Balsam , E.Sagarin . Cosmetics- science and
technology . Krieger Publishing Company, second
edition, volume 3rd , pg .no : 391-470.
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27. •Thank you
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