Abstract
Extracts from white birch have been reported to possess antimicrobial properties, but no study has linked the chemical composition of bark extract with antimicrobial activity. This study aimed to identify white birch (Betula papyrifera Marshall) bark extracts with antimicrobial activity and elucidate its composition. In order to obtain the highest extraction yield, bark residues >3 mm were retained for extraction. A total of 10 extraction solvents were used to determine the extraction yield of each of them. Methanol and ethanol solvents extracted a greater proportion of molecules. When tested on eight microorganism species, the water extract proved to have the best antimicrobial potential followed by the methanol extract. The water extract inhibited all microorganisms at low concentration with minimal inhibitory concentration between 0.83 and 1.67 mg/ml. Using ultraperformance liquid chromatography coupled to a time‐of‐flight quadrupole mass spectrometer, several molecules that have already been studied for their antimicrobial properties were identified in water and methanol extracts. Catechol was identified as one of the dominant components in white birch bark water extract, and its antimicrobial activity has already been demonstrated, suggesting that catechol could be one of the main components contributing to the antimicrobial activity of this extract. Thus, extractives from forestry wastes have potential for new applications to valorize these residues.
Highlights
More than 50 million tons of bark, mainly derived from pulp and wood industries, are produced annually in North America (Gupta, 2009)
Recent studies have revealed that forestry wastes such as bark possess potentially important properties for new applications, which are related to their chemical content (Feng, Cheng, Yuan, Leitch, & Xu, 2013; Jablonsky et al, 2017)
By comparing the last two thin‐layer chromatography (TLC) plates, it is interesting to note that the two lines of purple spots at the top of the second plate likely corresponded to phenolic compounds, since they are found at the same position (Rf of 0.8 and 0.9; Figure 2b) than the spots at TA B L E 1 Antimicrobial activity of white birch bark extracts against different strains of microorganisms
Summary
More than 50 million tons of bark, mainly derived from pulp and wood industries, are produced annually in North America (Gupta, 2009). The white birch (Betula papyrifera Marshall), one of the broad‐leaved species widely present in the boreal forest of North America, con‐ tains a large amount of bioactive molecules including terpenoids and phenolic compounds known to have antimicrobial and antioxidant properties (Mshvildadze, Legault, Lavoie, Gauthier, & Pichette, 2007; Royer et al, 2012). It comprises up to 20% of the dry weight of woody plants and contains various molecules (Tanase, Coșarcă, & Muntean, 2019) The extraction of such molecules for the valorization of bark residues prior to thermal energy production is an interesting way to make it economically and environmentally advantageous for several industries (e.g., pharma‐ ceutical, cosmetic, food, and sanitary industries). Plants are known to be rich in a wide variety of specialized (aka secondary) metabolites (e.g., phenolics, terpenoids, and alkaloids), often studied in vitro for their antimicrobial properties (Cowan, 1999; Royer, Prado, García‐Pérez, Diouf, & Stevanovic, 2013). Biologically active molecules obtained from the bark of white birch could be exploited on an industrial scale in order to valorize these abundant residues from forest wastes
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