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Chapter-1(A). Preservatives – Associated Problems and Alternative Solutions

Development and evaluation of novel preservatives from simple organic acids

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1. Preservatives- associated problems and alternative solutions

1.1 Introduction

Non-sterile products such as pharmaceuticals, cosmetics, food items etc. with a high

degree of water availability may be contaminated with microorganisms. The

microorganisms may cause spoilage of the product with loss of therapeutic properties

and, if they are pathogenic, serious infections can arise (Zani et al., 1997). There are

many factors (Table 1) which potentially contribute to the microbial load carried by a

pharmaceutical preparation at every stage of manufacture, from assembling the raw

materials to packaging the final product (Aulton et al., 2002).

Table 1. Sources of microbial contamination

S.No. Source Contaminant

1 Water Low demand Gram negative groups:

Pseudomonas, Xanthomonas,

Flavobacterium, Achromobacter

2 Air Mould spores: Pencillium, Mucor,

Aspergillus

Bacterial spores: Bacillus spp.

Yeasts : Micrococci

3. Raw material

Earths

Pigments

Starches

Gums

Anaerobic spore formers Clostridium spp.

Salmonella

Coliforms

Achnomyces

4 Personnel Coliforms, Staphylococci, Cornye bacteria

1.2 Preservatives

To inhibit the growth of contaminating microorganism, antimicrobial preservative

systems have been developed and introduced into the pharmaceutical, cosmetic or

food products during manufacturing process and/or throughout its use by consumers

(Denyer et al., 1988). A preservative may be synthetically produced or a naturally

occurring substance that is added to products such as foods, cosmetics, paints,

pharmaceuticals, wood, etc. to prevent decomposition by microorganisms or

undesirable chemical changes.

1.3 Classification of preservatives:

Preservatives may be categorized as per their area of application such as

pharmaceutical , cosmetic , wood and food preservatives etc. Preservatives are

basically of two types: naturally occurring and chemically derived, so the



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classification as per their source either natural or chemical is illustrated in Table 2 and

Table 3 and the structures of various chemical preservatives are shown in Fig. 1.

Table 2: Natural preservatives and preservation techniques.

(www.naturalingredient.org/Preservatives original.pdf)

(http://en.wikipedia.org/wiki/Food_preservation)

Preservative agent/process Preservative application

Salt Meat curing by inhibition of Clostridium botulinum

Rosemary extract Lotions and creams in cosmetics

Sugar Fruits as apples, pears, peaches, apricots, plums

Vinegar Chips, crisps, beetroots

Alcohol Pharmaceutical preparations- medicated and non-

medicated syrups

Diatomaceous earth Food preservation

Freezing Meat , fruits, jams, jellies, cosmetics

Pickling Fruits, vegetables

Smoking Food preservation

Drying Food preservation

Vacuum Packing Pharmaceuticals, cosmetics and food

Jellying Fruits preservation

Potting Meat as in chicken liver preservation

Jugging Meat pieces sealed with gravy

Citric acid Fruits preservation

Ascorbic acid Fruit preservation

Irradiation Food , surgical dressings

Sugar Vinegar Potting

Freezing Pickling Salting



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Table 3: Classification of chemical preservatives (Denyer et al., 2004).

Chemical Class Name of preservatives

Hypochlorites Sodium sulphite, sodium metabisulphite, sodium

bisulphite, potassium hydrogen sulphite

Aldehydes Glutaraldehyde, formaldehyde

Epoxides Ethylene oxide

Mercurials Phenyl mercuric nitrate, thiomerosal

Organic Acids Benzoic acid, sorbic acid, sodium sorbate, sodium

benzoate, salicylic acid, propionic acid

Furan derivatives Nitrofurazone, furazolidone, nitrofurantoin

8- hydroxy quinolones Chloroxime, 8- hydroxy quinoline

Alcohols Ethanol, isopropyl alcohol, benzyl ethyl alcohol,

benzyl alcohol, chlorbutanol

Phenols Phenol, m-cresol, 4-chloro-3-methyl phenol,

bronabol, chlorophene

Dyes

9-Aminoaciridine, methylene blue, gentian violet,

basic fuchsin

Parabens Methylparaben, ethylparaben, propylparaben,

butylparaben, isopropylparaben, isobutylparaben

Antioxidants Butylated hydroxyanisole(BHA), Butylated hydroxy

toluene (BHT), ter-butylhydroquinine(TBHQ)

