Preservativeis a substance or chemical that is added to cosmetic product to prevent decomposition by microbial growth or by undesirable chemical changes.

1. ANTIMICROBIALS USED AS PRESERVATIVES,THEIR
MERITS AND DEMERITS,FACTORS AFFECTING
MICROBIAL PRESERVATIVE EFFICACY
UNDER THE GUIDANCE OF
Dr. G.V. RADHA
PRESENTED BY
DIVYA PUSHP [VP21PHAR0100004]
M.PHARM [PHARMACEUTICS]

2. INTRODUCTION
PRESERVATIVE
It is a substance or chemical that is added to cosmetic
product to prevent decomposition by microbial growth or by
undesirable chemical changes.
NEED OF PRESERVATIVES
 To prevent spoilage of cosmetic products.
 To stabilize the product.
 To increase the shelf life of the product.

3. Preservatives are used to prevent spoilage of cosmetic products.
• Main reasons for spoilage are:
 Oxidation of oils and fats
 Microbial growth
• All cosmetic preparations containing water as one of the ingredients
are susceptible to microbial growth.
• Microbes can attack even most anhydrous preparations like lipsticks.
• Cosmetic preparations containing oils and fats are also susceptible to
oxidative reactions.
• In view of this, cosmetic preparations containing oils and fats must be
preserved with antimicrobial agents and antioxidants.

4. IDEAL PRESERVATIVES SHOULD POSSESS THE FOLLOWING
ATTRIBUTES
 It should be compatible with the formulation.
 It should be colourless, and odourless or nearly so.
 It should be non-toxic, non-irritant or non-allergic in
concentrations used.
 It should remain stable to provide sustained anti-microbial
effect.
 It should be soluble to such an extent that effective
concentration is achieved.

5. ANTI-MICROBIAL AGENTS
• Microbes[bacteria, fungi, yeasts] are widely distributed in the nature.
• Sources of microbial contamination-
 Raw materials
 Environment
 Equipment
 Packaging materials
 Personnel
• Multiplication of microbes-
 Utilization of materials in their immediate surroundings
 During multiplication of microbes, complex chemical reactions occur
and a variety of metabolites are formed.

6. INDICATION OF DEGRADATION [IF PRESERVATION IS
NOT DONE PROPERLY]
• Moulds and fungi can be seen on the surface of the
product as they grow macroscopically.
• Bacteria in liquid preparations may be visible and may be
seen as turbidity and sedimentation.
• Colour changes may occur due to change in pH.
• Colour change may occur due to pigments produced by
bacteria.
• Some bacteria cause formation of gas which may be seen
as bubbles or froth in liquid preparations.

7. • Surveys were carried out and it revealed presence of a variety of microorganisms in
used and unused cosmetics.
• Used cosmetics were found to be contaminated with staphylococci, diphtheroids,
fungi and yeast.
• In unused cosmetics, pseudomonas were most frequently present.
• A list of salient compounds that can be used in cosmetics and pharmaceutical
preparations, is listed in table 1.
• But the number of compounds that can be used in cosmetics as preservatives is
quite limited.
• Reasons for this limitation are:
 They may impart an undesirable color.
 They may impart an undesirable odour.
 They may be toxic.
 They may be irritant
 They may be allergenic.
 They may be active only in a narrow Ph range

8. TABLE 1 PRESERVATIVES WHICH ARE USED IN COSMETICS AND
PHARMACEUTICAL PREPARATIONS

10. COMMONLY USED PRESERVATIVES ARE-
 Parabens
 Formaldehyde releasers
 Isothiazolinones
 Phenoxyethanol
 Organic acids
PARABENS
• Widely and economically used.
• Effective for fungal protection and some gram positive
bacteria.
• For protection from gram negative bacteria,it should be
combined with other preservatives
• Effective combination-Propyl: methyl paraben[1:2]

11. MERITS OF PRESERVATIVE
• Prevents the bacterial growth, spoilage.
• Keeps the product fresh for longer time.
• Improves the appearance of cosmetic product.
• Combination of esters exhibit increased activity.
DEMERITS OF PRESERVATIVE
• Can be toxic in larger concentration.
• Sometimes interact with the formulation.
• Incompatible with some proteins.
• Some non-ionic emulsifiers reduce the activity.

12. FACTORS AFFECTING MICROBIAL
PRESERVATIVE EFFICACY
1.Dissociation and pH
2. Concentration
3. Susceptibility of organisms
4. Interference by ingredients of cosmetics
5. Influence of solid particles

13. DISSOCIATION AND pH
• An ideal preservative should be effective in wide range of pH. However, in
practice, majority of preservatives are active in acidic range than in alkaline
range.
• Preservatives which are active in both acidic and alkaline pH ranges have
the disadvantage of being highly reactive in nature. For example,
formaldehyde and formaldehyde releasing compounds. These compounds
can react with other ingredients of formulation.
• There are many preservatives which are greatly influenced by pH. For
example, weak acids.
• Activity of weak acids depend on their undissociated amount of acid which
in turn depends on the dissociation constant and pH of the system.
• Simon has demonstrated that effectiveness of weak acids is influenced in a
regular manner by changes in pH.
• On the other hand, there are preservatives which are active only in
dissociated from. For example, cationics.
• Quaternary ammonium compounds are effective in higher pH (alkaline) but
these become ineffective in lower pH (acidic).
• Some preservatives may be pH dependent because of the stability problem.
For example, 2-nitro-2-bromo-propanediol(Bronopol) start deteriorating at
pH higher than 7.

