An Overview of Preservatives and their Modes of Action

Transcription

1 An Overview of Preservatives and their Modes of Action Kevin Roden Thor Specialties What is a Preservative? A substance that maintains (preserves) the original performance/characteristics/integrity of the product by controlling the growth of contaminating microbes Chemical agents added to products to prevent the growth of microorganisms protect the product from microorganisms added to the product during use to stop organisms growing, not to treat contaminated material or to make up for poor production methods Also physical means, water activity, ph, packaging will not be discussed 1

2 Preservation - Disinfection without preservation insufficient preservation Cell count Microbiostasis disinfection sufficient preservation time Australian Regulations Preservatives for use in cosmetics in Australia are regulated by several means: NICNAS AICS Cosmetic guidelines ACCC Cosmetic regulations TGA SUSMP 2

3 EU Cosmetics Regulation Annex V The preamble to Cosmetics Directive Annex VI stated: 1. Preservatives are substances which may be added to cosmetic products for the primary purpose of inhibiting the development of micro-organisms in such products. 3. Other substances used in the formulation of cosmetic products may also have anti-microbial properties and thus help in the preservation of the products, as, for instance, many essential oils and some alcohols. These substances are not included in this Annex. Cosmetic Ingredients which may assist Preservative Efficacy Alcohols Glycols, sugars Cationic surfactants Chelating agents Potentiators Control water availability Affect integrity of microbial cell membrane Interfere with Gm negative bacterial outer membrane by binding Mg 2+ & Ca 2+ Natural (essential oils) Exhibit selective anti-microbial activity Acids/alkalis Fatty acid esters Reduce spectrum of microbial activity through ph control Exhibit selective anti-microbial activity 3

4 EU Cosmetics Regulation Annex V The preamble to Cosmetic Directive Annex VI stated: 1. Preservatives are substances which may be added to cosmetic products for the primary purpose of inhibiting the development of micro-organisms in such products. 3. Other substances used in the formulation of cosmetic products may also have anti-microbial properties and thus help in the preservation of the products, as, for instance, many essential oils and some alcohols. These substances are not included in this Annex. The EU regulations Annex V definition is: Preservatives mean substances which are exclusively or mainly intended to inhibit the development of micro-organisms in the cosmetic product Commonly used preservatives Benzoic acid Propionic acid Salicylic acid Dehydroacetic acid sorbic acid formaldehyd e MIT/CIT DMDM Hydantoin Methyl isothiazolinone Diazolidinyl urea parabens phenoxyethanol Benzyl alcohol Undecylenic acid hexetidine Sodium hydroxymethyl glycinate bronopol chlorphenesin IPBC Bromo-nitrodioxane Polyaminopropyl biguanide Formic acid Imidazolidinyl urea hexamidine Dichlorobenzyl alcohol trichlocarban chlorocresol triclosan chloroxylenol methanamine OPP Zinc pyrithione Sodium Quaternium-15 climbazole sulphite Benzalkonium chloride Ethyl lauroyl arginate HCl Piroctone olamine Bromo chlorophene Isopropylcresol phenylmercuric chlorophene chloracetamide Benzylhemiformal Phenoxy isopropanol Cetrimonium chloride Dimethyl oxazoladine chlorobutanol Ethylbicyclo oxazolidine Benzethonium chloride Chlorhexadine thiomerosal Silver chloride Dibromohexamidine glutaraldehyde 4

5 Regulation: EU Substance Maximum concentration (%) Potassium sorbate 0.6% (acid) Parabens Methyl, ethyl, propyl, butyl 0.4% individual, 0.8% total (as acid) Dehydroacetic acid 0.6% (acid) Phenoxyethanol 1.0% Benzyl alcohol 1.0% CIT/MIT 1: % Chlorphenesin 0.3% MIT 0.01% Substance Rinse off Leave on Other Sodium benzoate 2.5% (acid) 0.5% (acid) 1.7% oral (acid) IPBC 0.02% 0.01% % deodorant Not to be used for lip or oral, not for children under 3 years except rinse off Not for products applied to large part of the body Biocides Mode of Action Biocide Formaldehyde Bronopol Isothiazolinone Imidazolidinyl urea Mercurials Hexamine Derivatives Parabens Formaldehyde Hexamine Derivatives Quaternary Ammonium Compounds (QAC s) Alcohols Mode of Action Oxidation of thiol groups and inhibition of sulphydryl groups in cytoplasmic membrane and intracellular enzymes Transmembrane ph gradient effecting Proton transfer across the cell wall and cytoplasmic membrane Amino groups in the cytoplasm Including proteins, DNA, RNA Potassium, Ribosome leakage through cell wall 5

