Antioxidant Efficacy

Published: 30-Oct-2012

A non-invasive method to evaluate the persistence of antioxidant protection provided by the application of an active cosmetic composition, in realistic conditions.

Kinetic follow-up of the antioxidant capacity of a care product applied to the skin;



A non-invasive method to evaluate the persistence of antioxidant protection provided by the application of an active cosmetic composition, in realistic conditions.

[Summary of the article published in Les Nouvelles Dermatologiques (2011 ; 30 : 477-480)]


Christophe COURBIERE, Efficacy Clinical Studies Manager - IDEA
Dominique OSTINET, In Vitro Studies Manager - IDEA
Erica MENNESSON, Quality, Regulation & Objectification Manager - Laboratoire NUXE
Virginie LE NOEL, Objectification Manager - Laboratoire NUXE
Mélissa MIGNARD, Dermatologist, Eurotox Expert (clinical toxicology) - IDEA

The main objective of the study was to compare a natural antioxidant polyphenol complex with vitamin E (tocopherol), one of the reference antioxidant agents. These 2 agents have been evaluated as a finished product, incorporated into the same vehicle (H/E emulsion), and compared to a placebo.

The principle of the method consisted in applying on the skin the products to be compared into standardized conditions, then taking, at various times after application, samples of the surface of the Stratum Corneum (SC ) using adhesive strips D-Squame® (CuDerm Corp. Dallas, TX, USA). Antioxidant activity was then measured on the strips, allowing a comparison between the efficacy of the products at various sampling times.


Survey Process

This single-centre, open-label, comparative, randomized survey has been conducted on a panel of 26 adult female volunteers, with a mean age of 45.9 years old, between 18 and 60 years old.

These volunteers had no skin damage on the area being studied, no allergy history to any cosmetic products, and signed an informed and express consent form.

The survey was carried out under controlled temperature and humidity conditions. The products were applied in accordance with the randomization plan, at a ratio of 2 mg/cm2, on the inner surface of the forearms, where 4 square areas with sides of 5 cm were delimited: 3 were treated and 1 remained untreated, serving as a control area. 15 minutes, 4 hours and 8 hours after the end of application, a D-Squame® adhesive was placed on each area and kept in contact with the skin in standardized conditions to sample the SC.

The measurements of antioxidant activity were taken by placing the strips in contact with the reagent: of a methanolic (2.2-diphenyl-1-picrylhydrazyl ) DPPH solution at 60 μmol/l.

The negative control was performed on a fresh D-Squame® adhesive in the presence of the same volume of methanolic DPPH solution.

The strips in the presence of the DPPH solution were then incubated at room temperature away from light.

After incubation, the absorbency was measured at 540 nm with a Thermo® Multiscan EX® spectrophotometer.


Results :
Kinetic of the antioxidant activity 15mn, 4 hours and 8 hours after products application

Antioxidant Efficacy

The absorbency values obtained on the 3 treated areas were compared with those obtained on the untreated control area.

The formula containing the polyphenol complex showed a significantly higher antioxidant activity than that of the product containing vitamin E, and than the inactive placebo.

In order to facilitate comparisons, the results were expressed as a percentage increase in antioxidant activity compared to the control area that received no product.


Conclusion:

The proposed method is a non-invasive way of differentiating formulations regarding their antioxidant activity on the skin, in realistic conditions.



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