Anilides Carbanilide

Chelating agents EDTA, Lecithin

Quaternary ammonium

compounds

Benzalkonium chloride (BAC), dimethyl dioctadecyl

ammonium bromide (DDAB), benzethonium

chloride

Biguanides Chlorhexidine

Miscellaneous

Bis-biguanides – Chlorhexidine.

Lactones - -propiolactone.

Sulfur – Sublimed sulfur, precipitated sulfur etc.

Amides – Tribromsalan, dibromsalan

Essential oils – Pine oil, -terpineol



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COOCH3OH

COOC2H5OH

COOC3H7OH

COOC4H9OH

COOH

COONa

CH3CH=CHCH=CHCOOH

CH3CH=CHCH=CHCOONa

Sorbic Acid

Sodium Sorbate

Methyl Paraben

Ethyl Paraben

Propyl Paraben

Butyl Paraben

Benzoic Acid

Sodium Benzoate

HgNO3

Phenyl Mercuric Nitrate

COONa

S

Hg CH3

Thiomerosal

CH2OH CH2CH2OH

Benzyl Alcohol Phenyl Ethyl Alcohol

Br NO2

OH OH

OH CCl3

Bronabol Chlorbutanol

OH

OH

CH3

OH

CH3

Cl

4-Chloro-3-methylphenol

Phenol

m-cresol

N+ Cl -

Benzalkonium Chloride

(CH2)11

MeMe

Me

+

Br -

Cetrimide

N+

(CH2)14

CH3

Cl-

Cetylpyridinium Chloride

N+

OO Cl-

Benzethonium Chloride

Chlorhexidine

Cl

HN

HNNH

HNNH NH

NH

NHNH

NH

Cl

Fig.1: Structures of chemical preservatives commonly used in food and

pharmaceuticals



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1.4 Different methods of preservation:

Preservation of food and pharmaceuticals is a continuous fight against

microorganisms that are spoiling or making them unusable. The preservation can be

achieved by any one of the methods as shown in Fig.2 (Devilieghere et al., 2004).

Fig. 2: Various methods of preservation of food and pharmaceuticals.

1.4.1 Traditional food preservation methods:

a) Chemical preservative agents:

Chelators: Chelators that can be used as food additives includes the

naturally occurring citric acid and EDTA as its disodium and calcium salt s.

EDTA potentiates the effect of weak acid preservatives against Gram

negative bacteria, and citric acid inhibits the growth of proteolytic

Clostridium botulinum due to its calcium (Ca2+

) chelating activity (Graham

et al., 1986).

Hydrogen peroxide: Hydrogen peroxide liberates a short-lived singlet

oxygen species, that is highly biocidal when used as preservative in food

items. Production of super oxide radical from hydrogen peroxide may

combine with hydrogen peroxide in presence of Fe2+

to form the extremely

biocidal hydroxyl radical. Hydrogen peroxide itself is an effective

sporicidal agent at elevated temperatures (Luo et al., 1994).

Organic acids: Preservative agents which are being used very commonly

belong to organic acids such as lactic, sorbic, benzoic acids etc. Growth

inhibition of microbes by acid preservatives may likely be due to inhibition

of essential metabolic reactions, membrane disruption, stress on

intracellular homeostasis or accumulation of toxic anions in microbes

(Stratford et al., 1998).



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b) Naturally occurring preservatives:

Small organic biomolecules:

Antibacterial activity of carvacrol, (+)-carvone, thymol and trans-

cinnamaldehyde against E. coli and S. typhimurium has been reported

(Helander et al., 1998).

