Antioxidant properties of wood extracts and colour stability of woods

Abstract

-Industrial wood extracts were selected and other extracts were prepared in the laboratory from some chosen wood species. Antioxidant capacities of extracts were measured by three methods: the oxygen uptake method, the kinetic DPPH method, and the equilibrium DPPH method. There is a fair correlation between the three methods. Total phenol contents of the extracts and colour stability of woods were measured. For the same phenol content, extracts containing condensed tannins are more antioxidant than those containing hydrolysable tannins. Colour stability is clearly correlated neither with phenol content nor with antioxidant capacity of the extracts, but it is conferred to non durable woods if impregnated with extracts of durable species. Light aging is accompanied by consumption of the most antioxidant compounds of the extracts first.colour / wood /extract / tannin / antioxidant / polyphenol Résumé -Les propriétés antioxydantes d'extraits de bois et la stabilité de la couleur de ces bois. Nous avons étudié des extraits industriels de bois et préparé au laboratoire les extraits de quelques essences. Nous avons mesuré le pouvoir antioxydant des extraits par trois méthodes : la mesure de la consommation d'oxygène, et deux méthodes utilisant le DPPH, l'une cinétique et l'autre à l'équilibre. Les résultats obtenus par les trois méthodes sont raisonnablement corrélés. Nous avons mesuré le contenu phénolique total des extraits et la durabilité de la couleur des bois correspondants. Pour le même contenu phénolique, les extraits contenant des tannins condensés sont plus antioxydants que ceux contenant des tannins hydrolysables. La durabilité de la couleur n'est clairement corrélée ni avec le contenu phénolique ni avec le pouvoir antioxydant des extraits ; mais des extraits d'essences durables la confèrent à des essences peu durables. L'exposition à la lumière s'accompagne d'une consommation préférentielle des composés des extraits les plus antioxydants.couleur / bois / extrait / tanin / antioxydant / polyphénol

Comparison of phenolic extracts obtained of Pinus radiata bark from pulp and paper industry and sawmill industry

“…The maximum yield obtained in this study was low and similar to other reported for Pinus radiata bark (2.0 %); although, with different operating conditions (extraction time 24 h and, solvent Met OH/H 2 O (7:3 % v/v)) (Diouf et al 2006). Using more aggressive conditions (NaOH/H 2 O 1%, 100ºC), Ku and Mun (2007) increased ten times the yield.…”

“…Considering the differences in the extraction method, quantification methodology and data reports, it is difficult to compare our results with values obtained for Pinus radiata bark extracts in other studies. Still, total phenols content was found to be higher than the values obtained for other Pinus radiata analyzed with the same analytical method (Diouf et al 2006, Raghavendra et al 2007). …”

Antioxidant activity of phenolic extracts from chestnut fruit and forest industries residues

“…Except for lime wood, the lowest extraction yields were obtained for the water extractions and the highest for the extractions carried out with an aqueous solution of 1 % sodium hydroxide and 1 % sodium sulphite. Significantly lower extraction yields (2-14.7 %) were obtained for wood and bark extracted with methanol/water 70:30 (v/v) (Diouf et al 2006), and it is noteworthy that the lowest value corresponded to pine bark. Although a high extraction yield is important in terms of process economic viability, it must be accompanied by extracts with high values of those properties related to prevent wood photodegradation, as is the case for extract antioxidant activity which was evaluated by different methods.…”

“…Using ESR spectroscopy it was demonstrated that wood radicals induced by UV light were inhibited by Acacia confusa heartwood extracts and consequently wood photodegradation was retarded (Chang et al 2014). Diouf et al (2006) found that wood species with low antioxidant capacity happened to be less colour durable, whereas those with high antioxidant capacity were more light resistant. Additionally, color stability was conferred to non durable woods if impregnated with extracts of durable species.…”

EFFECT OF THE BENCH SCALE EXTRACTION CONDITIONS ON Pinus radiata BARK EXTRACT YIELD, ANTIOXIDANT PROPERTIES AND COMPOSITION

“…Indeed, Jerez et al (2006Jerez et al ( , 2007b, Ku et al (2007) and Diouf et al (2006) used 0.16 L reactors, 0.25 L extractors and 22 cm 3 cells, respectively;…”