Influences of merbau heartwood extracts and their metal complexes on wood photodegradation
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ORIGINAL
Influences of merbau heartwood extracts and their metal complexes on wood photodegradation Nien‑Chih Hsiao1 · Tzu‑Cheng Chang2 · Shang‑Tzen Chang1 Received: 29 February 2020 / Accepted: 16 September 2020 © Springer-Verlag GmbH Germany, part of Springer Nature 2020
Abstract Merbau (Intsia spp.) heartwood is a highly valued commercial wood but has problems with extractive bleeding when used as a construction material outdoors. The metal complexation method is one solution to resolve this problem. However, properties of merbau heartwood extracts would be modified and the anti-weathering ability changed. This study investigates the wood photo-protection ability of the merbau heartwood extract and its metal complexes. The results reveal that merbau heartwood extract has good free radical scavenging ability and UV absorptivity, which could inhibit wood photodegradation. After metal complexation, the extract-metal complexes also have wood photo-protection ability that inhibits wood photodegradation. Furthermore, since catecholic phenols were chelated by iron(II)/copper(II), the oxidative derivatives were consequently inhibited. Accordingly, these findings show that both merbau heartwood extract and its metal complexes have the ability to remove photo-induced hazards and enhance wood photostability for short periods of UV irradiation. Additionally, these results can be a reference for the environmentally benign utilization of merbau heartwood.
1 Introduction Wood is a bio-material composed of cellulose, hemicellulose and lignin. Since wood is easily processed and has attractive color and texture, it is extensively applied in many fields. However, because lignin is composed of many chromophores, it can be readily degraded by UV light, shortening its life cycle (Müller et al. 2003; Pandey 2005). Many studies (Crestini and D’Auria 1997; Bonini et al. 1998; Fischer and Beyer 2000; Min and Boff 2002; Chang and Chang 2018) have shown that reaction hazards, such as free radicals and singlet oxygen, produced during photodegradation, can accelerate its degradation. To retard degradation, photostabilizers are often introduced into wood products. Chang and Chang (2018) found that flavonoids and condensed tannins can inhibit wood photodegradation. In addition, the presence of catechol units in the flavonoids or condensed tannins * Shang‑Tzen Chang [email protected] 1
School of Forestry and Resource Conservation, National Taiwan University, No. 1, Section 4, Roosevelt Road, Taipei 106, Taiwan
Department of Forestry and Natural Resources, National Ilan University, No.1, Section 1, Shennong Road., Yilan City 260, Yilan County, Taiwan
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can effectively remove the free radicals and singlet oxygen (Tournaire et al. 1993; Cren-Olivé et al. 2002; McPhail et al. 2003; Mukai et al. 2005; Nagai et al. 2005; Huvaere and Skibsted 2015). Flavones and flavonols can also effectively absorb UV light between 280 and 400 nm, reducing lignin photodegradation (Tattini et al. 2004; Huvaere and Skibsted 2015; Chang and Chang 2018). Fur
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