Bioactive compounds from Norway spruce bark: Comparison among sustainable extraction techniques for potential food applications

Picea abies (L.) Karst, (Norway spruce) bark, generally considered as wood industry waste, could potentially be used as a valuable source of antioxidants for food applications. In this study, supercritical fluid extraction (SFE), pressurized liquid extraction (PLE), and ultrasound-assisted extraction (UAE) were carried out in order to recover bioactive compounds from bark of Norway spruce. Obtained results show that PLE with ethanol as solvent was the most effective method for extracting total flavonoid compounds (21.14 ± 1.42 mg quercetin g−1 sample) and consequently exerted the highest antioxidant activity measured by 2,20-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (257.11 ± 13.31 mg Trolox g−1 sample). On the other hand, UAE extract contained the maximum phenolic concentration (54.97 ± 2.00 mg gallic acid g−1 sample) and the most interesting antioxidant activity measured by the ferric-reducing antioxidant power (580.25 ± 25.18 µmol FeSO4 g−1 sample). Additionally, PLE and UAE have demonstrated great efficiency in the extraction of trans-resveratrol, quantified by HPLC (0.19 and 0.29 mg trans-RSV g−1 sample, respectively)