Paže, A.*, Zandersons, J., Rižikovs, J., Dobele, G., Jurkjāne, V., Spince, B. and Tardenaka, A. 2014. Apparatus and Selective Solvents for Extraction of Triterpenes from Silver Birch (Betula pendula Roth.) Outer Bark. Baltic Forestry 20(1): 88-97.

A method and apparatus for obtaining triterpene extracts and betulin from pelletized birch bark (fraction 0.4-2.0 mm), extracting with petroleum ether (PE140) (boiling temperature range 100-140ºC) at a boiling temperature was developed. In the extraction unit, the process was carried out in a flowing through type reactor in the flow of distilled solvent in the intensive mass exchange regime. The change in the solubility of betulin and other triterpenes of outer birch bark (OBB) in PE140 at varying temperature was used to realise the process. During the process, betulin in the purified crystal form precipitates in the intermediate crystalliser making up 40‒50% of the total amount of extractives, with the total betulin, lupeol concentration of 90‒93 wt.% o.d. crystals. Decreasing the temperature of the solution remaining in the unit’s evaporator, betulin – lupeol crystals with slightly decreased content of betulin, but increased content of lupeol settle. The intensive mass exchange extraction unit can be used also for OBB extraction with polar solvents (alcohols, acetone). The extraction time of pelletized (0.4‒2.0 mm) OBB in polar solvents did not exceed 3‒5 h. However, the action of the intermediate crystalliser was less efficient, therefore required cooling jacket temperature should be lower than 10ºC. The mother liquor, remaining after isolation of triterpenes from the extract, was collected in the evaporator. It contained about 38‒40% of lupeol (wt.% o.d. mother liquor extractives) and can be used for obtaining of pure lupeol.

Key words: outer birch bark, triterpenes, betulin, lupeol, petroleum ether, extraction.