Optimized Birch Bark Extract-Loaded Colloidal Dispersion Using Hydrogenated Phospholipids as Stabilizer.

Rolf Daniels,Francis Kamau Mwiiri

doi:10.3390/pharmaceutics12090832

Abstract

This study investigated the formulation and processing of aqueous colloidal dispersions containing a birch bark dry extract (TE) as the active substance and hydrogenated phospholipids (Phospholipon 90H) as stabilizer, which can be used in the preparation of electrospun wound dressings. Colloidal dispersions manufactured using a two-stage homogenization process had a bimodal particle size distribution, which was most significantly (p < 0.0001) affected by the phospholipid content. The size of the single particles decreased from an average particle size of about 4 µm to a particle size of approximately 400 nm. Dynamic interfacial tension studies performed using a profile analysis tensiometer (PAT) showed that the phospholipids strongly declined the interfacial tension, whereas a further decrease was observed when phospholipids were combined with birch bark extract. Interfacial viscoelasticity properties analyzed using the oscillating drop technique resulted in an increase of both interfacial elasticity and viscosity values. These results indicated that the phospholipids are preferentially located at the lipophilic/water interface and a stable film is formed. Furthermore, the results point to a synergistic interaction between phospholipids and TE. Confocal Raman microscopy (CRM) suggested that the TE is predominantly located in the oil phase and the phospholipids at the interface.

Highlights

This study investigated the formulation and processing of aqueous colloidal dispersions containing a birch bark dry extract (TE) as the active substance and hydrogenated phospholipids (Phospholipon 90H) as stabilizer, which can be used in the preparation of electrospun wound dressings
Dynamic interfacial tension studies performed using a profile analysis tensiometer (PAT) showed that the phospholipids strongly declined the interfacial tension, whereas a further decrease was observed when phospholipids were combined with birch bark extract
These results indicated that the phospholipids are preferentially located at the lipophilic/water interface and a stable film is formed

Summary

Introduction

Dry extracts from the outer bark of birch consist mainly of pentacyclic triterpenes, which are known for various pharmacological properties such as anti-inflammatory, anti-viral, anti-cancer activity, and wound-healing effects [1,2,3,4,5,6,7,8]. A well-characterized commercially used triterpene dry extract from the outer bark of birch contains about 80% (w/w) betulin and is obtained by accelerated solvent extraction with n-heptane [9]. Only a few formulation concepts are known These include cosmetic water-in-oil creams, water-in-oil foams [8], and an oleogel consisting of TE and sunflower oil, which received the European marketing authorization in January 2016 [12]. To the best of our knowledge, an aqueous colloidal dispersion of TE has not been described so far

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Conclusion