Investigation on the potential of poplar bark from short-rotation coppices as bio-based fungicidal additives

Abstract

Bark on trees protects the plant against environmentally adverse conditions as well as fungi and insect attacks. There are different chemical substances, mostly in the outer bark of trees, which can stop fungi from developing. Bark as a by-product of wood plantations is available in high quantity and can serve as an excellent source for the production of eco-fungicides. In the presented article, bark of various poplar clones from two short-rotation coppices (SRC) in Poland and Germany was examined to determine the chemical composition, the possible extraction of potential fungicides (terpenes, aromatic and phenolic substances), and influence of their extracts on slowing the growth of mold fungi. It was proved that the content of the fungicidal substances depends strongly on the clone type. Two methods of extraction—Soxhlet and batch—were compared to obtain fungicidal extracts. Fungicidal substances were found in extracts gained with both approaches. Triterpenes, fatty acids, aldehydes, and alcohols were primarily the active fungicides in the Soxhlet extracts, whereas phenolic substances act as fungicides in the batch extracts.

Extraction of Phenolic Compounds from Populus Salicaceae Bark

“…Furan derivatives detected in methanol fractions have also been detected in the hydrolysates of shrub species [71] and as bulk compounds of Populus tremuloides bark [25]. 5-hydroxymethylfurfural may also come from the hydrolysis of 5-hydroxymethylfurfural glycosides [26] or from the degradation of hexoses during the drying step. Both furanic compounds, together with furanol, were detected in significant amounts in these fractions, where the presence of saccharides was significant.…”

“…Phenol (peak #3) could only be found as a trace in EA1 and M4 (0.5%A), whereas catechol (peak #4) could be found in EA1-EA4 (3.2%A, 1.7%A, 2.7%A, and 0.9%A) and in M4 and M5 (2.6%A and 7.3%A). Catechol has also been found in poplar sawdust hydrolysis and in lignin depolymerization processes [58,59], as well as in poplar bark extracts, together with salicylic alcohol [26]. Indeed, catechol and salicylic alcohol are considered the main components in poplar bark extracts [25].…”

“…Although other aldehydes such as benzaldehyde and salicylaldehyde have already been detected in hexane extracts from poplar root, 4-methylbenzaldehyde could be synthesized from preformed salicinoids, a class of Salicaceae-specific phenolic glycosides derived from salicyl alcohol [23,66]. However, from a biochemical point of view, it is much more reasonable that compound #13 corresponds to 2,3-dihydrobenzofuran, given that benzofuranic compounds are derived from flavonoids [26,67].…”

“…Recently, Bremer et al have studied the potential of poplar bark extracts as biobased fungicidal additives [26]. Triterpenes, fatty acids, aldehydes, and alcohols were primarily the active fungicides in the Soxhlet extracts, the content of which was much dependent on the type of poplar species and on the age of the samples used.…”