Phenolic and Lipophilic Extractives in Scots Pine Knots and Stemwood

Abstract

The phenolic and lipophilic extractives in the heartwood of knots from seven Scots pine trees were analysed by GC, GC-MS and HPSEC. The knots contained large amounts of phenolic stilbenes, 1-7% (w/w), and lignans, 0.4-3% (w/w), while the stemwood contained around 1% (w/w) of stilbenes and no detectable lignans. In young trees without stem heartwood the stilbene content in the knots was up to 200 times that in the stem. Some in-tree and between-tree variation was seen in the content of phenolic compounds in the knots. The ratio of pinosylvin monomethyl ether to pinosylvin was higher in the knots than in the stemwood. The most abundant lignan was nortrachelogenin, but also matairesinol, secoisolariciresinol and liovil were present in small amounts in the knots. The knots also contained a complex mixture of lignan-like compounds, here called oligolignans. The flavonoid pinocembrin was present in both stemwood and knots in amounts below 0.02% (w/w). The stilbene concentration in the radial direction, from the pith to the outer branch, decreased or was on the same level inside the stem, while it decreased markedly in the outer branch. The lignan concentration was on the same level or decreased slightly inside the stem, while it decreased markedly in the branches and became almost non-existent within 10 cm out in the branches. The knots contained large amounts (4.5-32% (w/w)) of lipophilic extractives, mainly resin acids. Some in-tree and between-tree variation was seen for the resin acids. The abietanetype resin acids dominated over the pimarane-type acids and abietic acid was the most abundant resin acid in the knots and in stem heartwood. The amount of resin acids in the radial direction decreased or was on the same level inside the stem, while a clear decrease was detected in the branches. The profile of the distribution of resin acids and phenolic compounds was similar. The knots also contained up to 0.5% (w/w) of diterpenyl aldehydes.

Screening Analyses of Pinosylvin Stilbenes, Resin Acids and Lignans in Norwegian Conifers

“…Another recent detailed study of Scots pine knots and stemwood detected large amounts of phenolic stilbenes, 1-7 % (w/w) in the knots, while the stemwood contained less than 1% (w/w) [19]. The trees were collected in northern and southern Finland.…”

“…The trees were collected in northern and southern Finland. Because of the large amounts of pinosylvins in pine, it has been suggested that other important species like spruce (Picea abies) should be analysed for its potential pinosylvin content [19].…”

“…Lignans (0.4-3 % w/w) have been reported in pine knots, while no detectable amounts were found in the stemwood. As for resin acids, the knots contained large amounts (4.5-30 % w/w) and the stemwood minor amounts [19]. Lignans are found in large amounts (6-24% w/w), in Finnish spruce knots; with hydroxymatairesinol (HMR, Scheme 1) comprising 65-85% of these lignans.…”

“…Since quite large in-treeand between-tree variations have been reported in previous extensive studies [19], we limited our analyses to two pine trees of different ages (87 and 34 years) to examine whether the content and distribution of pinosylvins in these Norwegian trees were within the previously reported ranges for Finnish pine. Table 1.…”

Fiber Surface and Paper Technical Properties of Eucalyptus globulus and Eucalyptus nitens Pulps after Modified Cooking and Bleaching

“…However, relatively high amounts of extractives can be found in heartwood and knots in softwoods (Willför et al 2003). The process used for kraft pulp manufacturing significantly affects the amount and distribution of extractives, which influence the interactions of fibers in the bleaching and papermaking processes (Fardim et al 2005).…”