6 Effects of Preservatives Disruption of the transmembrane proton motive force leading to uncoupling of oxidative phosphorylation and inhibit active transport across membrane Inhibition of respiration or catabolic/anabolic reactions Disrupt replication Lose membrane integrity Lysis Coagulation of intracellular components Effects Metabolic imbalance after sublethal injury may lead to free radical production and self destruction Differentiates highly metabolising exponential growth cells from those in stationary phase. Stationary phase Decline phase Log10 Cell Count Log phase Lag phase Time 6

7 Preservative Actives Commonly used preservatives Methylparaben methylparaben methylparaben methylparaben propylparaben propylparaben propylparaben propylparaben Imidazolidinyl urea butylparaben phenoxyethanol phenoxyethanol butylparaben ethylparaben butylparaben butylparaben ethylparaben phenoxyethanol ethylparaben ethylparaben phenoxyethanol Christmas pictures Imidazolidinyl urea isobutylparaben Isobutylparaben DMDMH DMDMH isobutylparaben MI MI/MCI MI/CMI MI MI/CMI Quaternium 15 Diazolidinyl urea MI/CMI DMDMH USA Canada Caprylol glycol Pentylene glycol

8 Paraben esters methyl, ethyl, propyl, butyl, isobutyl Chemical Type: Phenolics, Esters of parahydroxybenzoic acid (para acid). O Spectrum of Activity: HO C OCH Fungi & Gram positive bacteria 3 They are inactivated by strong hydrogen bonders such as ethoxylated compounds, cellulose gums, lecithin. Incompatible with some nonionics World wide approval for use Effective across ph 4 8 Since April 2014 Paraben Maximum concentrations (as acid) Methyl, Ethyl, Propyl, Butyl 0.4% for one ester 0.8% for esters blend Isobutyl, isopropyl, phenyl Risk can not be evaluated due to lack of data Increase in chain length gives increase in activity and decrease in water solubility Methyl paraben HO O C OCH 3 Ethyl paraben Propyl paraben Paraben esters methyl, ethyl, propyl, butyl Butyl paraben Paraben Water (w/w 25 O C) Water (w/w 80 O C) Ethanol (w/w) MIC Ps. aeruginosa Methyl Ethyl Propyl Butyl

9 Parabens Bad press regarding breast cancer and hormone mimic has resulted in reduced usage. Japanese Study suggests that under influence of UV light Methyl paraben increases skin aging no claims proven Benzyl Alcohol Chemical Type: Phenolic like Spectrum of Activity: active against Gram positive bacteria, but is weak against mould. It acts more as a bacteriostat Characteristic: Volatile and may be inactivated by nonionics should be used with an antioxidant and <ph 7 Listed in EU as a fragrance allergen Typical Dose (%) : Maximum dose: 1% Used in combination with other actives at relatively high concentrations 9

10 Phenethyl alcohol Found in nature in a variety of essential oils Colourless liquid with warm rose and honey aroma Better activity than benzyl alcohol Non volatile Not a listed preservative Used in combination with other actives at relatively high concentrations Usually mixed with caprylyl glycol or phenoxyethanol Although phenethyl alcohol is known for its antimicrobial properties, it s not on EU, Japanese or the U.S. list of recognized cosmetic preservatives and so theoretically this system can be considered a preservative-free preservative, added Ms. Kasprzyk Phenoxyethanol Chemical Type: Phenolic like Spectrum of Activity: Some activity against bacteria, yeast and moulds, especially Gram ve bacteria (Pseudomonas sp.) Characteristic: Good solvent for parabens and some other preservatives. World wide approval for use Wide ph range 3 10 May be inactivated by nonionics. Typical Dose (%) : Maximum dose: 1% Used in combination with other actives at relatively high concentrations 10

