Abstract
The extracts of Scots pine, Norway spruce, silver and white birches stem, bark, roots, leaves and needles contain several useful bioactive compounds that exhibit antibacterial activity against pathogens. Both phenolic extracts and essential oils are bacteriostatic against several bacteria. The main individual antibacterial phenolic compounds in Scots pine are pinosylvins that effectively inhibit growth of pathogens such as Bacillus cereus, Staphylococcus aureus and Listeria monocytogenes. From other phenolic compounds lignans appeared to be the least bacteriostatic and flavonoids tend to occur as glycosylated forms which have lower antibacterial activity than their aglycones. Gram-positive bacteria are generally more susceptible to plants bioactive compounds than gram-negative bacteria.
Highlights
Plants synthesise low molecular mass compounds, phytoalexins, which protect them against attacks by fungi, bacteria and insects [1,2]
Interest in natural bioactive compounds has arisen for their multiple biological effects, including antioxidant, antifungal and antibacterial activity
Essential oils and phenolic extracts have been tested against multi-drug-resistant human pathogens and intestinal bacteria, like methicillin-resistant Staphylococcus aureus (MRSA) [8,13,14,15,16,17,18,19]
Summary
Plants synthesise low molecular mass compounds, phytoalexins, which protect them against attacks by fungi, bacteria and insects [1,2]. The aim of this literature review is to clarify the antibacterial compounds present in the predominant tree species in Finland, Scots pine (Pinus sylvestris), Norway spruce (Picea abies), silver birch (Betula pendula) and white birch (Betula pubescens) The extraction of these valuable compounds from forest biomass is of special interest as they are available in different wood harvesting and industrial residues, such as bark, knots, stump and roots. The total phenolic concentration has been observed to vary a lot between the different parts of the tree: 76.0, 17.5 and 1.1 mg GAE g-1 for dried bark, needles and cork, respectively [35,36,37,38]. Stilbenes and flavonoids have been observed to show antibacterial activity against some pathogenic bacteria [30] (Table 2). The hydrophilic extracts from knotwood of several pines, rich in stilbenes, proved to be efficient antibacterial agents when tested against paper mill bacteria Burkholderia multivorans, Bacillus coagulans and Alcaligenes xylosoxydans [28]
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