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Notes: This study investigated the effect of different treatments on skin permeability, in vivo in man, by two noninvasive methods: transepidermal water loss (TEWL) determination measured with an evaporimeter, and Laser Doppler velocimetry (LDV) to measure the lag time before the vasodilatation induced by application of methyl and hexyl nicotinates.Different treatments were performed on forearms of volunteers: 1. removal of the stratum corneum by stripping, 2. occlusion and hydration of the stratum corneum, 3. application of three surfactants in aqueous solution (Tween 60, sodium dodecyl sulphate and cetyl trimethylammonium bromide).Increase in TEWL and decrease in lag time before the vasodilating effects of nicotinates measured with LDV after all treatments confirmed the modifications in skin permeability. The variations observed were more or less significant depending on the treatment, the investigative method, and the molecule used for the penetration study. With methyl (hydrophilic) nicotinate, the more TEWL increased, the more lag time decreased. A significant decrease in lag time after hexyl (lipophilic) nicotinate application was observed when there was a very high increase in TEWL. The lipophilic nature of the stratum corneum barrier was confirmed in vivo. Use of these two complementary methods, TEWL and LDV, allows the evaluation in vivo of the effect of different treatments on skin permeability in man.

Notes: Triterpenic derivatives stimulate the total collagen synthesis of skin fibroblasts. Their incorporation within an o/ w/o multiple emulsion should protect them against oxidation, particularly for unsaturated derivatives and should lead to a modulated release after topical application. The influence of the incorporation of madecassic acid, asiaticoside and asiatic acid on the viscosity and the stability of a multiple o/w/o emulsion was studied. Rheological analyses were carried out by flow experiments in order to obtain the apparent viscosity and by the oscillatory technique to calculate the basic visceolastic parameters. The comparative stability study was assessed by the tracer release method with phthalic acid diethyl ester previously incorporated in the internal phase of the emulsions. Six months storage at room temperature and at 40°C did not affect the stability of emulsions with triterpenic substances. The in vitro percutaneous absorption of triterpenic derivatives was investigated by Franz diffusion cells in hairless rats. Triterpenic derivatives were analysed in stratum corneum, epidermis and dermis, by liquid chromatography. Correlations were established between the triterpenic derivatives structure (glycosylated or not) and their percutaneous absorption. O/w/o multiple emulsion seems to be an efficient vehicle to preserve these active substances and to control their distribution in the skin.〈section xml:id="abs1-2"〉〈title type="main"〉RésuméLes dérivés triterpéniques stimulent la synthèse du collagène total par les fibroplastes de la peau [1]. Leur incorporation au sein d'une émulsion multiple H/E/H devrait les protéger contre l'oxydation, en particulier pour les dérivés insaturatés. Ceci devrait conduire à une libération modulée après application topique.La première partie de ces travaux présente l'influence de l'incorporation d'acide madécassique, d'asiaticoside et d'acide asiatique sur la viscosité et la stabilité d'une émulsion multiple H/E/H. On a effectué des analyses rhéologiques par essais d'écoulement afin de connaître la viscosité apparente et par la technique d'oscillation pour calculer les paramètres viscoélastiques généraux [2]. L'étude de stabilité comparative a été effectuée selon la méthode de libération de marquer [3] avec de l'ester diéthylique d'acide phtalique préablement incorporé dans la phase interne des émulsions. Six mois de stockage à température ambiante et à 40°C n'ont pas altéré la stabilité des émulsions avec les substances triterpéniques.L'absorption percutanée in vitro de dérivés triterpéniques a étéétudiée avec des cellules de diffusion de Franz chez des rats chauves. Les dérivés triterpéniques ont été analysés dans la couche cornée, l'épiderme et le derme, par chromatograohie liquide. On a établi des corrélations entre la structure des dérivés triterpéniques (glycosylée ou non) et leur absorption percutanée.L'émulsion H/E/H multiple semble être un vecteur efficace pour préserver ces substances actives et pour maîtriser leur distribution dans la peau. © Rapid Science Ltd. 1998

Notes: This study shows the influence of a water-in-oil emulsion and an oil-in-water emulsion on the photochemical behaviour of four sunscreen preparations containing various amounts of three UV filters: octyl methoxycinnamate, butyl methoxydibenzoylmethane, and 4-methylbenzylidene camphor. With the stripping method in vivo, skin-product interactions were evaluated after topical application and ultra-violet exposure. Evaluations were also made under the same operating conditions as in determining sun protection factor in vivo. Results showed that each sunscreen preparation has a particular photochemical behaviour related to filter mixture and emulsion type. When developing a sunscreen preparation the choice of the emulsion type and filters is relevant for achieving optimum efficacy and spectral stability. Resume. L'objectif de cette etude a ete de montrer l'influence du type d'emulsion (eau dans huile ou huile dans eau a base de cristaux liquides) sur le comportement photochimique de quatre preparations solaires contenant differents taux de trois filtres: octyl methoxycinnamate, butyl methoxydibenzoylmethane et 4-methylbenzyli-dene camphor. Le methode du stripping, in vivo, permet d'evaluer les interactions peau-produit apres application topique et irradiation. De plus, l'evaluation est faite dans des conditions operatoires identiques a celles preconisees pour la determination des indices de protection solaire. Les resultats qui ont ete obtenus montrent que chaque preparation solaire a son propre comportement photochimique directement lie au type d'emulsion et au melange des filtres. Au cours du developpement d'un produit solaire les choix du type d'emulsion et du melange des filtres ont une influence significative sur son efficacite et sa stabilite spectrale.

Notes: The photoprotective efficacy of some topical sunscreens was determined ex-vivo by spectrophotometric assay using an irradiation monochromator and a diffuse reflectance sphere. Transmission scans were run from 400 to 290 nm through human epidermis samples before and after application of products and protection factors (PF) were calculated. The results are also expressed as the percentage of the radiation stopped by the products in each spectral range (UVB, short UVA and long UVA). All the formulations contained two chemical filters: butyl methoxy dibenzoyl methane and octyl methoxycinnamate in a range of concentrations. Estimates of the effectiveness of all products were higher than results in humans when calculated by this ex-vivo technique. Due to its high discriminant power, this method constitutes a useful tool in the formulation of sunscreens.