11 MIC Values (ppm) Mixture St.aureus Ps. aeruginosa C. albicans phenoxyethanol phenethyl alcohol % phenoxyethanol 30% phenethyl alcohol 69% phenoxyethanol 30% phenethyl alcohol 1% lactic acid > Lactic acid >100,000 Alcohols enhance the permeability of micro-organisms and causes disruption of the cell membrane. The destabilization of the membrane permeability barrier allows the entry of materials that are normally unable to penetrate the cell. It also allows the loss of important cell components that lead to the inhibition of DNA synthesis. Formaldehyde Preservatives Formaldehyde/formalin O CH 2 Formaldehyde releasers H 2 C CH 2 HO CH 2 O O CH 2 Formaldehyde is listed in Annex V with a maximum use concentration of 0.2%, but is limited to 0.1% in oral products and prohibited from use in aerosols. Products with >0.5% formaldehyde must be labelled Contains formaldehyde. 11

12 Formaldehyde Releasers Advantages : Fast acting Broad spectrum against bacteria Sporicidal Can give headspace protection Activity unaffected by ph Low cost Disadvantages : Odour Perceived toxicity; carcinogen, sensitiser, irritant Poor efficacy against moulds and yeasts Head Space Protection HCHO HCHO Full Jar Used Jar 12

13 Formaldehyde Donors HCHO Donor Imidazolidinyl urea Diazolidinyl urea DMDM Hydantoin Activity spectrum Gram +ve Gram ve No fungi Gram +ve Gram -ve Some Fungi Gram +ve Gram ve Weak Fungi Typical Stability Use conc (%) C ph C ph C ph 3-10 Max level HCHO biocide/ product 0.6% a) 31 b) % a) 43 b) % a) 33 b) Sodium hydroxymethyl glycinate Gram +ve Gram ve Some fungi Weak yeast C ph % a) 24 b) a) % total formaldehyde bound in biocide based on 100% active b) % free formaldehyde released into cosmetic at maximum addition level of active ECHA Chemicals for substitution 13

14 The effect of ph on organic acids Organic Acids Concentration (%) of organic acid in undissociated state Water Organic acid ph5 ph6 ph7 solubility Salicylic acid Benzoic acid (sodium benzoate) 13 1,5 0, Sorbic acid (Potassium sorbate) Propionic acid miscible Dehydroacetic acid <0.1 Organic acid pka Salicylic acid 3.0 Formic acid 3.8 Benzoic acid 4.2 Sorbic acid 4.8 Propionic acid 4.9 Dehydroacetic acid 5.4 Propyl paraben 8.1 Methyl paraben 8.5 Boric acid 9.1 The activity is ph dependent, efficacy in a very narrow ph range around their pk a values. ph Range Undissociated state enables the uncharged acid to pass through the negatively charged cell Typical use rates are % Recommend to add organic acid in water for emulsion system. Microbes exist in water phase. Preservatives also must be in water phase. If added in oil phase, undissociated form may stay in oil phase. Organic Acids mode of action R-COO - Na + R-COO - Na + R-COO - H Cell R-COO - Na + R-COO - Na + H + ATP level R-COO - H R-CO R-COO - Na + Na + Na + R-COO - Na + R-COO - H R-COO - H R-COO - Na + The cell will actively try to restore its optimal ph by exchanging H + ions by Na + ions. To do this it will use its energy source the ATP Use in combination with active transport inhibitors for greater effect 28 14

15 MIC values Extract St. aureus Ps. aeruginosa C. albicans Lactic acid ,000 Citric acid ,000 Anisic acid Levulinic acid/sodium levulinate >10000 >10000 >10000 Lactic Citric Anisic Levulinic sample 10% 5% 2.5% 1.25% 0.68% 0.34% 0.17% 0.09% 0.05% pk A anisic grow 4.47 Lactic grow 3.86 Citric grow 3.08 Levulinic 4.5 Case Study Baby moisturising cream ph 5.0; preserved with 1% Microcare SB Potassium sorbate plus sodium benzoate Pass Preservative Efficacy Test, production contaminated At ph 5 sorbic acid (pka 4.8) only 37% activity benzoic acid (pka 4.2) only 13% activity Factory hygiene very important to stop development of tolerant organisms Action Lower ph to 4.7, increased Microcare SB to 1.2% Sorbic acid from 37% to 80% active Benzoic acid from 13% to 35% active Small increase in preservative and small drop in ph achieve 300% increase in the preservation strength No contamination in production 15

