Extraction of betulin from the birch bark balance at pulp and paper production.

Abstract

The technical bark was used to obtain betulin; the one which is a barking of birch balance at pulp and paper production. The bark was prepared by grinding it on a crusher of abrasive action and fractionating, thus, the main fractions were obtained: less than 1 mm (35.4%), from 3 to 4.5 mm (31.5%). The bark was separated during the grinding process, the bark prevails in the coarse fraction, while bast is found in the fine fraction. For comparison, model samples of various sizes of birch bark were obtained by hand cutting. Chemical processing of bark fractions and model birch bark samples were carried out by the use of super-high frequencies (SHF) extraction with ethyl alcohol. Raw betulin was settled from extracts. The yield of extractive substances and raw betulin was 12.1-21.9% and 5.1-16.7% from absolutely dry raw materials; the maximum yield was from a coarse fraction of the bark or from model samples with smaller particle sizes. The authors studied the kinetics of the yield of extractive substances depending on the duration of SHF-extraction for bark fractions and birch bark samples. The optimal duration of the extraction for bark fractions is 10 min, and for birch bark is 15 min. The quantitative content was determined by the high performance liquid chromatography (HPLC) method for the obtained samples of betulin raw material. The total content of triterpenoids in the samples is about 80%, the betulin share is between 70.3 72.1%, from the absolutely dry substances of the extract. Coarse fraction of the bark contains more of the main component as compared to other fractions. It is advisable to use the fine fraction of the bark as a source of phenolic substances.