In this paper we have reviewed recent research on the development of bio-based preservative formulations for wood done at the Department of wood science and technology, Ljubljana. Preservative formulations used in this investigation were prepared using plant polyphenols as biocidal agents. These nonstructural components of wood were stilbenes and flavonoids, and were extracted from wood of broken and less-utilized trees, respectively. Woody biomass of the lowest quality was selected as a row material for extraction. Pine knotwood (Pinus sylvestris and Pinus nigra) and black locust heartwood (Robinia pseudoacacia) were extracted with acetone. Obtained extracts were examined with gravimetrically, spectrophotometrically and with chromatographic analysis. Further on, purified stilbenes and flavonoids were prepared for the antifungal assay. The extracts were colorimetrically analyzed on antioxidant properties by measuring free radical scavenging activity. The resistance of with extractives impregnated wood was measured with a so-called mini-block test (modified EN 113). Wood of less durable conifers and deciduous tree species was impregnated in a vacuum-pressure chamber, whereat water solutions of the hydrophilic extracts were used. After impregnation, the retention of extracts in the wood matrix was examined gravimetrically and with microscopy (CLSM and SEM). Antifungal properties of wood extractives of pine and black locust were determined by in vitro measuring the inhibition of fungal growth, and with measuring the resistance of the impregnated wood against fungal decay. The results of the fungal tests clearly show that hydrophilic extractives of less-quality wood of pines and black locust inhibit both fungal growth and reduced fungal decay of wood. It was found that the wood extracts of pines and black locust can be referred as to natural antioxidants since they inhibited the activity of free DPPH radicals. The results of our investigation show that low-quality wood of broken and less-utilized trees can be explained as a relevant source of natural compounds with antifungal and antioxidant properties. Wood polyphenols could be used as natural biocidal agents in bio-based preservative solutions.

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