Investigation of Photo-Induced Discoloration on Wood Treated with the Polyphenols from Acacia Confusa Heartwood

Abstract

Previous studies have clearly demonstrated that the polyphenols of the ethyl acetate (EtOAc) fraction in the heartwood extract from Acacia confusa (AcHWE) had good photostabilities to prevent photodegradation of wood. The wood photostabilizing actions of condensed tannins and flavonoids from the EtOAc fraction in AcHWE have been individually established, but the effects of these polyphenols on photo-induced discoloration are unknown and merit investigation. The results of this study showed that the six sub-fractions (EA1–EA6), which were fractionated from the EtOAc fraction in AcHWE and contained various condensed tannins and flavonoids, caused different photo-induced discoloration of treated wood. Treating the wood with abundant condensed tannins with little or no flavones and flavonols gave a dramatic dark reddish discoloration after irradiation. Treating the wood with abundant flavones and flavonols with/without condensed tannins produced a moderate dark reddish discoloration with faded yellow tone after irradiation. However, if there are abundant flavanones in the treated wood, their flavanones could transform to chalcones, which increased the yellow tone of treated wood surfaces after initial irradiation. These results illustrated explicit discoloration tendencies for polyphenols in the photodegradation processes for wood and can be the references for further applications.