Evaluation of selective extraction methods for recovery of polyphenols from pine

The extraction conditions have been evaluated concerning the recovery of specific polyphenols from Scots pine (Pinus sylvestris) knots by means of an accelerated solvent extractor. The composition of the extracts was determined by gas chromatography, gas chromatography-mass spectrometry, and high-performance size-exclusion chromatography. The main phenolic compounds are the stilbenes pinosylvin and its monomethyl ether and the lignan nortrachelogenin (NTG), and their amounts vary a lot from sample to sample. The sequential extraction with a nonpolar solvent as a first step for removing the lipophilic compounds was the most efficient approach for the recovery of both pinosylvins and NTG. For food applications, hot water and 85% aqueous ethanol were good solvents for the production of the substances in focus. An industrial knotwood sample from a pulp mill was sequentially extracted with cyclohexane and ethanol/water (95:5) in a large-scale Soxhlet equipment. The results show that the industrial production of pinosylvins and NTG from knots is feasible.