Influence of grinding methods of birch bark on the yield of biologically active substances

Introduction. Birch bark contains biologically active substances (BAS). In this regard, the search for ways to increase yield of its bioactive agents is relevant.

Aim. To study the effect of birch bark grinding methods on the extract of its BAS during extraction.

Materials and methods. Samples of birch bark of silver birch (Betula pendula Roth.) and downy birch (Betula pubescens Ehrh.) were ground up on devices with various force effects on plant material — disk (mainly squeezing, shear, tensile and shearing forces), three-roll annular (crushing and abrasive forces) and ball (crushing, abrasive and shock-shear forces) mills. Morphological and microscopic studies were carried out, the content of extractive substances and moisture in the ground up samples was determined. The composition and content of BAS were analyzed.

Results. The smallest changes in the morphological and anatomical structure of plant material were observed when using a disk mill (the morphological features of birch bark and its cellular structure are preserved), grinding on three-roll ring and ball mills leads to serious changes in the morphological and anatomical structure of birch bark (the morphological and anatomical structure is lost, cell walls are destroyed). Comparative analysis of the yield of extractive substances from ground up birch bark samples, depending on the grinding method and the extractant used (purified water and ethyl alcohol of different concentrations: 96, 80, 70, 40, 20 and 10%) showed that the best extractant is 80% ethyl alcohol. The highest yield of extractive substances was noted for a sample of birch bark ground up in a ball mill — 36.85%, for ground up in a disc mill — 29.96%, on a three-roll ring mill — 30.88%. When studying the yield of the main groups of BAS (saponins, tannins, coumarins, hydroxycinnamic acids) from ground up birch bark samples, it was found that when using grinding methods that do not lead to the destruction of cell walls, the yield of BAS is limited by the capillary-porous structure of the plant material.

Conclusion. When using grinding methods that lead to the destruction of cell walls, the greatest yield of BAS from birch bark is observed in the case of using a more severe impact on it, including not only abrasion, crushing, but also impact (ball mills).

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