16 Halogenated Compounds Methylchloroisothiazolinone (MCI) Methylisothiazolinone (MI) Bronopol Methyl dibromo gluteronitrile Iodopropynyl Butylcarbamate (IPBC) Chlorophenesin methylchloroisothiazolinone/methylisothiazolinone (MCI/MI) mix 3:1 Chemical Type: Halogenated Compounds N-CH 3 S Spectrum of Activity: Cl Excellent broad spectrum activity against all bacteria and fungi Characteristics MCIT: Water soluble Poor stability above ph7 in presence of amines such as coco-dea and inactivated by zinc pyrithione Skin sensitiser, restricted to15ppm in rinse off and leave-on products Compatible with all types of surfactants. SCCS opinion released: safe at 15ppm for rinse off, not to be used in combination with MIT O + O N-CH 3 S 16

17 Methylisothiazolinone (MI) Chemical Type: O Heterocyclic N, S Compounds Spectrum of Activity: S N CH 3 broad spectrum activity against bacteria, poor fungicide Characteristics: Miscible with water, propylene glycol and lower alcohols Lower sensitisation than CIT/MIT (~30X) May be used for leave-on applications Compatible with all types of surfactants. Effective alternative to formaldehyde donors Excellent inherent stability over wide ph and temperature range Typical Dose (%) : 0.01 Maximum allowed concentration 100ppm Tricarboxylic acid cycle Malate dehydrogenase Fumerase Malate Pyruvate CO 2 Acetyl-coenzyme A Citric synthase Citrate Oxalacetate Pyruvate dehydrogenase Aconitase Cis-aconitate Aconitase Isocitrate Isocitrate dehydrogenase Fumerate Succinate dehydrogenase Succinate Succinyl-coenzyme A Succinyl kinase CO 2 CO 2 Ketogluterate Ketogluterate dehydrogenase 17

18 Enzyme Active Site Effect of isothiazolinones Tricarboxylic acid cycle Malate dehydrogenase Pyruvate Pyruvate dehydrogenase Acetyl-coenzyme A Citrate Oxalacetate Cis-aconitate Malate Isocitrate Fumerate Succinate dehydrogenase Succinate Succinyl-coenzyme A Ketogluterate Ketogluterate dehydrogenase 18

19 Electron transport chain Oxidative phosphorylation AH 2 A Carrier I OX Carrier I RED ADP ATP Carrier II RED Carrier II OX Produces large amounts of ATP Transports protons across cell membrane Interior alkaline and negatively charged ADP Carrier III OX H 2 O Terminal oxidase Carrier III RED 1/2 O 2 ATP CIT association occurs in minutes ug CIT per mg protein P. aerug. 1 P. aerug. 2 P. florec Minutes 19

20 IodoPropinylButylCarbamate (IPBC) Chemical Type: Halogenated Compounds Spectrum of Activity: Fungal only Characteristics: hydrolysis in strong alkaline conditions Heat stable to 40 0 C Typical Dose (%) : % Maximum allowed concentration; rinse off products 0.02% leave on products 0.01% deodorants/antiperspirants % Not allowed in oral or lip products, children cosmetics or body lotions Chlorphenesin Listed preservative Fungicide Coming into favour with loss of parabens and IPBC Used in combination with other preservatives like phenoxyethanol 20

21 Efficacy Comparative MICs Preservative Pseudomonas aeruginosa Sources: Thor data, trade & technical literature MIC (ppm) Staphylococcus aureus Aspergillus brasiliensis Candida albicans MCI/MI MI Bronopol Formaldehyde DMDMH Diazodinyl urea >6000 IPBC Chlorphenesin Phenoxyethanol Methyl paraben Caprylyl glycol Decylene glycol Combinations of Actives Why? Broader Activity Ease of Incorporation Increased stability Dilution of Actives 21

22 Combination Preservatives MCIT/MIT & Benzyl Alcohol Diazolidinyl urea or Imidazolidinyl urea & methyl and propyl paraben Methyl, ethyl and propyl parabens & phenoxyethanol Methyl, ethyl, propyl, butyl and isobutyl parabens & phenoxyethanol MCIT/MIT & Formaldehyde MCIT/MIT & Bronopol MIT & lots Preservative mixtures Preservative Phenoxyethanol & organic acids Phenoxyethanol & glycols Phenoxyethanol & phenols Phenoxyethanol & everything (extracts) Glycols & organic acids Sodium benzoate & potassioum sorbate Benzyl alcohol & dehydroacetic acid Preservative free Glycols Glycols & phenols Glycols & caprylates Glycols & everything (extracts) 22

