Ultrasound and Microwave-Assisted Extraction of Elecampane (Inula helenium) Roots

The aim of the current research was to perform two "green chemistry" extractions (ultrasound and microwave irradiation) with methanol, 70% (v/v) ethanol and water for extraction of biologically active substances from elecampane (Inula heleniun L.) roots and to compare their contents in all extracts. The presence of carbohydrates (sugars, fructooligosaccharides and inulin), total phenols and flavonoids were established. In vitro antioxidant potential was also evaluated by four assays (DPPH, ABTS, FRAP and CUPRAC). Water extracts obtained by ultrasound-assisted extraction (UAE) showed the highest value of inulin (38 g/100 g dry weight plant material). The highest antioxidant activity was possessed by the 70% (v/v) ethanol extracts obtained by UAE: DPPH - 107.2 mM TE/g dw, ABTS - 86.0 mM TE/g dw, FRAP - 67.0 mM TE/g dw and CUPRAC -173.0 mM TE/g dw, respectively. The reason for this probably depended on the highest content of total phenols in the 70% UAE ethanol extract (7.9 mg GAE/g dw, phenolic acids (chlorogenic, caffeic, p-coumaric, sinapic and ferulic acids)}, especially chlorogenic acid (1.84 mg/g) and flavonoids (quercetin, kaempferol and catechin; 26.4 mg QE/g dw). UAE was evaluated as a promising approach for the simultaneous extraction of bioactive compounds (dietary fibers and antioxidants) from elecampane roots in comparison with microwave irradiation.