The small organic molecule like eugenol (clove), essential oils from

plants such as caraway, coriander etc. have inhibitory effects on

organisms such as Aeromonas hydrophilia, Pseudomonas fluorescence

and Staphylococcus aureus (Wan et al., 1998).

Isothiocyantes derived from garlic and onion, were reported to have

antimicrobial properties.

Membrane perturbing proteins and peptides:

The inhibitory effect of naturally occurring antimicrobial proteins and

peptides is normally due to disruption of membrane. Plants contain

defensins (membrane perturbing proteins), which protect them from

microbial infection (Anzlovar et al., 1998).

Nisin and pediocin are the only used protein based antimicrobials in

food industry (Hansen et al., 1994).

1.4.2 New preservation technologies

a) New packaging systems: New packaging systems have contributed significantly

in extending the shelf life of chilled minimally processed food products. The various

methods of new packaging systems may be as follows:

Packaging in CO2 atmosphere: Products susceptible to microbial spoilage due to

the development of yeasts and Gram-negative bacteria will be packed in CO2

atmosphere which retards their growth (Devilieghere et al., 1998).

Modified atmosphere packaging (MAP): This involves enclosure of food

products in gas barrier materials, wherein the gaseous environment has been

changed (Young et al., 1988).

Addition of antimicrobial agents in packaging materials: The incorporation of

antimicrobial substances (nisin, sorbic acid) in food packaging materials may be

done to control the growth of microorganisms on the surface of the food

(Vermeiren et al., 1999).



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b) Non-thermal inactivation technologies:

Pulsed electric fields (PEF):

The destruction of microorganism is caused by the application of

short high-voltage pulses between the set of electrodes causing

disruption of microbial cell membranes (Wuytack et al., 2001).

Inactivation of Bacillus subtilis and Bacillus cereus spores realized

by high voltage PEF in salt solution (Marquez et al., 1997).

High hydrostatic pressure (HHP):

HHP is the technology by which a product is treated at or above 100

Mpa e.g. this technique has been applied to improve the shelf life of

goat cheese as well as to reduce the ripening time of cheese to 3 days

at 250 Mpa pressure in dairy industry (Capellas et al., 1996).

1.4.3 Biopreservation:

In biopreservation, shelf life of food and pharmaceutical products can be

increased by addition of natural or controlled microflora, such as lactic acid

bacteria (LAB) and their antibacterial products such as lactic acid, bactericins

etc.

Bacteriocinogenic cultures: Bacteriocin such as nisin from

Lactobacillus lactis, pediocin from Pediococcus acidilactici and

sakacins from Lactobacillus sakei strains are comprised of a diverse

group of ribosomally synthesized extra cellular antimicrobial proteins or

peptides, which have a bactericidial or bacteriostatic effect on other

closely related bacteria. They acts generally on the cytoplasmic

membrane and dissipate the proton motive force through formation of

pores in the phospholipid bilayer (Ansari et al., 2005).

Nonbacteriocinogenic cultures: Nonbacteriocinogenic cultures such as

Lactobacillus alimentarius BJ-33, Lactobacillus sakei TH-1 and

Lactobacillus lactis strains shows significant preservative activity

(Bredholt et al., 2001). The antagonistic character of these cultures is

based on the production of lactic acid and acidification causing growth

inhibition of spoilage and pathogenic bacteria (Juven et al., 1998).



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1.5 Official status of pharmaceutical preservatives

Pharmacopoeias describe the status of various preservatives being used in the

pharmaceutical products and the preservatives which are official in pharmacopoeias

are presented in Table 4.

