J. Cosmet. Sci., 61, 269–278 (July/August 2010) 269 Structural characterization and stability of dimethylaminoethanol and dimethylaminoethanol bitartrate for possible use in cosmetic fi rming B. CLARES, M. A. RUÍZ, M. E. MORALES, J. A. TAMAYO, and V. GALLARDO LARA, Departamento de Farmacia y Tecnología Farmacéutica (B.C., M.A.R., M.E.M., V.G.L.) and Departamento de Química Farmacéutica (J.A.T.), Facultad de Farmacia, Universidad de Granada, 18071 Granada, Spain. Accepted for publication May 13, 2010. Synopsis 2-Dimethylaminoethanol (DMAE) (also known as deanol) has been used as an ingredient in skin care, and in cognitive function- and mood-enhancing products. It is marketed as a free base or salt, and in theory, the two forms should be equally effective and able to substitute for each other in pharmaceutical formulations. De- tecting possible alterations in the active principle is a basic part of preformulation studies. Accordingly, this study compared DMAE and DMAE bitartrate to identify potential alterations or differences between the free base and the salt that might compromise the long-term stability of cosmetic preparations at different tem- peratures, and also compared the behavior of the base substance and derivative alone and in solution. Samples were analyzed with different physicochemical methods such as differential scanning calorimetry, ultraviolet and infrared spectroscopy, and nuclear magnetic resonance spectroscopy. INTRODUCTION The search for new compounds to prevent or attenuate skin aging is a priority in current re- search on new active principles in cosmetics (1). Research in dermatology, neurology, and immunology has shown that the skin and brain are intimately related (2–4), and has given rise to a new discipline that combines neurology and cosmetic dermatology : “Neurocosmetic.” In light of social issues surrounding the overlap between cosmetic and pharmacological applica- tions of cosmetics, we have investigated treatments for drooping or fl accid skin. Some morphological changes that appear as a consequence of skin aging result in almost complete detachment of the epidermis and empty spaces within the dermis. As a result, parts of the skin can hang loosely like empty bags, leading to fl accid skin (5). Developments at the interface between neurology and cosmetic dermatology have led to the use of di- methylaminoethanol (DMAE) as an ingredient in skin tensors (6). Address all correspondence to M. A. Ruíz.
JOURNAL OF COSMETIC SCIENCE 270 2-Dimethylaminoethanol is an acetylcholine precursor (7) that has been found effective in oral formulations to treat hyperactivity in children (8). In 2002 it began to be used in topical for- mulations of cosmetic skin tensors (9,10). The commercial availability of different derivatives of DMAE should in theory make it possible to substitute different products for each other in formulations without technological problems arising from structural changes that might af- fect the effi cacy of the active principle. We therefore compared DMAE and DMAE bitartrate (Figure 1) to detect potential differences that might interfere with the long-term stability of different formulations under different conditions and storage temperatures. We also evaluated the behavior of DMAE and DMAE bitartrate alone and in solution. Samples were analyzed with different physicochemical methods that included ultraviolet (UV) and infrared (IR) spectroscopy, differential scanning calorimetry (DSC) for DMAE bitartrate, and nuclear magnetic resonance spectroscopy (1H-NMR). Because of its fl uid nature, free-base DMAE was not analyzed by DSC. MATERIALS AND METHODS MATERIALS The products used as ingredients in our formulations were: dimethylaminoethanol, a color- less liquid with a faint fi sh-like odor, supplied by Roig Farma-Grupo (Fagron, Barcelona, Figure 1. Molecular structure of DMAE. Figure 2. DSC thermogram of DMAE bitartrate at 25°C.
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