Interactions between molecules of oleic and oleanolic acid in the pharmaceutical formulations - physicochemical perspective
[ 1 ] Instytut Technologii i Inżynierii Chemicznej, Wydział Technologii Chemicznej, Politechnika Poznańska | [ D ] phd student | [ P ] employee
- mixed monolayers
- phase separation
- excess free energy of mixing
- interface stability
EN Oleanolic acid (OLA) and oleic acid (OA) are among the natural substances with significant therapeutic potential. Both substances are ubiquitous in the plant kingdom and are components of numerous pharmaceutical formulations. Due to the limited bioavailability of the OLA, nanotechnology-based drug delivery systems (like nanostructured lipid carriers or liposomes) are of particular interest nowadays. The amphiphilic properties of OLA (a representative of triterpenic acids) and OA (unsaturated fatty acid) enable the use of the Langmuir monolayer technique for the physicochemical analysis of the mixed OLA-OA biomimetic system. Our research aimed to determine the surface properties (morphology, miscibility, and rheological properties) of OLA-OA monolayers in various molar ratios to finally evaluate the influence of the film composition on the character of intermolecular interactions. We confirmed that the OLA-OA monolayers exhibit intermediate features compared to pure substances and the surface properties of the mixed systems strongly depend on their composition. We proved that the system with significant domination of OLA over OA is characterized by the best miscibility, due to the attractive intermolecular interactions presence. This, in turn, contributes to the increased monolayer stability. We have formulated a theory that in a system containing a small amount of OA, fatty acid molecules can penetrate between terpenoid molecules, affecting their orientation. On the other hand, the lack of miscibility between the film components in different molar proportions may result from the OA molecules exclusion from the monolayer and, consequently, phase separation [1,2]. This phenomenon causes film inhomogeneity and can make pharmaceutical formulations unstable. The results obtained may contribute to the development of drug delivery systems and the design of therapeutic systems with optimal properties.
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