Abstract
The bark of various tree species is a byproduct of the forestry industry that is not used at its full potential, considering the wide range of phytochemicals that are contained in these vegetal matrices and the health benefits that these compounds could provide for society. Our goal was to assess and compare the phytochemical composition of some hydroalcoholic spruce (Picea abies) bark extracts attained by ultrasound assisted extraction (UAE) and microwave-assisted extraction (MAE) and their antioxidant and antibacterial effects. The levels of total phenolics and tannins in the bark extracts were determined using methods based on the Folin–Ciocâlteu reagent, while specific phenolic and volatile compounds were identified and quantified using an UPLC-PDA method and a GC-FID method, respectively. After the chemical composition assessment, the antioxidant capacity (AC) was evaluated by measuring the scavenging ability against two free radicals (DPPH and ABTS). The minimum inhibitory concentration (MIC) was determined to assess the antibacterial activity of the extracts. The results indicated that the extracts produced by UAE had higher contents of polyphenols and tannins and also a higher content of the main phenolic compounds identified, catechin and epicatechin, compared to the MAE extracts. In contrast the highest content of volatile terpenoids (mainly α- and β-pinene) was found in the MAE extracts. All of the tested extracts exhibited relatively high antioxidant activities (especially the UAE extracts) and low MICs against Gram-positive bacteria but were mildly efficient against Gram-negative bacteria. These findings show that the spruce bark might be an important source of bioactive compounds that can be easily extracted from these industrial secondary products. Various uses of this vegetal material may emerge, due to its antioxidant and antibacterial effects.
Highlights
For the entirety of human history, different tree barks were used for various purposes, including medicinal purposes such as the treatment or the prevention of many pathologies [1,2].Despite the health benefits provided by these raw materials, most of the bark’s parts that result after wood processing are still inefficiently used for thermal energy [3,4]
National Park site 2) extract produced by ultrasound assisted extraction (UAE), MT US—P. abies (Tas, ca) extract produced by UAE, MD US—P. abies (Dolhasca) extract produced by UAE, M1 M—P. abies (Maramures, ului Mountains National Park site 1) extract produced by microwave-assisted extraction (MAE), M2 M—P. abies
Another study showed that spruce bark extracts obtained by Soxhlet and supercritical carbon dioxide extractions may inhibit the growth of Enterococcus faecalis and Streptococcus thermophilus, because of the content in catechin, taxifolin, astringin, and isorhapontin [62]. These results suggest that our spruce bark extracts may exhibit this antibacterial activity because of the catechins present in the natural extracts, as other studies have shown the antibacterial properties of these compounds against bacterial strains such as S. aureus and E. coli [63,64]
Summary
For the entirety of human history, different tree barks were used for various purposes, including medicinal purposes such as the treatment or the prevention of many pathologies [1,2].Despite the health benefits provided by these raw materials, most of the bark’s parts that result after wood processing are still inefficiently used for thermal energy [3,4]. Polyphenols are secondary metabolites that are often found in the vegetal foodstuff [8], but lately, their presence was indicated in different tree barks [9,10] They have an essential role in the protection of the plant against external threats, such as bacterial and fungal pathogens, herbivores, and insects [11,12]. These secondary metabolites are essential for plant protection and environmental integration of the containing species, and possess various biological activities that may benefit human health, such as antioxidant [13,14,15], antibacterial [14,16], antiviral [17,18,19], antifungal [20,21,22], and antitumor [9,10,23] effects
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