14. CONCENTRATION
• Some materials used in cosmetic formulations have antimicrobial
action and, therefore, concentration of preservatives required may
be very less.
• There may be ingredients in cosmetics which promote growth of
micro-organisms, for example, mucilages of natural gums.
Concentration of preservatives, obviously will be more in such
products.
• Recommended effective concentration range from as little as 0.001%
(organic mercury compounds) to 0.5-1.0% (weak acids).
• Availability of preservatives to micro-organisms is more important
than overall concentration of preservatives which may depend upon
permeability across cell wall, diffusion rate, and degree of absorption
and partition coefficient of the preservative depending on the
mechanism of action.
• Concentration of preservatives may be reduced if more than one
preservative is used in combination.
• Some commonly used preservatives and their recommended
concentrations are given in table 2.

16. SUSCEPTIBILITY OF ORGANISMS
• Hydroxy benzoates are active against moulds, fungi and
yeasts but less active against bacteria.
• Chlorobutanol has antibacterial and anti-fungal activities.
• Phenyl mercuric nitrate is active against bacteria, fungi,
moulds and yeasts.

17. INTERFERENCE BY INGREDIENTS OF COSMETICS
• Several non-ionic surfactants such as Tween 80,Polyethylene glycol
1000 monocetyl ether, Polyethylene glycol400 laurate interfere with
activity of preservatives by exerting protective effect on micro-
organisms.
• Soaps and anionic surfactants in lower concentrations promote
growth of Gram-negative bacteria.
• Hydrophilic polymers like polyethylene glycols, gum tragacanth,
methyl cellulose, carboxy-methyl cellulose and polyvinyl-pyrolidone
have only marginal effect in reducing efficiency of majority of anti-
microbials.
• Addition of certain materials to the aqueous phase of emulsions help
in minimizing adverse effect of non-ionic surfactants on
preservatives.
• Materials like propylene glycol, glycerin and hexylene glycol have
been found useful in this respect.

18. INFLUENCE OF SOLID PARTICLES
• Some of the insoluble solid particles are kaolin, chalk, zinc
oxide, talc and pigments.
• Preservatives can be adsorbed on the surface of solid
particles.
• The extent of adsorption will depend on nature of solid
particles and pH of the preparation.
• Preservatives can also interact with plastics.
• Phenolic and quaternary ammonium compounds have
been reported to react with polyurethane.

19. GUIDELINES FOR SELECTING PRESERVATIVES
The following steps will help in selecting preservative(s) for developing a
cosmetic formulation. All the ingredients of a formulation should be checked
for their likelihood of contamination.
 Identify the materials which could promote the microbial growth, e.g.
• glycerin, sorbitol etc. (in concentration less than 5%);
• soaps and anionic surfactants below 15%;
• proteins;
• carbohydrates;
• cellulose derivatives;
• Gums.
 pH of aqueous phase should be found out as some preservatives are active
in acidic pH and others are active in alkaline pH.
 It should be estimated whether preservative will be partitioned between
two phases depending on formula of the preparation. If the preservative is
likely to leave aqueous phase leaving insufficient quantity to be effective,
see whether there is any material which is will reduce the partition
coefficient (e.g., propylene glycol, hexylene glycol).
 The ratio of total to free preservative should be estimated in presence of
macromolecules present in the formulation.
 The least toxic of the possible preservatives should be selected.

20. • The Indian Standard IS 4707 (part 2): 2001, Annex C has two parts.
Part 1 has list of preservatives allowed. Part 2 has list of preservatives
provisionally allowed. However, at present, no substance has been
listed in Part 2.
EVALUATION OF PRESERVATIVES
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

21. • 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.
It is recommended to carry out following parameter:
• Validation of preservation efficacy when freshly prepared in
laboratorial condition.
• Validation of preservation efficacy after end of storage in container to
show possible interference with the packaging material.
• Validation of preservation efficacy in first production batch ,just prior
to packaging.

22. 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)
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 the cultivation and
conservation of pathogenic and non-pathogenic fungi.
• Pharmacopoeia use saline solution to wash test strains before
inoculation instead of nutrient broth. The latter decreases inactivation
rate of the test organism comparatively with the saline solution
prepared for the strains grown on the agar.

23. d) Inoculation of samples : -
The inoculated test samples are incubated during 28 days, 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.
Other methods:-
a) D-value method- It is a 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.

24. REFERENCES
1. P.P. SHARMA. Cosmetics- formulation, manufacturing and
quality control, Vandana Publications Pvt. Ltd., 4th Edition
2. https://www.slideshare.net/pravinkshatriya/antimicrobial
-used-as-preservatives-230332763
3. https://www.slideshare.net/MahendraKumarPrajapa/anti
micribial-used-as-preservatives-their-merits-and-demerits

25. THANK YOU