Table 4. Preservatives commonly used in pharmaceutical products. [I.P (1996) and

U.S.P.23 NF.18 (2004)]

S.No. Product

Type

Preservative Official

Status

Concn. (%W/V)

1 Parenteral

Benzyl alcohol USP 0.1-3.0

Methyl/propyl paraben USP 0.08-0.1 / 0.001-

0.023

Phenol USP 0.2-0.5

Methyl paraben USP 0.1

Chlorbutanol USP 0.25-0.5

Sodium metabisulphite IP 0.025-0.66

2 Ophthalmic Benzalkonium chloride IP 0.13-0.2

Thiomersol USP 0.0025-0.0133

Methyl/propyl paraben USP 0.001-0.5

Benzalkonium chloride +

EDTA

IP 0.05/0.01

3 Oral Sodium benzoate IP 0.01/0.1


4 Creams Benzyl alcohol IP 0.001-0.2


Methyl paraben USP 0.02-0.2 / 0.01-

0.04

Benzoic acid IP 0.1-0.3

Sorbic acid IP 0.2

Chlorcresol IP 0.1

1.6 Mechanism of antimicrobial action:

The antimicrobial agents that may be used as preservatives to make the

product stable may kill the microorganisms by entering into the cell wall

disrupting the various functional groups/sites or may change the structure of

DNA. So, the various mechanisms of antimicrobials of various categories are

enlisted in Table 5.



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Table 5: Mechanism of antimicrobial action of various classes of preservatives

(Hugo et al., 2004)

Chemical

Class

Targetting site

Hypochlorites -SH group of bacterial cell cytoplasm

Aldehydes -SH group of bacterial cell cytoplasm

-NH2 group of bacterial cell cytoplasm

Epoxides - SH group of bacterial cell cytoplasm

-NH2 group of bacterial cell cytoplasm

Mercurials Cytoplasmic coagulation

Organic Acids Acts on bacterial cell membrane ATPase and cause

inactivation

Alcohols Increases lipid solubility and cross bacterial lipid layer and

interrupts with cytoplasmic constituents

Chlorhexidine Membrane disruption

Parabens Acts on bacterial cell membrane ATPase and cause

inactivation

Acridines Induce alterations in ultrastructural changes in DNA

Cationic agents -COOH groups of bacterial cell cytoplasm

1.7 Characteristics of ideal preservative:

Preservatives which are being used in various food and pharmaceuticals may face

some disadvantages such as the microbial resistance, toxicity, incompatibility with

other ingredients, low solubility and lack of thermal stability. The characteristics of an

ideal preservative are summarized in Fig. 3.

1.8 Pathogenicity of microorganisms

Not all the microorganisms have an equal probability of causing infection and disease

but microbial pathogenicity has been defined as the biochemical mechanisms whereby

microorganisms cause disease. Probably any microorganism which has the capacity to

sustain itself in humans and cause disease in compromised individuals can act as an

opportunistic pathogen. Hence, infection and disease are inter-dependent on the host



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and the microorganism (Finley et al., 1989). The presence of pathogenic

microorganisms in food and pharmaceutical products can cause a lot many problems

for the consumers of these products. Some common pathogenic microorganisms are

enlisted in Fig.4.

Fig.3: Characteristics of an ideal preservative (Lundov et al., (2009)

Fig.4: Some common pathogenic microorganisms (Kaplan et al., 2005; Stins et al.,

2001 and Cheng et al., 2004)



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The pathogenicity of common microorganisms such as Staphyloccoccus aureus,

Bacillus subtilis, Escheirchia coli, Candida albicans and Aspergillus niger are

discussed over here.

1.8.1 Pathogenicity of Bacillus subtilis:

Contamination of food products with Bacillus subtilis may cause undesirable changes

in flavor, aroma or colour that may be due to the production of complex chemical

molecules 2,3,5-trimethylpyrazine and 2,3,5,6-tetramethylpyrazine. (Hauge et al.,

1955). Most isolates of Bacillus thuringiensis, Bacillus subtilis, Bacillus circulans,

Bacillus laterosporus, Bacillus icheniformis, Bacillus lentus and Bacillus mycoides

were positive with the cytotoxicity assay (Whitfield et al., 1998). Poisoning of food

with Bacillus species may cause vomiting and diarrhoea.

