Screening of Functional Compounds in Supercritical Carbon Dioxide Extracts from Perennial Herbaceous Crops

The bio-based economy concept requires using biomass not only for energy production but also for bioactive compound extraction, application or biotransformation. This study analyzed the possibility of obtaining bioactive compounds from biomass before its transformation into biofuel. This involved an analysis of the total content of polyphenols (TPC), flavonoids (TFC), and spectral analysis using Fourier transform infrared spectroscopy (QATR- FTIR) as well as analysis of the antioxidant activity of extracts from selected perennial herbaceous crops cultivated on marginal lands in Poland. The extracts were obtained by supercritical carbon dioxide extraction (scCO2) or scCO2 with water as a cosolvent (scCO2/H2O) from biomass of the following plants: Helianthus salicifolius, Silphium perfoliatum, Helianthus tuberosus, Miscanthus × giganteus, Miscanthus sacchariflorus, Miscanthus sinensis and Spartina pectinata. The biomass was harvested twice during the growing period (June and October) and once after the end of the growing period (February). For most of the analyzed extracts obtained from biomass at the growing stage using scCO2 or scCO2/H2O, a higher TPC was noted than for samples of semi-wood or straw biomass obtained after the end of the growing period. Higher contents of polyphenolic compounds were recorded in extracts obtained using scCO2/H2O. A positive correlation between TPC and antioxidant activity was noted for the analyzed substrates. Flavonoid contents varied in the analyzed samples, and higher contents were generally obtained in scCO2 extracts from biomass harvested at the beginning of the growing period. A high diversity of extract compositions was confirmed by spectral analysis. The presented data can be used at the initial stage of planning a biorefinery.