PHENOLIC COMPOUNDS OF PICEA OBOVATA LEDEB. BARK

Abstract

Chemical composition of a phenolic complex of the Siberian spruce bark (Picea obovata Ledeb.) and a structure their oligomeric phenolic compounds are studied.The samples of the spruce bark have been collected in the vicinity of Fr. Baikal in September 2015. Extractive substances were recovered from the crushed bark by extraction with ethyl acetate at the boiling point of the solvent for 4 hours. The resinous substances were extracted from the obtained ethyl acetate extracts by hexane by the infusion method for 3 days. The bark samples, after extraction with ethyl acetate, were dried to remove solvent residues, then the water-soluble substances were extracted by extraction with distilled water at 90 °C for 4 hours.The yields of the extractive substances extracted with ethyl acetate and water from the spruce bark were 3,4 and 6,9% in absolutely dry bark (a.d.b.), respectively. The content of phenolic compounds in the ethyl acetate extract of the spruce bark have been 42,4% relative. The ethyl acetate extract of a spruce bark, pretreated with hexane, was fractionated on a silica gel column using mixture chloroform-acetone as the eluent with an increase in the fraction of the latter (from 0 to 100%). The content of monomeric and oligo-, polymeric phenolic compounds in the extract was determined.Based on the data of 1Н and 13C NMR spectroscopy, it was established that the flavonoid dihydroquercetin and stilbene glycosides – isorhapontin and astringin are the main monomeric phenolic extractive substances of Siberian spruce bark. It is shown that the structure of oligomeric phenolic compounds of the spruce bark includes structural fragments of stilbene glycosides, mainly monomeric blocks with the structure of isorhapontin and astringin.