Marine Canton

Les extraits naturels représentent une source importante d'ingrédients biologiquement actifs potentiellement intéressants pour l'industrie cosmétique. La présence de ces ingrédients dans les produits commercialisés a donné lieu à une réglementation rigoureuse afin de garantir leur activité, sécurité et stabilité. Une procédure analytique innovante permettant l'identification rapide des composés connus dans un extrait naturel a été développée à l'Université de Reims Champagne Ardenne en 2014. Cette procédure combine des outils de chromatographie (Chromatographie de Partage Centrifuge, CPC), de spectroscopie (Résonance Magnétique Nucléaire, RMN) et de classification des données. En pratique, de nombreux extraits naturels sont conçus ou stabilisés dans des solvants à haut point d'ébullition tels que le glycérol ou les glycols. Ces derniers interfèrent avec le fractionnement par CPC et compliquent l'analyse par RMN. La méthode de déréplication actuellement utilisée en routine sur les extraits secs doit donc être optimisée. La nouvelle stratégie, développée dans le cadre d'une collaboration entre les laboratoires Pierre Fabre Dermo-Cosmétique et l'Institut de Chimie Moléculaire de Reims, est présentée ici. Deux méthodes complémentaires ont été développées afin de supprimer l'influence des solvants à haut point d'ébullition sur la procédure et ainsi obtenir le profil chimique d’un extrait naturel dans les meilleures conditions de fiabilité : une suppression physique du solvant par CPC et une suppression spectroscopique de ses résonances par RMN du 13C. A travers des exemples concrets, nous démontrons que la combinaison de ces deux approches permet la caractérisation chimique globale des extraits naturels dilués dans des solvants à haut point d'ébullition.

Many natural extracts used as cosmetic ingredients are available as solutions prepared in high-boiling-point solvents, called carrier solvents, such as propylene glycol (1,2-propanediol), propanediol (1,3-propanediol) and glycerin. The upstream chemical profiling of these extracts represents a major asset for the cosmetic industry, because it accelerates product development. A new workflow for the rapid characterization of the main metabolites present in natural extracts diluted in propylene glycol and 1,3-propanediol is presented here as an extension of previous works on glycerin-containing extracts. This method is an optimized version of a well-established dereplication procedure and consists of a fractionation by centrifugal partition chromatography followed by ¹³C nuclear magnetic resonance analysis and dedicated data processing. The concentration by evaporation under reduced pressure was considered as a pertinent preliminary step, particularly adapted to the analysis of highly diluted extracts. A dried hydro-ethanolic extract of Leontopodium alpinum Cass. was prepared at laboratory scale and used for method validation. Three solutions at 5% wt. of dry extract were prepared with propylene glycol/water (1:1), 1,3-propanediol/water (1:1) and glycerin/water (1:1) as carrier solvents. The dereplication workflow was applied to the three resulting L. alpinum extracts. Each study led to the quick identification of 26 metabolites including five flavonoids (luteolin and its derivatives), five hydroxycinnamic acids (among which are leontopodic acids), sugars and organic acids.

For scientific, regulatory, and safety reasons, the chemical profile knowledge of natural extracts incorporated in commercial cosmetic formulations is of primary importance. Many extracts are produced or stabilized in glycerin, a practice which hampers their characterization. This article proposes a new methodology for the quick identification of metabolites present in natural extracts when diluted in glycerin. As an extension of a ¹³C nuclear magnetic resonance (NMR) based dereplication process, two complementary approaches are presented for the chemical profiling of natural extracts diluted in glycerin: A physical suppression by centrifugal partition chromatography (CPC) with the appropriate biphasic solvent system EtOAc/CH₃CN/water 3:3:4 (v/v/v) for the crude extract fractionation, and a spectroscopic suppression by presaturation of ¹³C-NMR signals of glycerin applied to glycerin containing fractions. This innovative workflow was applied to a model mixture containing 23 natural metabolites. Dereplication by ¹³C-NMR was applied either on the dry model mixture or after dilution at 5% in glycerin, for comparison, resulting in the detection of 20 out of 23 compounds in the two model mixtures. Subsequently, a natural extract of Cedrus atlantica diluted in glycerin was characterized and resulted in the identification of 12 metabolites. The first annotations by ¹³C-NMR were confirmed by two-dimensional NMR and completed by LC-MS analyses for the annotation of five additional minor compounds. These results demonstrate that the application of physical suppression by CPC and presaturation of ¹³C-NMR solvent signals highly facilitates the quick chemical profiling of natural extracts diluted in glycerin.

The analysis by proton-decoupled carbon-13 nuclear magnetic resonance spectroscopy of samples dissolved in solvents presenting strong multiple resonances can be facilitated by the suppression of these resonances by multisite presaturation. The advantage drawn from this operation is the elimination of the possible artifacts that arise from the solvent signals in non-optimized decoupling conditions. Solvent presaturation was implemented on glycerol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, and 1,3-butanediol with at least 94 % on-resonance efficiency and a bandwidth of less than 50 Hz measured at 50 % signal intensity decrease. The experimental measurement of the signal suppression bandwidth leads to unexpected selectivity profiles for close-frequency resonances. Computer resolution of the Bloch equations during multisite presaturation provide an insight into the origin of the observed profile perturbations.

The analysis by proton-decoupled carbon-13 nuclear magnetic resonance spectroscopy of samples dissolved in solvents presenting strong multiple resonances can be facilitated by the suppression of these resonances by multi–site presaturation. The advantage drawn from this operation is the elimination of the possible artifacts that arise from the solvent signals in non–optimized decoupling conditions. Solvent presaturation was implemented on glycerol, 1,2–propanediol, 1,3–propanediol, 1,2–butanediol, 1,3–butanediol with at least 94 % on–resonance efficiency and a bandwidth of less 5 than 50 Hz measured at 50 % signal intensity decrease. The experimental measurement of the signal suppression bandwidth leads to unexpected selectivity profiles for frequency close resonances. Computer resolution of the Bloch equations during multi–site presaturation provide an insight into the origin of the observed profile perturbations.