Development of a modified-release hydrophilic matrix system of a plant extract based on co-spray-dried powders

The aim of this paper was to develop a modified-release solid dosage form containing a plant extract, namely Hamamelis virginiana extract. To this purpose, a co-spray-dried powder consisting of H. virginiana extract, sodium carboxymethylcellulose (Na-CMC) and colloidal silicon dioxide (SiO2) was formulated, which showed good flow properties for direct compression and was useful as a modified-release hydrophilic matrix system. H. virginiana extract was selected as a model plant extract due to its extensive use in treatments for chronic varicose veins. Different ternary co-processed powders were obtained by modifying the viscosity grade and concentration of Na-CMC. For a given set of spray-drying operating conditions, the use of medium viscosity (MV) Na-CMC in the formula led to high process yields and satisfactory product moisture contents. Compacted powders were able to modulate the extract release in different media, being the polymer concentration the fundamental factor affecting the rate of drug release. The co-spray-dried powder with a plant extract solid residue:SiO2:Na-CMC MV ratio of 1:1:0.075 was the best formulation because of its good flowability, compactability, stability and release properties. It was found that the release mechanism was a combination of extract diffusion and matrix erosion. The results indicated that the co-spray-drying of adequately designed formulations is a good strategy to improve the functionality of medicinal plant extract powders.