[Synthesis of betulinic acid from betulin and study of its solubilization usingliposomes]

A method for betulinic acid synthesis from betulin was developed. Betulin was oxidized with chromium oxide (VI) into betulonic acid, which was reduced with sodium borohydride to yield a mixture of 3-hydroxy epimers containing 85% of the natural beta-epimer. Studying changes in light scattering by dispersions of liposomes with different contents of betulinic acid revealed that up to 10 mol % of this compound may be entrapped in liposomes. The dependence of the efficiency of the betulinic acid entrapment on liposome composition was studied. The presence of polyvinylpyrrolidone or Proxanol increased the resistance of betulinic acid-containing liposomes to aggregation. These polymers solubilized betulinic acid with the same efficiency as liposomes.