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Residues of wood, such as bark, represent an attractive source for natural antioxidants. The aim of this study was to evaluate the total polyphenols, heavy metals content and antioxidant capacity from oak (Quercus robur L.) and pine (Pinus sylvestris L.) barks grown in the central region of Poland. Identification and quantification of flavonoids and phenolic acids were done by HPLC-MS analysis. The phenolic extraction yields for oak barks were higher than for pine barks, while higher content of total flavonoids was determined in pine bark extracts. Generally, the content of the metals in raw barks and their extracts decreased in the order: Zn > Cu > Cr > Pb > Ni > Cd. The extracts were able to quench DPPH· radicals and to reduce the cupric complex exhibiting good antioxidant properties. They can be utilised as additives in nutraceutical and cosmetic products as well as for wood preservative materials. [ABSTRACT FROM AUTHOR]

The woodworking industry generates a great amount of bark which has not yet found a wider industrial application. None of the previously conducted research has considered oak bark application (which is one of the most often processed wood species in Poland) as a filler for wood adhesives. Moreover, no studies have determined the properties of bark containing melamine-urea-formaldehyde resin (MUF), which increasingly replaces pure urea-formaldehyde adhesives. Thus, the aim of the study was to determine the possibility of grinded oak bark application as a filler for MUF adhesive in plywood manufacturing. The chemical composition of oak bark was evaluated. Properties of liquid resins, such as viscosity, gel time, pH, and solid content, were determined. Chemical interaction between the filler and resin was assessed with using Fourier-transform infrared (FTIR) spectroscopy. Plywood panels manufactured using MUF adhesive filled with different bark concentrations (10%, 15%, 20%, 25%) were tested in terms of such properties as formaldehyde release and bonding quality. Studies have shown an improvement in liquid resin properties. The course of FTIR spectra did not explain the chemical interaction between the polymer and the filler. The addition of oak bark at a concentration of 15% made it possible to produce plywood panels characterized by reduced formaldehyde release and improved bonding quality. [ABSTRACT FROM AUTHOR]