Sensory perception of textural properties of cosmetic Pickering emulsions.

OBJECTIVE: The increasing interest for the Pickering emulsions is based on the possibility to replace classical emulsifiers by the solid particles. This approach is extremely attractive for the cosmetic field. But, the main difficulty is to obtain stable emulsions with appreciable skin feel. However, there is no information about the texture of such systems. The aim of this study is to formulate and describe the textural properties of cosmetic Pickering emulsions compared with conventional systems. METHODS: Three metal oxides were selected: titanium dioxide, zinc oxide and silicon dioxide, able to form stable and totally emulsified systems. A conventional emulsifier was used to formulate the emulsion of reference. Finally, the mixture of two emulsifying systems, combining both, surfactant and particles, was also studied. Then, a sensory panel was asked to quantify the intensities of the perception of the seven discriminating attributes. RESULTS: Each particle brought its properties to the textural perception of the emulsion. TiO2 particles ensured the whitening effect of the emulsions, SiO2 provided the screech residue, whereas ZnO gave intermediate results. The conventional surfactant was perceived as glossy, greasy and more difficult to spread. The particle/surfactant mixtures gave mostly in-between results. CONCLUSIONS: The study shows that the sensory profile of Pickering emulsions is indirectly and directly governed by the particle properties used for the emulsion stabilization: indirectly, through affecting the emulsion orientation (oil in water or water in oil), the droplet organization and viscosity, and directly, through the particle perception on the skin surface.

OBJECTIF: L'intérêt croissant pour les émulsions de type Pickering repose sur la possibilité de remplacer les émulsifiants classiques par les particules solides. Cette approche est extrêmement attractive pour le domaine cosmétique. Mais, la principale difficulté est d'obtenir des émulsions stables avec un toucher agréable. Cependant, il n'y a aucune information sur la texture de tels systèmes. Le but de cette étude est de formuler et de décrire les propriétés de texture des émulsions cosmétiques de type Pickering par rapport aux systèmes conventionnels. MÉTHODES: Trois oxydes métalliques ont été sélectionnés: le dioxyde de titane, l'oxyde de zinc et le dioxyde de silicium, capables de former des systèmes stables et totalement émulsifiés. Un émulsifiant conventionnel a été utilisé pour formuler l'émulsion référence. Enfin, le mélange de deux systèmes émulsionnants, combinant à la fois le tensioactif et les particules, a également été étudié. Ensuite, un panel sensoriel a quantifié les intensités de perception des sept attributs discriminants. RÉSULTATS: Chaque particule a apporté ses propriétés à la perception de la texture de l'émulsion. Les particules de TiO2 ont assuré l'effet blanchissant des émulsions, SiO2 a rendu le résidu crissant, tandis que ZnO a donné des résultats intermédiaires. Le surfactant conventionnel était perçu comme brillant, gras et plus difficile à étaler. Les mélanges particules/tensioactifs ont donné principalement des résultats intermédiaires. CONCLUSION: L'étude montre que le profil sensoriel des émulsions Pickering est indirectement et directement gouverné par les propriétés des particules utilisées pour la stabilisation de l'émulsion: indirectement, en contrôlant l'orientation de l'émulsion (huile dans l'eau ou eau dans l'huile), l'organisation des gouttelettes et la viscosité, et directement, grâce à la perception des particules à la surface de la peau.

Determination of galactose and mannose residues in natural galactomannans using a fast and efficient high-performance liquid chromatography/UV detection.

The present work describes the validation of an easy, fast and efficient precolumn derivatization method for the quantification of oligosides, mannose and galactose obtained by degradation of galactomannans. This work combines an acid hydrolysis and an enzymatic degradation of natural galactomannans with the quantification of released residues by reversed-phase HPLC-UV, the most usual HPLC system in laboratories. In case of enzymatic degradation, mannotetraose has been detected and quantified for the first time, and an application to the evaluation of the galactosyl distribution in galactomannans is proposed. After an acidic hydrolysis, this method also allowed to obtain the mannose/galactose (M/G) ratio.

Pi-aromatic and sulfur nucleophilic partners in cationic pi-cyclizations: intramolecular amidoalkylation and thioamidoalkylation cyclization via omega-carbinol lactams(1, 2).

NaBH(4) reduction of imides 1 and 6a,b,c followed by a pi-cyclization of the resultant N-acyliminium ions, generated in trifluoroacetic acid conditions, afforded two positional isomers, isoindolobenzothiazolinones 4 and 8, respectively. These ring closures proceeded via an intramolecular alpha-amidoalkylation with the classical pi-aromatic or the atypical sulfur atom as an internal nucleophile. A ready access to the related six-membered N,S-heterocyclic compounds such as isoindolobenzothiazinones 20a and 21a is also described. During this reaction, we have shown that omega-carbinol lactam precursor 14a led to endocyclic and exocyclic N-acyliminium ions 18a and 19a in equilibrium via the cyclic aza-sulfonium ion A. The latter furnished the expected products 20a and 21a in good yields. Similarly, different omega-carbinol lactams 14b-e substituted at C-angular position afforded the corresponding isoindolobenzothiazinones 20b-e and 21b-e bearing an angular alkyl, aralkyl, or aryl group. In the case of methyl 14b and benzyl 14e groups, an additional amount of the dehydration products 16b and 31 was isolated. These results indicate that the isomerization-pi-cyclization takes place via the cleavage of the thioether linkage in acidic medium.

Formation of new 5,11b-bridged isoindolo

[formula: see text] The tandem Pummerer/pi-aromatic cyclization of alpha-acyliminium ion, leading efficiently in "one pot" to thiopoxyareno-bridged isoindoloisoquinolinone incorporating the arylthio group, has been demonstrated for the first time. During this sequence the angular hydroxylated isoindoloisoquinolinone, resulting from the Pummerer-type cyclization, was also obtained.