Determination of antioxidant efficacy of cosmetic formulations by non-invasive measurements

Background/aims: Antioxidants have been proposed, over the last decade, as functional ingredients for anti aging preparations and to prevent and modulate oxidative skin damages. Up to date, beside the photo-induced oxidative skin damages model, none in vivo protocols have shown sufficient reproducibility for the validation of the antioxidant claim for a cosmetic finished product. To this aim, we have recently anticipated a new in vivo protocol based on a microinflammatory model, driven by reactive oxygen species. In the present study our model was validated by comparison with four different instrumental methods. Methods: The effects of a pre-treatment of two different formulations based on antioxidant functional ingredients, were investigated on forearm skin of 15 healthy volunteers, and compared to a cosmetic base and control area. The instruments considered in the study were Chromameter (CR-300 Minolta), Tewameter TM 210 (Courage-khazaka, Cologne, Germany), Laser Doppler Perfusion Imager (PIM1.0 Lisca Development AB, Sweden), in comparison to DermAnalyzer(R), an easy to use software program developed by us, using the CIE L*a*b* color space parameters. Results: The comparative measurements showed that the antioxidant formulations tested were all able to reduce, in different but statistically significant extent, the intensity of skin redness, and of cutaneous blood flow, when compared to control area (P<0.0001). Conclusions: The methyl nicotinate (MN) based microinflammatory model, in conjunction with objective measurements, resulted an effective tool for in vivo assessment of oxidative skin injuries. In view of the high level of repeatability, short time of answer and simplicity, the procedure by us developed, is proposed as a possible protocol for the evaluation of in vivo efficacy of antioxidant functional ingredients in cosmetic formulations.