Isolation of bioactive compounds from spruce bark waste using sub- and supercritical fluids

Abstract

The aim of this study was to investigate the possibility of isolating bioactive phenolics compounds from spruce bark (Picea abies), using sub- and supercritical fluids. In order to improve the yields and to assure a higher recovery of the phenolic compounds, in the first part of this study, extraction of lipophilic compounds was performed using only supercritical (SC) CO2 as solvent. Amount of obtained lipophilic compounds was quantified. In the second step, to the SCCO2 a cosolvent was added, namely 70% (v/v) aqueous ethanol, in order to isolate the bioactive phenolic compounds more efficiently. Effect of temperature, pressure and cosolvent flow rate on the yield of phenolic compounds was observed, at 40–60°C, 100–200bar and at 1.2mL/min and 2.5mL/min, respectively. Obtained extracts were analysed for their total phenolics (TPC), tannins (TTC) and flavonoids (TFC) content, as well as their antioxidant activity using UV–vis spectrophotometric methods. The maximum extraction yield of phenolic compounds (30.46±1.20)% was achieved at 100bar pressure and 40°C and the determined total phenolics content was 314.49mg/g dry extract, the total flavonoids content was 100.67mg/g dry extract and the total tannins content was 26.38mg/g dry extract. Additionally, the content of different phenolic compounds, typically found in woody biomass was assessed using high pressure liquid chromatography, ferulic acid and p-coumaric acid being the two major quantifiable phenolic compounds identified. Lastly, the consumption of solvents for production of kg of product with highest possible purity was determined and discussed.