The Effects of Adding Heartwood Extractives from Acacia confusa on the Lightfastness Improvement of Refined Oriental Lacquer

In this study, a renewable polymeric material, refined oriental lacquer (ROL), used as a wood protective coating, and the Acacia confusa Merr. heartwood extractive, which was added as a natural photostabilizer for improving the lightfastness of ROL, were investigated. The best extract conditions for preparing heartwood extractives and the most suitable amount of addition (0, 1, 3, 5, and 10 phr) were investigated. The lightfastness index including brightness difference (ΔL *), yellowness difference (ΔYI), and color difference (ΔE *), and their applied properties of coating and film were measured. In the manufacture of heartwood extractives, the yield of extractives with acetone solvent was 9.2%, which was higher than that from toluene/ethanol solvent of 2.6%, and also had the most abundant total phenolic contents (535.2 mgGAE/g) and total flavonoid contents (252.3 μgRE/g). According to the SEM inspection and FTIR analysis, the plant gums migration to the surface of films and cracks occurred after UV exposure. The phenomena for photodegradation of ROL films were reduced after the addition of heartwood extractives. Among the different amounts of the heartwood extractives, the 10 phr addition was the best choice; however, the 1 phr heartwood extractive addition already showed noticeable lightfastness improvement. The drying times of ROL were extended and film performances worse with higher additions of heartwood extractives. Among the ROL films with different heartwood extractive additions, the ROL film with 1 phr addition had superior films properties, regarding adhesion and thermal stability, compared with the films of raw oriental lacquer.

Extractive distribution in Pseudotsuga menziesii: effects on cell wall porosity in sapwood and heartwood

ABSTRACT Douglas-fir (Pseudotsuga menziesii) has distinctly colored heartwood as a result of extractive deposition during heartwood formation. This is known to affect natural durability and treatability with preservatives, as well as other types of wood modification involving infiltration with chemicals. The distribution of extractives in sapwood and heartwood of Douglas-fir was studied using fluorescence microscopy. Several different types of extractive including flavonoids, resin acids, and tannins were localized to heartwood cell walls, resin canals, and rays, using autofluorescence or staining of flavonoids with Naturstoff A reagent. Extractives were found to infiltrate the cell walls of heartwood tracheids and were also present to a lesser extent in sapwood tracheid cell walls, especially in regions adjacent to the resin canals. Förster resonance energy transfer measurements showed that the accessibility of lignin lining cell wall micropores to rhodamine dye was reduced by about 50%, probably as a result of cell wall-bound tannin-like materials which accumulate in heartwood relative to sapwood, and are responsible for the orange color of the heartwood. These results indicate that micro-distribution of heartwood extractives affects cell wall porosity which is reduced by the accumulation of heartwood extractives in softwood tracheid cell walls.

Isolation and structural elucidation of heartwood extractives of Juglans sigillata

Juglans sigillata is a deciduous tree in Juglandaceae that grows native in southwestern China. The extracts of J. sigillata are used extensively in folk medicines to treat or prevent various diseases. However, the individual components of J. sigillata heartwood are not known. In this work, the following substances have been isolated from the heartwood: a new trans-feruloyl isoflavone glycoside, namely 3′-methoxy-5′-hydroxy-isoflavone-7-O-(4′′-trans-feruloyl)-β-D-glucoyranoside (I), a known isoflavone glucoside, i.e. 3′-methoxy-5′-hydroxy-isoflavone-7-O-β-D-glucoyranoside (II), and two known flavonol glycosides: kaempferol-3-O-α-L-rhamnopyranoside (III) and myricetin-3-O-α-L-rhamnopyranoside (IV). Chemical structures of extractives I~IV were elucidated mainly based on their spectroscopic [nuclear magnetic resonance (NMR), mass spectroscopy (MS), ultraviolet (UV) and infrared (IR)] and chemical analysis, as well as by comparison with literature data. Compound I was never isolated from any other plant, and it is described the first time in this work. Compound II was not found before in extracts of the genus Juglans, and the compounds III and IV are the first time described as components of J. sigillata extractives.