1.8.2 Pathogenicity of Staphylococcus aureus:

Due to high incidence, morbidity and antimicrobial resistance, Staphylococcus aureus

infections are growing concern for physicians. S. aureus is associated with various

skin and soft-tissue infections including impetigo, carbuncles, folliculitis, hidradenitis

and cellulitis. S. aureus is commonly isolated microorganism in osteomyelitis and

more than one third of these isolates are MRSA (Lobati et al., 2001). Post-influenza

pneumonias, necrotizing fasciitis, pyomyositis, and Waterhouse-Friderichsen

syndrome are caused by community acquired methicillin resistant S. aureus (MRSA).

S. aureus is a common pathogen in skin, pulmonary, soft-tissue, bone, joint and

central nervous system infections. S. aureus bacterias are particularly problematic

because of the high incidence of associated complicated infections, including

infective endocarditis (Bamberger et al., 2005). Staphylococcal food poisoning (SFP)

is a common cause of gastroenteritis worldwide and etiologic agents of SFP includes

mainly the S. aureus. Repeated ingestion of a contaminated milk produced symptoms

of vomiting and diarrhea, which may be the primary evidence that a soluble exotoxin

was responsible for SFP.

1.8.3 Pathogenicity of Aspergillus niger:

Aspergillus fumigatus is responsible for over 90% of cases of invasive aspergillosis.

Aspergillus spp. is progressively associated with a growing spectrum of infections in

immunocompromised hosts. Like Penicllium, Aspergillus species may produce toxins

that exhibit wide range of toxicities, with the most significant long term effects

(Araujo et al., 2004).



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1.8.4 Pathogenicity of Candida albicans:

Fungal infections caused by Candida species (candidemia) may be invasive and have

increased significantly and is associated with a mortality of about 30% to 40% and

also increases the cost for medical care. Candidemia patients usually face an acute

septic syndrome that is indistinguishable from bacteremia, and may also exhibit fever

of unknown origin. Candida albicans is an opportunistic human pathogen which

colonizes at several anatomical distinct sites oral, skin, vagina and gastro intestinal

tract (Yang et al., 2003). Recently, Candida species associated with candidemia have

shifted from Candida albicans to non-albicans Candida species (NAC) which is

approximately half of the total reported cases of Candida infections (Cheng et al.,

2004). Candida albicans, is a dimorphic commensal organism of the genital and

gastrointestinal tracts, is causative agent of VVC (vulvovaginal candidiasis) that is a

mucosal infection (Fleury et al., 1981).

1.8.5 Pathogenicity of Escherichia coli:

Escherichia coli is the most abundant facultative anaerobic gram-negative bacterium

of the intestinal microflora, naturally colonizing the mucous layer of the colon. EHEC

(Enterohemorrhagic E. coli) is responsible for outbreaks of hemolytic uremic

syndrome (HUS) and bloody diarrhea. Intervention and treatment strategies for EHEC

infections are quite controversial to that of conventional antibiotics which may be

harmful by increasing the probability of patients developing hemolytic uremic

syndrome (HUS) (Kaper et al., 2004). Further, recent studies have shown that

Escherichia coli is one of the important pathogens that may cause meningitis and may

cross blood brain barrier to the central nervous system (CNS) without altering its

integrity (Stins et al., 2001).

1.9 Problems Associated with the Existing Preservatives:

Apart from the increasing pathogenicity of microorganisms, the bacterial resistance to

preservatives fostered the researchers in search of new antimicrobial agents.

