Abstract
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 2,2′-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).
Highlights
A considerable amount of bark waste is generated as by-product from the industrial wood transformation
Results obtained from ultrasound-assisted extraction (UAE) extraction highlighted that UAE yield was higher than SFE_40 yield and comparable to that of the PLE_EtOH extract
In order to highlight some possible relationships among the values reported in Table 2, a remarkable correlation between total phenolic content (TPC) and FRAP assay can be found with both the extraction methods adopted [22]
Summary
A considerable amount of bark waste is generated as by-product from the industrial wood transformation. Spruce bark is especially rich in glycosylated monomeric stilbenes (astringin, piceid, and isorhapontin) and their corresponding aglycone forms (piceatannol, resveratrol, and isorhapontigenin) [6]. Among these different kinds of stilbenes, trans-resveratrol (trans-3, 5, 40 -trihydroxystilbene; trans-RSV) has attracted great attention. It is a natural polyphenolic compound found in a variety of food and in bark tree [7]. It is widely used in cosmetics and dermatology [13]
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