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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]

In this study the proportion of lignin in wood tissue was analysed in 36 Scots pines differing in their form of dead bark. Material for analyses came from pure pine stands aged 89-91 years located in northern Poland. Chemical analyses were performed in the mature wood zone comprising the last 10 diameter increments located at a height of 1.3 m (DBH). Results indicate differences in lignin content and growth rate in pines whose stems were characterized by different forms of dead bark. The study showed significant differences in lignin contents between trees with shell and scaly dead bark and trees with ropy bark form. Pines with ropy bark were characterized by the lowest lignin content in relation to trees having the other 2 forms of dead bark. Moreover, a relationship was observed between diameter growth rate and lignin content in wood tissue. [ABSTRACT FROM AUTHOR]