Examples of preservatives and biocides to which resistance has been reported

includes benzoic acid, benzalkonium chloride, chloramine, chlorhexidine,

cholorophenol, dibromodicyanobutane, dimethyl oxazolidine, dimethyl

dithiocarbamate, dimethoxy dimethyl hydantoin, formaldehyde, glutaraldehyde,

hydrogen peroxide, iodine, mercuric salts, methylene bischlorophenol,

methylparaben, propylparaben, phenylmercuric acetate, povidine-iodine, quaternary



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ammonium compounds and sorbic acid (Chapman et al., 1998). The preservatives

which are in very common use may also cause very serious side effects such as:

Cytotoxicity

Mutation

Decreased reproduction potential

Breast cancer

Contact eczema

Ocular disturbances

Asthama

Disruption of Vitamin B1

Contact dermatitis

Genotoxicity

Neurodevelopmental disorders

Hypersensitivity

Skin cancer

Neurotoxicity

Further individual preservative category reviewed from literature reveals the

following facts:

Benzalkonium Chloride: Benzalkonium chloride (BAC) and dimethyl

dioctadecyl ammonium bromide (DDAB) are quarternary ammonium compounds

used to prevent contamination due to bacterial growth in aqueous topical drugs,

opthalmics and nasal preparations and to preserve their pharmacological activities.

Its use in nasal preparations may cause nasal mucosal damage (Graf et al., 2001)

and it may cause damage to nasal epithelia and exacerbation of rhinitis

medicamentosa associated with intranasal products with BAC (Marple et al.,

2004). BAC is reported to be genotoxic to plant and mammalian cells and also

reported to cause genotoxicity and cytotoxicity from in-vitro study in which it

caused relevant DNA changes (Deutschle et al., 2006).

Thiomerosal: Eli Lilly developed thiomerosal in 1930s as an effective

preservative used in multidose vials, opthalmics, nasal and topical preparations

(Eke et al., 2008). Thiomerosal was a very common preservative being used

during the period from 1985 to 1997 and caused genetic depletion of glutathione

S- transferase which further caused the Kawasaki’s disease and also increased the

risk of acrodynia (Mutter et al., 2008). It was suggested to cause apoptosis in oral

cancer cells, gastric cancer cells and also cause cytotoxicity to human prostate

cancer cells (Liao et al., 2011). Thiomerosal may also cause neonatal

neurodevelopmental disorders and autism when used in childhood vaccines

(Berman et al., 2008). Further it is also reported to cause corneal opacification due

to thiomerosal induced toxicity in contact lenses (Nguyen et al., 2007).

Parabens: Parabens are alkyl esters of p-hydroxybenzoic acid and their various

derivatives, viz., methyparaben, ethylparaben, propylparaben, butylparaben,



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benzylparaben, isobutyl and isopropylparaben are widely used in many foods,

cosmetics and pharmaceuticals due to their relatively low toxicity (Tavares et al.,

2009). The use of parabens in cosmetic industry is very extensive such as in

deodorants, creams, lotions etc. The studies revealed that the use of parabens may

cause skin cancer, genotoxicity and breast cancer (Dabre et al., 2008). Parabens

are also reported to have side effects on males as it may decrease the reproduction

potential and cause infertility and may cause malignant melanoma and contact

eczema (Tavares et al., 2009; Lundov et al., 2009).

Polysorbates are a class of emulsifiers used in some pharmaceuticals and food

preparation. It is reported that polysorbates and benzalkonium were highly

cytotoxic with cell survival decreasing to 20% at the concentration estimated in

commercial ophthalmic solutions (Ayaki et al., 2008).

Benzyl alcohol is used as a general solvent for inks, paints, lacquers etc. It is also

a precursor to a variety of esters, used in the soap, perfume, and flavor industries.

It is often added to intravenous medication solutions as a preservative due to its

bacteriostatic and antipruritic properties. In vitro study on benzyl alcohol

cytotoxicity has significant clinical implications for intravitreal use of

triamcinolone acetate (Chang et al., 2008). Use of benzyl alcohol in triamcinolone

acetamide may cause retinal toxicity (Bitter et al., 2008).

Methyl paraoxy benzoate and propyl paraoxy benzoate may cause retinal

toxicity when used as preservatives in ophthalmic multidose formulations (Ayaki

et al., 2010).

