Alain Denis

Photochemical Behavior of a New Long-chain UV Absorber†, Derived from 4-tert-Butyl-4′-Methoxydibenzoylmethane¶

A new W filter, the 1‐(4‐tert‐butylphenyl)‐2‐decanyl‐3‐(4′‐methoxyphenyl)‐propane‐1,3‐dione, called C10‐DBM, was prepared by grafting a 10‐carbon aliphatic chain to the acarbonyl position of 4‐tert‐butyl‐4′‐methoxydibenzoylmethane (BM‐DBM), a well‐known and often used UV filter. The UV‐A absorption efficiency of organic solutions containing the new filter was tested and compared with identical solutions containing BM‐DBM with or without irradiation (xenon lamp). The originality of this new filter is that its UV‐A absorbance appeared during irradiation of the molecule. Although the molar absorption coefficient of C10‐DBM in the UV‐A domain was lower than that of BM‐DBM, the solutions absorption exhibited a much more photostable behavior under irradiation. In this study, we first demonstrated that C10‐DBM was a precursor of BM‐DBM (enol isomer) by means of high performance liquid chromatography followed by mass spectrometry. Indeed, we showed that the UV‐A absorption of C10‐DBM solutions appearing during the irradiation of the molecule was due to a Norrish‐II reaction (β‐cleavage), which induced the release of the BM‐DBM enol form and l‐decene. Then, we established a kinetic model for the photochemistry of C10‐DBM and fitted the variation of W absorption spectra to confirm the proposed mechanism.

Gingko biloba extract reduces VEGF and CXCL-8/IL-8 levels in keratinocytes with cumulative effect with epigallocatechin-3-gallate

In skin inflammation, vascular endothelial growth factor (VEGF) and CXCL-8/IL-8 play an important role and are produced by activated keratinocytes. Extracts from Ginkgo biloba leaves (GBE), widely used in phytotherapy, have been reported to exert antioxidant and anti-inflammatory properties in the skin. We therefore evaluated the effects of GBE on the release of VEGF and CXCL8/IL-8 by normal human keratinocytes (NHKs) activated by tumor necrosis factor α (TNFα). Moreover, as we previously showed that epigallocatechin-3-gallate (EGCG) reduces VEGF and CXCL8/IL-8 secretion in TNFα-activated NHKs, we also tested its effect in association with GBE. Our results showed that GBE exerted a potent inhibition on VEGF and CXCL8/IL-8 levels in activated cells. In association with EGCG, GBE down-regulated VEGF and CXCL8/IL-8 levels in a cumulative manner in TNFα-stimulated NHKs. These results suggest that GBE, alone or in association with EGCG may contribute to moderate inflammatory processes in skin diseases associated with angiogenesis.

Facteurs de la diagenèse précoce des biominéraux: Exemple d'un polypier de Porites de Nouvelle-Calédonie

Resume Un prelevement representant environ vingt annees de croissance dune colonie de Porites a ete etudiedun double point de vue: les valeurs du ∂O18 (mesurees par deux laboratoires independants) et levolution des compositions globales de la phase organique. Une bonne correlation est observee dans levolution de ces deux parametres. Le resultat de cette experience, de caractere ponctuel, est replace dans une presentation generale des caracteristiques des biomineraux. Il en resulte un certain renouvellement de notre representation des facteurs qui orientent leur diagenese dont les modalites devraient influencer les recherches paleoenvironnementales.

Skin Absorption Modulation: Innovative Non-Hazardous Technologies for Topical Formulations

The achievement of skin drug delivery needs to conciliate two paradoxical terms: firstly, the major barrier of permeation formed by the stratum corneum needs to be circumvented for skin drug delivery (i.e., skin absorption); secondly, the drug deposition within the skin should be ideally accomplished with a restricted percutaneous absorption. At strictly speaking, the terms of this paradox are not solvable, since Ficks laws stipulate that the rate of drug transport is not separable from the gradient of drug concentration. In this field, drug carriers as vehicle have been reported in the recent years as one of the most promising strategy to address skin drug delivery. Indeed, the passage of drug loaded particles through the stratum corneum and/or via the follicular ducts might (i) target the drug deposition in specific skin sites, (ii) control and sustain the cutaneous drug release, (iii) protect the drugs against substantial epidermal metabolism, and (iv) reduce the percutaneous absorption. The present paper reviews the different drug carrier systems which do not require solvent in their process, with their physicochemical characteristics, the mechanisms of drug delivery and drugs that were efficiently used as a penetrant.

Development and in vitro assay of oxidative stress modifying formulations for wound healing promotion

Often presented as metabolism byproducts, reactive oxygen species are linked to detrimental effects such as chronic wound, mutagenesis, cancer and skin ageing. However, recent in vitro and in vivo observations suggest that ROS, and mainly hydrogen peroxide, interfere with cell signaling acting like second messenger and inducing adaptive responses. This is particularly observed in skin wound healing where cells are exposed to H₂O₂ following injury. In this study, we developed and characterized an innovative formulation producing H₂O₂ at low concentrations, in order to mimic physiological inflammation phase. Then, this pro-oxidative formulation (CAM-GOx) was assayed in vitro on keratinocytes cell culture, compared to the blank formulation (CAM) and the anti-oxidative formulation (CAM-CAT) to assess whether oxidative stress was implied or not in cellular responses.

Skin Absorption Modulation: Innovative Non-Hazardous Technologies for Topical Formulations~!2009-07-31~!2009-12-10~!2010-04-23~!

The achievement of skin drug delivery needs to conciliate two paradoxical terms: firstly, the major barrier of permeation formed by the stratum corneum needs to be circumvented for skin drug delivery (i.e., skin absorption); secondly, the drug deposition within the skin should be ideally accomplished with a restricted percutaneous absorption. At strictly speaking, the terms of this paradox are not solvable, since Ficks laws stipulate that the rate of drug transport is not separable from the gradient of drug concentration. In this field, drug carriers as vehicle have been reported in the recent years as one of the most promising strategy to address skin drug delivery. Indeed, the passage of drug loaded particles through the stratum corneum and/or via the follicular ducts might (i) target the drug deposition in specific skin sites, (ii) control and sustain the cutaneous drug release, (iii) protect the drugs against substantial epidermal metabolism, and (iv) reduce the percutaneous absorption. The present paper reviews the different drug carrier systems which do not require solvent in their process, with their physicochemical characteristics, the mechanisms of drug delivery and drugs that were efficiently used as a penetrant.

A new concept of acne adjuvant cosmetic: correction of sebum quality and reduction of erythromycin resistance1

Background: Acne vulgaris is a multifactorial disease: an increased sebum production, an abnormal keratinisation and the proliferation of Propionibacterium acnes are major causes of this pathology. It explains that monotherapy is not as effective as combination of treatments. Dermocosmetical formulations are also prescribed to complete acne medical treatments in order to potentiate or correct secondary effects, via keratolytic and moisturizing activities.