Organische Salze der Flufenaminsäure: Eine neue Stoffklasse zur Bildung lyotroper Mesophasen in wäßrigen Systemen

Eckert, Th.; Fischer, W.

doi:10.1007/bf01397893

Cited by 14 publications

(6 citation statements)

References 11 publications

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“…Similar calculations performed on flufenamic acid resulted in a conformation where the aromatic rings are not coplanar and the molecule has a length of ∼10 Å. This conformation is similar to that suggested for the molecule in the lamellar lyotropic phase . We therefore propose a bilayer structure of the organic template within the organic layers for both templates as illustrated in Figure .…”

Section: Discussionsupporting

confidence: 78%

Synthesis of Lamellar Mesostructures with Nonamphiphilic Mesogens as Templates

Zhao

Goldfarb

1996

Chem. Mater.

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Magnesium- and zinc-based lamellar mesostructures were synthesized with nonamphiphilic mesogens as templates. The templates used were disodium chromoglycate (DSCG) and flufenamic acid (FA) which are known to exhibit lyotropic liquid-crystalline phases in aqueous solutions. Evidence for the lamellar structure was obtained from the X-ray diffraction patterns and transmission electron micrographs. The interlayer spacings in the materials prepared with DSCG and FA, 30 and 24 Å, respectively, were large compared to the molecular dimensions of the templates, suggesting the existence of a bilayer arrangement of the templates between the inorganic walls. The presence of intact template molecules within the layers was confirmed by chemical analysis, TGA, IR, and NMR measurements. Interactions between the template molecules and the inorganic layer were evident through the increase in their decomposition temperatures as compared to the pure template and by the slight weakening of the CO bond as determined by the IR measurements. The synthesis of lamellar mesostructures with nonamphiphilic mesogens broadens the scope of the so-called “liquid-crystal template mechanism” in the sense that it is not limited to amphiphilic molecules but applies also to other molecules which can form large molecular assemblies in solutions.

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Section: Discussionsupporting

confidence: 78%

Synthesis of Lamellar Mesostructures with Nonamphiphilic Mesogens as Templates

Zhao

Goldfarb

1996

Chem. Mater.

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“…[40] Slow drug release can also intensify the characteristic of the active substance too, with oily or liquid phases as solvents, or at higher temperatures form mesophases. [41][42][43][44][45] Lyotropic or thermotropic liquid crystalline mesophases of the drug substance created in this way can interact with the liquid crystals of carrier base. Kriwet and Muller-Goymann's study shows that during this process drug molecules become part of the microstructure of created system, which decreases the speed of drug release from base.…”

Section: Water Distribution and In Vitro Dda Release Studymentioning

confidence: 99%

Natural Surfactant-Based Emulsion Vehicles: A Correlation Between Colloidal Structure and In Vitro Release of Diclofenac Diethylamine

Vucinic-Milankovic¹,

Savić

Vuleta

et al. 2010

Journal of Dispersion Science and Technology

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The need for an official pharmaceutical vehicle or carrier of drug based on natural sugar emulsifiers that protect and regenerate natural barriers of the skin lipid layer is constantly increasing. This article studies the specific structures of emulsions and two manners of water binding that provide prolonged skin moisturization and delayed or prolonged release of drugs insoluble in water. Natural emulsifiers of an alkylpolyglucoside (cetearyl alcohol and cetearyl glycoside) and estar-type (sorbitan stearate and sucrose cocoate) are used for manufacturing vehicle/carriers of drugs (diclofenac diethylamine). Specific hydrofilic groups in emulsifiers, such as glycozide and ester, are capable of binding in different manners and variable quantities of water by hydrogen bonds within the cream, which is responsible for water distribution and prolonged skin moisturization. This lyotropic potential of natural emulsifiers-alkylpolyglucoside and estar type-may affect the physical stability of topical vehicles by determining the colloidal structure, further reflecting the drug delivery from the pharmaceutical excipient to the skin. The aim of this article is to evaluate whether the type of emulsifier influences the structural characteristics of emulsion systems and how the content and availability of water within the cream reflects the delivery of diclofenac diethylamine (1.16%) from the topical vehicles. Freeze-fracture transmission electron microscopy, wide-angle x-ray diffraction, thermogravimetric analysis, and continual and oscilatory rheological measurements are employed for characterization of emulsion system colloidal structure. Diclofenac diethylamine release profiles from investigated emulsion systems were evaluated using the rotation paddle apparatus, modified by addition of diffusion cells (enhancer cell). There is an important difference in water distribution within the creams with emulsifiers of different chemical types. In the sample with ester-type sugar emulsifiers, the quantity of interlamellar-bound water is four times less than bulk and secondary water, while in the sample with alkylpolyglucoside emulsifier, approximately two thirds of total water are bound inside the system and one third is poorly bound, that is, bulk water. It can also be seen that diclofenac diethylamine is gradually released from the vehicle during 6 hours of testing. Formulation of topical vehicle as dermopharmaceutical drug carrier system, with natural emulsifier, like cetearyl alcohol, cetearyl glucoside, sorbitan stearate, and sucrose cocoate, is recommended.