Sodium benzoate and chlor acetamide are used in combination preservative in

cosmetics to prevent bacterial growth. In case of sorbolene lotion although it was

not clearly evidenced to cause allergic contact dermatitis but possibilities may be

there that they may cause some toxicity (Sutton et al., 2006).

Sulfites are often used as preservatives in various food and pharmaceuticals. An

in vitro study to confirm previous reports on dexamethasone and sulfite

neurotoxicity, and to investigate methylprednisolone, dopamine, and dobutamine

neurotoxicity was done and results showed that dexamethasone, soludecadron,

and sulfites increase neuronal cell death, while methylprednisolone and solu-

medrol are not neurotoxic, dopamine and dobutamine were found neurotoxic

independently from sulfite toxicity (Dani et al., 2007).

http://en.wikipedia.org/wiki/Emulsifier

http://en.wikipedia.org/wiki/Solvent

http://en.wikipedia.org/wiki/Ink

http://en.wikipedia.org/wiki/Paint

http://en.wikipedia.org/wiki/Lacquer

http://en.wikipedia.org/wiki/Soap

http://en.wikipedia.org/wiki/Perfume

http://en.wikipedia.org/w/index.php?title=Flavor_industry&action=edit&redlink=1

http://en.wikipedia.org/wiki/Bacteriostatic

http://en.wikipedia.org/wiki/Antipruritic

http://en.wikipedia.org/wiki/Preservative



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Methyl dibromo glutaronitrile and dibromo dicyano butane are commonly

used in cosmetic preparations as preservatives and have been reported that these

preservatives may cause contact allergy (Ramlogan et al., 2003; Torres et al.,

1992).

Further, a study done by Boukarim et al., (2009) revealed that the content of thirty

seven preparations were evaluated for their preservative content and 70 percent were

falling outside the typically allowed concentration, reason may be due to poor quality

control or also may be intentional so as to increase the shelf life of the product.

1.10 Possible alternatives to problems:

Alternatives to preservatives which are having toxic profile along with their potential

to kill microorganisms, is a challenge for researchers and development of new

preservatives is the target. Following alternatives are suggested to overcome the

problems associated with preservatives:

1.10.1 Use of novel preservatives:

Continuous research is going on to find out the preservative that is less toxic

and effective against the pathogenic microorganisms. Some of the

preservatives are being described as follows :

Polyquad : It is a high molecular weight compound used in contact lens

solutions and is effective in preventing growth of microbes especially fungi

and is well tolerated (Furrer et al., 2002).

Sodium perborate : It is catalyzed into hydrogen peroxide which further

converts enzymetically to water and oxygen and prevents microbial growth.

(Furrer et al., 2002)

Purite : It is a stabilised oxochloro complex which upon application in

presence of light is converted to water and sodium chloride (Bagnis et al.,

2011).

SofZia : It is a oxidative class of preservative composed of boric acid,

propylene glycol, sorbitol and zinc chloride that cause oxidative damage

followed with death of microorganism that lacks cytochrome oxidase and

catalase enzymes that covers most of the bacterias (Bagnis et al., 2011 ; Kaur

et al., 2009).

1.10.2 Non preserved single/unit dose products: The ocular delivery products

such as eye drops may be used in unit dose as the European



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Pharmacopoeia describes that the unit dose formulation to be used once

only so there may be the possiblity not to add preservative such as BAK

etc. (Furrer et al., 2002).

1.10.3 Non preserved multi dose products : The products that contains either

antibiotics or the alkaloids are having efficacy against microbes and

have no need of preservation but with specific storage conditions at low

temperature and for specific period of time after opening (Furrer et al.,

2002).

1.10.4 Packaging in speciallised containers : Containers that may contain the

microporous membrane in them with adsorbed preservative may be used

to store the sterile preparations. (Furrer et al., 2002; Bagnis et al., 2011)

1.10.5 Use of bacteriocins : Bacteriocins are antimicrobial proteins obtained

from bacteria and they kills/inhibit the growth of other bacterias. These

are ribosomally synthesized and usually kills closely related bacterias.

