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v_singh

Demonstrating effects of zinc PCA

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I found the info randomly while surfin tha web ... duno if its usefull or not i havnt really read it but its about sebum production etc.

Demonstrating effects of zinc PCA

November 2006

Naoko Mikami and Naoya Yamato - Ajinomoto Co Inc, Japan In recent years, there has been a growing demand for a means to suppress sebum secretion and keep skin clean in young people, and exert anti-ageing effects in adults, as well as to suppress body odour in people of all ages.

Zinc compounds have been reported to be effective as sebum inhibitors, odour absorbers, and so on. We have recently shown that zinc PCA can produce these effects and also inhibit AP-1 – a promoter of collagenase production, which is responsible for the appearance of skin wrinkles.

In this study we demonstrate the effects of zinc PCA; namely, sebum inhibition, inhibition of bacterial growth and suppression of AP-1. Ajidew ZN-100 is a brand name of Ajinomoto Company Inc. for zinc PCA.

What is zinc?

Zinc is one of the essential trace elements for any living body.1 Fish and shellfish are naturally rich in zinc. Zinc deficiency in humans is unlikely to occur with a balanced diet. However, an unbalanced diet is known to cause dysgeusia, reproductive dysfunction, skin roughness, hair loss and so on. In elderly people, similar unbalanced diets can lead to a compromised immune function.2

In the field of cosmetic and toiletry products, zinc is known to form nonvolatile salts with fatty acids and other substances, and exert antibacterial activity. Zinc is also used as an ingredient of baby powders, shaving powders, anhidrotic agents, creams and so on.

Sebum inhibiting activity

Dihydrotestosterone (DHT), a metabolic product of testosterone, produced by the action of the enzyme 5 a-reductase, stimulates sebaceous glands to produce and secrete sebum. Zinc inhibits 5 a-reductase activity.4,5

Odour-absorbing activity

If zinc forms salts with short-chain fatty acids that cause body odour, the characteristic odour disappears as shown in Figure 3. In this connection, zinc PCA, which is a zinc compound, is expected to suppress body odour by forming nonvolatile salts with short-chain fatty acids in the skin.6

What is zinc PCA?

As described above, zinc inhibits sebum secretion and body odour. However, the solubility of zinc salts is usually low, making it difficult to add zinc compounds to cosmetics, and difficult for the effects of zinc compounds to manifest. We paid close attention to pyrrolidone carboxylic acid (PCA), which is an organic acid, as a counter for the formation of zinc salts, and evaluated its functions.

PCA is the predominant component of NMF (Natural Moisturising Factor) and is known to play important roles. PCA originates from glutamic acid abundantly contained in the living body. Glutamic acid, which is biosynthesised by hydrolysis of filaggrin (a protein) during the course of skin keratinisation, is hydrolysed and cyclised with skin enzymes (g-glutamyl-AA synthetase and g-glutamyl cyclotransferase),7 to yield PCA. Usually, PCA is found in the skin in the form of salts (Na salt, K salt, etc.) and it is abundantly contained in NMF.8 PCA, assuming the form of salt, is known to serve as a moisturiser which keeps the skin soft and to exert excellent conditioning effects on the hair.

Characteristics

The following effects of zinc PCA have been confirmed in our study:

Reduction of unwanted sebum.

Inhibition of activator protein-1 production.

In addition, effects on microorganisms were measured.

Reduction of unwanted Sebum

Zinc PCA gives freshness to the skin. Figure 6 shows changes in skin sebum level observed after repeated applications. One per cent zinc PCA solution has been shown to significantly decrease sebum levels on the treated skin at week four, compared to initial value. On the other hand, treatment with water or zinc gluconate does not result in any significant difference to initial value. These results suggest that zinc PCA can be expected to show a promising effect as cosmetic for oily skin.

Procedure

The subjects were asked to apply 1% zinc PCA solution, 1% zinc gluconate and water to the one side of the face, morning and evening, for four weeks. Secreted sebum was measured by sebumeter measurements (SM 810 PC, Courage and Khazaka, Electronic GmbH) and the measurement on the treated skin after three hours and four weeks was expressed as a ration of the initial value (before the treatment). All the subjects were required to complete a 30-minute acclimation period in the environmental chamber (22°C, 40% relative humidity), where all sebum measurements were taken.

Results

By application of zinc PCA, statistically significant decrease of the sebum content from the initial value was observed.

Inhibition of activator protein-1

Collagen, which is indispensable for keeping the skin tense and to prevent wrinkle formation, is degraded by collagenase (an enzyme that degrades collagen). Therefore, to suppress wrinkle formation, it is necessary to suppress collagenase production.