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“…Die wesentlichen f3berstrukturen dieser Doppellamellen wurden mit Hilfe der Gefrierbruch-Elektronenmikroskopie dargestellt [1]. Die Notwendigkeit des Vorhandenseins der Trifluormethylgruppe fiir den fliissig-kristallinen Zustand des DEAF ftihrte zu dem Denkmodell einer Doppellamelle, in deren Innerem eine Wasserschicht eingelagert ist.…”

Section: Diethylammoniumflufenaminat (Deaf) Bildet In W~ilgrigenunclassified

“…Der flachere Abfall der Linienbreite nach der unteren Konzentrationsgrenze hin ist mit dem Auftreten einer ver~inderten fliissigkristallinen Struktur (Sph~iroide [1]) zu erkl~iren, deren isotrope Rotation zur Verminderung der dipolaren Wechselwirkungen und damit zur Zunahme der Relaxationszeiten fiihrt, ein Effekt, der ebenfalls bei Phospholipidvesikeln im Vergleich zum lamellaren Fliissigkristall auftritt [11]. In diesem Konzentrationsbreich treten planare Doppellamellen auf.…”

Section: Untersuchungen Zur Ionenpaarbildungunclassified

“…Zusammen mit der Tatsache, datg sich Mesophasen in dieser Stoffklasse nur bilden, wenn die CF3-Gruppe in sterisch richtiger Position zum Lamelleninneren steht, sind diese Ergebnisse als eine Best~itigung des Modells einer Doppellamelle anzusehen, das eine intralamellare Wasserschicht annimmt [1]. Durch die Resultate differentialcalorimetrischer Messungen ergibt sich eine Zunahme der Schmelzenthalpien der Mesophasen mit dem pro Mol DEAF gebundenen Wasser.…”

Section: Diskussionunclassified

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Organische Salze der Flufenamins�ure: Eine neue Stoffklasse zur Bildung lyotroper Mesophasen in w��rigen Systemen

Fischer

Eckert

1982

Colloid & Polymer Sci

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Zusarnrnenfassung: Diethylammoniumflufenaminat bildet in w~if~rigen L6sungen wasserstrukturerzwungene Ionenpaare. Die Bildungsenergie wurde zu -22,9 kJ/mol bestimmt. Die hohe Bildungenergie l~it~t das Diethylammoniumflufenaminat als praktisch undissoziierte Substanz erscheinen, die in dieser Form zu fliissig-kristallinen Strukturen assoziiert. Hierbei ist das an die Carboxylatgruppe gebundene Diethylammoniumion als der hydrophile Kopf des amphiphilen ,,Molekiils" anzusehen. 19F-NMR Messungen an den lamellaren Mesophasen des Diethylammoniumflufenaminat zeigen, daf~ fiir die Existenz der Fliissigkristalle eine Wechselwirkung der Trifluormethylgruppen mit Wasser erforderlich ist. Dies best~tigt die Vermutung, wonach im Inneren der Doppellamellen Wasserschichten eingelagert sind, die durch die Trifluormethylgruppen stabilisiert werden. Diese Wasserschichten bewirken ihrerseits dutch Dipol-Dipol-Wechselwirkungen mit den Trifluormethylgruppen den Zusammenhalt der Lamellen. Differentialcalorimetrische Untersuchungen des Schmelzverhaltens und der Wasserbindung der Lyomesophasen zeigen einen Zusammenhang zwischen dem an das Diethylammoniumflufenaminat gebundenen Wasser und den Schmelzenthalpien der Mesophasen. Daraus kann geschlossen werden, daft es sich beim Schmelzen der Mesophasen eigentlich um das ,,Schmelzen" des gebundenen Wassers handelt, d. h. Freisetzung der Wassermolek/fie aus den Hydrath/.illen der hydrophilen K6pfe und Trifluormethylgruppen der Diethylammoniumflufenaminat-Ionenpaare. Auch dieses Verhalten steht in L~bereinstimmung mit dem oben genannten Lamellenmodell.

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Organische Salze der Flufenaminsäure: Eine neue Stoffklasse zur Bildung lyotroper Mesophasen in wäßrigen Systemen

Cited by 14 publications

References 11 publications

Synthesis of Lamellar Mesostructures with Nonamphiphilic Mesogens as Templates

Synthesis of Lamellar Mesostructures with Nonamphiphilic Mesogens as Templates

Natural Surfactant-Based Emulsion Vehicles: A Correlation Between Colloidal Structure and In Vitro Release of Diclofenac Diethylamine

Organische Salze der Flufenamins�ure: Eine neue Stoffklasse zur Bildung lyotroper Mesophasen in w��rigen Systemen

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