Antimicrobial peptides of LAB (Lactic acid bacteria) targets the

bacterias without toxic or adverse effects. Nisin is widely used as a food

preservative obtained from LAB. (Cleveland et al., 2001)

1.10.6 Use of natural preservatives: Natural preservatives may be used for

preservativation of food, cosmetic preparations etc. but their quantity to

be used is usually more and the associated constituents may cause other

side effects. So, a need of further research is there to explore the

potential of these naturally occuring agents. (Tiwari et al., 2009)

1.10.7 Synthesis of new derivatives from natural acids : The importance of

acids as antimicrobials is well established in the field of medicinal

chemistry. This makes them to be selected as potential candidates for

novel antimicrobial agents. The literature reports revealed that number

of organic acids from the natural sources (Table 9) are reported to have

antimicrobial activity in the last decade and have the scope for exploring

their antimicrobial potential. Natural acids from various common

sources such as rice, wheat, fruits etc. having promising antimicrobial

activities may be used to alter their chemical structure to get some novel

preservatives such as the derivatives of capryllic acid (Chaudhary et al.,

2008) and veratric acid (Ohlan et al., 2008).



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Table 9. Natural acids as antimicrobial agents.

S.No Natural Acid Activity reported References

1

Ferulic acid Antimicrobial, antioxidant,

anticancer, antiviral, anti-HIV

Landete et al., (2008)

Panizzi et al., (2002)

Stamatis et al.,(2001)

Stevenson et al.,

(2007)

2 Sinapic acid Antimicrobial, antioxidant

anticancer, anti-HIV

Tomas et al., (2000)

Stevenson et al.,

(2007)

3 Caffeic acid Antimicrobial, antioxidant


Cho et al., (1998)

Stevenson et al.,

(2007)

4 Gallic acid Antimicrobial and antioxidant Cho et al.,(1998)

Panizzi et al., (2002)

5 Ellagic acid Antimicrobial and anticancer Khallouki et al., (2007)

6 Protocatechuic acid Antimicrobial and antioxidant Landete et al., (2008)


7 Vanillic acid Antimicrobial and antioxidant Tomas et al., (2000)

8 Syringic acid Antimicrobial and antioxidant Landete et al., (2008)

Cho et al., (1998)

9 Cinnamic acid Antimicrobial, anti-malarial,

anticancer, anti-inflammatory

Said et al., (2004)

10 p- Hydroxy

benzoic acid

Antimicrobial and antioxidant Landete et al., (2004)


11 p- Coumaric acid Antimicrobial, antioxidant,


Feresin et al., (2003)

Stevenson et al.,

(2007)

12 Abetic acid Antimicrobial, cardiovascular,

antileishmanial, antioxidant,

antitumour, antiviral, anti

plateletlet activity

Barrero et al., (2004)

Feio et al.,(1999)

13 2-Hydroxypropane

-1,2,3-tricarboxylic

acid

Antimicrobial Lee et al., (2009)

14 Salicylic acid Antimicrobial and antioxidant Tomas et al., (2000)

Cho et al., (1998)



18

1.11. Conclusion:

Preservative is a very essential ingredient among the food and pharmaceutical

products as chances of contamination of such products is very high and their shelf

life becomes short. However, the preservatives which are used for this purpose may

pose several serious complications. For example, benzalkonium chloride may cause

nasal mucosal damage and is also reported to cause genotoxicity, thiomerosal may

cause neonatal neurodevelopmental disorders, use of parabens may cause skin

cancer, genotoxicity and breast cancer, etc. So, the use of preservatives becomes a

challenge and there is a strong need to overcome these problems by finding the

possible alternative to the existing preservation system. This includes the use of

novel preservatives such as polyquad, sodium perborate, purite, sofZia etc. or by

speciallized packaging or by developing new antimicrobial preservatives.

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