Isolation of Dihydroquercetin and Arabinogalactan from Larch Wood by Water-Ethanol Solutions

Siberian larch wood ( Larix sibirica Lebed.) contains such valuable biologically active substances as dihydroquercetin (DHQ) and arabinogalactan (AG), promising for the use in the pharmaceutical and food industries. An urgent task is to improve the methods of extraction isolation of these compounds from wood. In this work, we studied the possibility of simultaneous isolation of dihydroquercetin and arabinogalactan by extraction of larch wood with 5–25% aqueous ethanol solutions. It has been shown that by extracting wood with aqueous solutions with a low concentration of ethanol, it is possible to exclude the stage of separation of resinous substances from the target products of DHQ and AG. By experimentally optimizing of water-ethanol extraction process, it was shown that the highest yields of DHQ (1.8% mas.) and AG (18.0% mas.) were achieved by extraction of larch wood, crushed to particles of 1–3 mm in size, with a 15% ethanol solution for 2 h. It is shown that the preliminary mechanical activation of larch wood allows to reduce the duration of water-alcohol extraction to 30 minutes and to obtain DHQ and AG with high yield. The structure of DHQ and AG is confirmed by IR and NMR spectroscopy. The identification and purity of the DHQ isolated from larch wood was confirmed by photometric method using the cyanidine chloride formation reaction when heating the DQV in ethanol in the presence of hydrochloric acid.