Abstract
Birch bark contains extractive substances of the lupan types that have pharmacological activity and are of interest for obtaining new medicines. The predominant component of external birch bark extracts is pentacyclic triterpene alcohol - betulin. Allobetulin (19,28-epoxy-oleanan-3-ol) is an isomer of betulin and belongs to the pentacyclic triterpenoids of the oleanane types. Allobetulin and its derivatives are non-toxic compounds and they have antiviral, antimicrobial and antitumor activities. A new one-step method for producing allobetulin directly from birch bark by combining the stages of betulin extraction with ethanol and its isomerization into allobetulin in the presence of phosphoric acid catalyst was developed. The effect of the duration of birch bark treatment with ethanol and H3PO4 content on the yield of allobetulin was esteblished. The highest yield of crude allobetulin (35% by weight of a.s.b.) is achieved at a process duration of 8 hours in the presence of 5% H3PO4 and also at a duration of 15 hours in the presence of 3% H3PO4. The yield of recrystallized allobetulin is about 22% of the weight of absolutely dry birch bark.
 The composition of the allobetulin sample after recrystallization from isopropanol was confirmed by elemental analysis and its structure by – IRS and 1H NMR methods.
 The antioxidant properties of allobetulin were established in vivo and in vitro experiments.
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