It is known that activator protein-1 (AP-1 – a complex protein composed of a few protein units, produced by stimuli such as UV radiation) induces the production of collagenase by binding to DNA in the cell nucleus. This means that AP-1 formation needs to be suppressed to inhibit collagenase production (Fig. 7). We therefore evaluated the effect of zinc PCA in suppressing the production of AP-1. This experiment revealed that treatment with even low levels of this substance suppressed c-FOS (an indicator of AP-1 production) by about 70%. This result suggests that zinc PCA can suppress wrinkle formation.

Mechanism of collagen degradation and wrinkle formation

Procedure

Zinc PCA was added to human fibroblasts and the cells were irradiated with UVA. After the irradiation, the amount of c-FOS (a component of AP-1) was determined.

Calculation method

A: zinc PCA (+), UVA irradiation (+) B: zinc PCA (-), UVA irradiation (+) C: zinc PCA (-), UVA irradiation (-) c-FOS Production inhibition (%) = {1-(A-C)/(B-C)} x 10.

Results (Table 2).

Minimum Inhibitory Concentration (MIC)

Procedure

Agar medium containing zinc PCA at different concentrations was prepared and dispensed on culture plates. Each organism suspended in culture medium was seeded on the agar plate. After incubation, the minimum inhibitory concentration (MIC) was determined. MIC is the lowest concentration on microorganisms for which there is no visible growth. (Agar plate dilution method) *The concentration indicates that of zinc PCA itself.

Results (Table 3).

Challenge test for zinc PCA

Preservatives-effectiveness tests were performed on 0.1% zinc PCA aqueous solution.

The following strains were used as the test microorganisms.

Escherichia coli ATCC 8739

Pseudomonas aeruginosa ATCC 9027

Staphylococcus aureus ATCC 6538

Candida albicans ATCC 10231

Aspergillus niger ATCC 1644

The cell suspension was inoculated and mixed so that the concentration of viable cells was 105 to 106 cells per ml of product. These containers were incubated at 25°C and the viable cell counts calculated at 7, 14, 21, and 28 days.

Results (Fig. 8).

Formulation

Zinc PCA is expected to be useful not only in ordinary skin care but also to exert the above-mentioned effects more markedly if combined with shampoos, conditioners, and body and facial cleansers.

Augmentation of its effects is expected if the shampoos or conditioners containing this substance are used in combination with other antibacterial agents or anti-acne products (containing zinc pyrithione, piroctone olamine and so on). If combined with substances known to stimulate hair growth (amino acids, blood flow promoting agents (PCA, vitamin E and other various extracts), more efficacy in stimulating hair growth is expected. As stated above, the effect in suppressing AP-1, etc is expected to be augmented if this substance is combined with elements having an anti-oxidative activity (known as antiwrinkle agents).

Application

Skin care: creams, lotions, tonics, shower gels, facial cleanser, etc.

Hair care: shampoos, conditioners, hair tonics, hair creams, etc.

Sun care: pre and post sun care creams, lotions, gels, etc.

Make-up: foundations, lipsticks, etc.

Recommended concentration

Leave-on products: 0.1 ~ 1.0% Rinse-off products: 0.2 ~ 1.0% (as active ingredient)

Conclusion

It has been shown that zinc PCA exerts not only the effects expected from a Zn salt (sebum suppression, body odour reduction, etc.) but also some previously unknown effects (AP-1 inhibition effect, etc). Humans tend to be anxious about oil-producing and odourous areas of the body, even as they get older, and they are highly concerned about skin wrinkles, which increase with ageing. Zinc PCA is expected to be used extensively not only as a means of suppressing sebum and body odour, but also as an ingredient for anti-ageing products.

This information is furnished without warranty, expressed or implied, except that it is accurate to the best knowledge of AJINOMOTO CO. INC. It relates only to the specific material designated herein, and does not relate to use in combination with any other material or in any process. AJINOMOTO CO. INC. assumes no legal responsibility for use of or reliance upon this.

References

1 K., Imahori et al., Seikagakujiten (Biochemical Dictionary), Tokyo Kagaku Dozin, 3 (1987)

2 Y. Kagawa, Standard Tabels of Food Composition in Japan, 371 (2004)

3 Encyclopedia of Cosmetics (ed. Society of Cosmetic Chemists of Japan), 306 (2003)

4 D. Stamatiadis, Marie-Claire Bulteau-Portois and Irene Mowszowicz, British Journal of Dermatology, 119, 627-632 (1988)

5 Yasuro Sugimoto, Irma Lopez-Solache, Fernand Labrie and Van Luu-The, Journal of Investigative Dermatology, 104, 775-778 (1995)

6 Mitsui T, New Cosmetic Science, Elsevier, 467 (1997)

7 P. G. Crounse & S. Rothberg (1961)

8 H.W. Spier, G. Pasher, Hautarzt, 7(12), 1956

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