The search is on for paraben alternatives in cosmetics.
Phenylethyl alcohol ([C.sub.8][H.sub.10]O) is found in fruits and flowers such as rose, banana, apple and lily. It has a floral odor with a rose character. In cosmetics, it can be used as a fragrance and deodorant. It has antimicrobial activity, especially against gram-negative bacteria and fungi. In pharmaceuticals, it serves as a fragrance, flavoring agent and as a preservative in ophthalmic solutions. Caprylyl glycol ([C.sub.8][H.sub.18][O.sub.2]) is a linear diol that acts as a skin humectant, wetting agent and solubilizer. It gives a pleasant skin-feel and has antimicrobial properties.
Apparently, the combination of the two actives shows a synergistic antimicrobial effect as the wetting ability of the glycol may enhance the intracellular penetration of the alcohol, which inhibits cellular processes and macromolecular synthesis.
Stabil is very stable in glycerine, propylene glycol and ethanol. Up to 5% can be added in mineral oil, but only 0.6% in water. It is stable and effective in the pH range of 4-8, but the best activity is obtained in acid pHs.
The activity of Stabil was determined by running Minimum Inhibitory Concentration (MIC) and Minimum Biocidal Concentration (MBC) tests using the following organisms: gram-positive bacteria (S. aureus), gram-negative bacteria (E. coli and P. aeruginosa), yeast (C. albicans) and mold (A. niger).
The tests were run with and without disodium EDTA chelating agent. It was discovered that disodium EDTA enhanced the antimicrobial effectiveness of Stabil, resulting in a big reduction of MIC and MBC values, and allowing for lower levels of Stabil to be used. The same five microorganisms listed above were added to cosmetic formulas and checked for microbial growth initially and after 2, 7, 14, 21 and 28 days. One of the test formulas was the following:
O/W Emulsion with a Nonionic Emulsifier Ingredients: %Wt. PEG-100 stearate, 5.0 glyceryl stearate Octyl octanoate 4.0 Glycerine 4.0 Paraffinium liquid 3.0 Caprylic/capric triglyceride 3.0 Cetyl alcohol 2.0 Dimethicone 0.5 Allantoin 0.5 Carbomer 0.2 Disodium EDTA 0.1 Sodium hydroxide (10%) q.s. Water 77.7 Stabil 0.8
The above formula was also made with no preservative and with 1% Stabil. The results showed that both Stabil concentrations totally inactivated the gram-negative bacteria (E. coli and P. aeruginosa) within two days. The 0.8% formula inactivated the S. aureus in 7 days, the C. albicans in 14 days, but it took 28 days to control the A. niger. The 1% Stabil was better. All of the organisms were killed within seven days.
Other formulas were tested with similar (but not exactly the same) results. The A. niger mold took from 1-1.2% Stabil (depending upon the formula) to kill within seven days. Up to 1.5% is recommended for formulas which are more susceptible to molds.
Some formulating tips include adding it to an emulsion after it has been formed at a temperature of 60[degrees]C or less. It can be dissolved in surfactants in a shampoo, without heating, before adding the other ingredients. Alcohols or glycols will help solubilize it in an aqueous solution to its limit of 0.6%. The use of chelating agents is always suggested to improve the antimicrobial efficacy of Stabil.
Some companies insist on marketing their products as preservative-free. But if a product contains Stabil or another non-traditional preservative, the claim, "self-preserving," would be a more accurate description.
HARVEY FISHMAN HAS A CONSULTING FIRM AT 34 CHICASAW DRIVE, OAKLAND, NJ 07436, HRFISHMAN@MSN.COM, SPECIALIZING IN COSMETIC FORMULATIONS AND NEW PRODUCT IDEAS, OFFERING TESTED FINISHED PRODUCTS. HE HAS MORE THAN 30 YEARS OF EXPERIENCE AND HAS BEEN DIRECTOR OF RESEARCH AT BONAT, NESTLE LEMUR AND TURNER HALL. HE WELCOMES DESCRIPTIVE LITERATURE FROM SUPPLIERS AND BENCH CHEMISTS AND OTHERS IN THE FIELD.
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|Title Annotation:||Gleams & Notions|
|Publication:||Household & Personal Products Industry|
|Date:||Mar 1, 2007|
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