Spherical Amorphous Nanoparticles from Birch Bark Triterpenoids: Study of the Conditions for the Formation

Abstract

Triterpenoids from birch bark are valuable biologically active substances. They exhibit important biological properties. However, triterpenoids are insoluble in water due to their hydrophobicity. In order to increase their bioavailability we developed a technique for obtaining spherical amorphous nanoparticles (SANP) by their precipitation with water from a solution in THF. In the form of nanoparticles, triterpenoids show additional useful properties: they can be loaded with hydrophobic substances. SANP were also shown to be effective immunological adjuvants. This article is devoted to the study of conditions that could optimize their production. As a result, it was shown that among the three investigated solvents miscible with water - acetone, dioxane, THF -the latter gives the best results. Lowering temperature decreases the size of SANP. An increased temperature leads to the formation of betulin crystals. When the concentration of triterpenoids in THF is higher than 5 mg/ml, crystals of betulin also begin to form. The results of this study lead to the assumption that the main parameter of the process determining the formation of SANP is the rate of the solvent diffusion into water.

Keywords

• birch bark triterpenoids
• betulin
• lupeol
• spherical amorphous nanoparticles
• precipitation by water from an organic solvent