23 What s wrong with preservatives Active Parabens Formaldehyde and donors Bronopol MI MI/MCI IPBC Triclosan Synthetic preservatives Concern Cancer, hormone mimic Cancer, sensitiser Nitrosamine, formaldehyde Sensitiser Sensitiser Sensitiser, Iodine Everything bad Toxic Marketing 23

24 Natural Product Citramed Citrazole Plantservative Natacide Biosecure A520D Leucidal liquid Phytocide Elderberry Grape fruit seed extract Content Grapefruit peel extract Citrus extract Lonicera caprifolium & japonica extract Vegetable extract, vanilla and almond odour Hydro-glycerin Citrus extract, no grapefruit Leuconostic fermentation of Radish root Elderberry fruit extract Grapefruit pulp Chemical structure of 1,2-alkanediols 1,2-alkanediols Isomers etc C2: 1,2 ethanediol C3: 1,2 propanediol HO 1,2,3 propane triol (glycerin) C4: 1,2 butanediol 1,3 butane diol C5: 1,2 pentanediol C6: 1,2 hexanediol HO 1,5 pentane diol 2,4 pentane diol C8: 1,2 octanediol (Caplyryl glycol) O Di propylene glycol C10: 1,2 decanediol HO O O H n PEG 24

25 Membrane inhibition Model of 1,2-alkanediol Substances outside of cell Outer 1,5-pentanediol 1,2-diol Lipid bilayer Inner phospholipids Substances inside of cell (K +, ribosomes) Efficacy and Skin irritation potential Thor recommendation ppm 40,000 35,000 30, % needed 2.5% needed S. aureus E.coli Ps. aeruginosa C. albicans A. niger 25,000 20, % MAX 15, % MAX 10,000 5, % MAX 0.25% needed 0.3% MAX 0.06% needed - PTG C5 HXD C6 CLG C8 DCG C10 Blue box: highest MIC minimum required concentration Green box: Thor recommendation of maximum dosage from risk assessment (NOAEL, MoS) 25

26 1,2- alkanediol Migration Model of 1,2-alkanediol Alkane diols more soluble in polar oil phase, > solubility in caprylic/capric triglyceride than in mineral oil Reduce polarity of oil phase or add solvent to water phase Increase emulsifier concentration or use mixture of ionic and nonionic Aqueous phase Oil phase Caprylic acid Other actives Glyceryl capralate Caprylhydroxamic acid Sorbitan caprylate 26

27 Preservative Selection critical that the preservative selected for a product is matched to the physical and chemical requirements of the product and will provide protection against the full spectrum of microorganisms likely to be encountered. The preservative must be used correctly Addition point Concentration ph, temperature, surfactants, water/oil phases The toxicity, or the perceived toxicity of the active must also be compatible with the intended use and market. Basing the selection of preservative actives on these criteria and ensuring good manufacturing practices should enable production of Personal Care Products with no fear of contamination or adverse effects Antidandruff shampoo 1% zinc pyrithione Sodium benzoate Benzyl alcohol Methylchloroisothiazolinone Methylisothiazolinone ph 5.87 Sodium benzoate inactive but high solubility Convert to benzoic acid above pka Useful at ph <4.7, pka 4.2 Mainly antifungal activity, low antibacterial activity Suggested Preservative: Methyl Isothiazolinone Now: reduce the ph and use benzoic acid/sorbic acid % Zinc pyrithione 10,000ppm no ZPT 1% ZPT MIC for: St.a 4ppm Ps.a 512ppm ZPT solubility in water 8ppm Mainly antifungal activity, low antibacterial activity 0 2 days 4 days 6 days 8 days 10 days methylchloroisothiazolinone degraded by free pyrithione will give initial preservation methylisothiazolinone Present at 4ppm Need higher concentration 27

28 Get the Balance Wrong Batch Numbers: Sold: Defect: Hazard: Defect: Hazard: What to do: Contact Details: 28