Quality control of retinoids in commercial cosmetic products.

BACKGROUND: Retinoids are widely used in different cosmetic products because of general improvement of skin appearance. However, retinoid concentration in cosmetics is restricted, and one particular form-retinoic acid, is banned in cosmetics due to safety reasons. AIMS: Within this study, we aimed to examine the quality of a considerable number of commercial retinoid cosmetic products in terms of their content and labeling, including also screening for the presence of retinoic acid. METHODS: An appropriate analytical methodology, based on HPLC-UV for the simultaneous determination of common retinoids, along with a screening method for retinoic acid, was developed and validated. Structural identity confirmation of the newer retinoid-hydroxypinacolone retinoate, was performed by LC-MS. RESULTS: Retinol and retinyl palmitate were most often found, in concentrations mostly below 0.3%, and up to 1.3% retinol equivalents. Determined contents deviated significantly from the quantitatively declared ones in seven products (0%-130%). In more than half of the tested products, inconsistencies between the contained and labeled retinoid were noticed. These products, as well as 14 additional anti-age cosmetics, were screened for retinoic acid, which was detected in two products. CONCLUSIONS: The obtained results from retinoids assay in commercial cosmetic products confirmed that the proposed method is appropriate for their routine analysis. The presence of retinoic acid in two products and determined retinoid contents above the Scientific Committee on Consumer Safety recommendations in 20% of the tested cosmetics reveal the need for their more strict regulation and quality control to ensure their efficacy and safety.

Retinoid stability and degradation kinetics in commercial cosmetic products.

BACKGROUND: Retinoids as dermatological agents are effective against acne, psoriasis, skin aging, and other skin conditions. However, their susceptibility to degradation is a limiting factor for their widespread use. OBJECTIVES: Within this study, we aimed to provide comprehensive and evidence-based information on retinoid stability and degradation kinetics in commercial cosmetics, focusing on different factors affecting their stability. METHODS: A validated HPLC-UV methodology was utilized for determination of the most common retinoids in cosmetics (retinol, retinyl palmitate, ß-carotene) and a newer promising retinoid (hydroxypinacolone retinoate). The stability of 16 retinoid derivatives in 12 commercial cosmetics was evaluated within 6 months of long-term and accelerated stability testing in addition to a one-week photostability study. Retinoid degradation in the tested formulations followed first-order kinetics, which was further applied to shelf-life prediction. RESULTS: Long-term and accelerated stability testing revealed retinoid instabilities in almost all products, resulting in a 0%-80% decline after 6 months at 25°C and a 40%-100% decline at 40°C, which were kinetically evaluated. Light degradation was more pronounced than temperature-induced degradation. Among the studied retinoids, the stability of the newer hydroxypinacolone retinoate was the most prominent. This study also identifies correlations between retinoid concentrations, price, formulation, and their stability in cosmetics. CONCLUSIONS: Retinoid instabilities were formulation-dependent and associated with lower contents than declared in some cosmetics. Retinoid chemical stability and physical stability in topical formulations need to be evaluated by real-time stability studies, instead of the more frequently used accelerated stability studies.