Linda Nisula | Åbo Akademi (original) (raw)

Papers by Linda Nisula

Research paper thumbnail of Knots in trees – A new rich source of lignans

Phytochemistry Reviews, 2000

Recent research in our group has revealed that knots, i.e. the branch bases inside tree stems, co... more Recent research in our group has revealed that knots, i.e. the branch bases inside tree stems, commonly contain 5-10% (w/w) of lignans. Norway spruce (Picea abies) knots contain as much as 6-24% of lignans, with 7hydroxymatairesinol (HMR) as the predominant (70-85%) lignan. Some other spruce species also contain HMR as the main lignan, but some spruce species have also other dominating lignans. Most fir (Abies) species contain secoisolariciresinol and lariciresinol as the main lignans. Lignans occur also in knots of pines (Pinus spp.), although in lower amounts than in spruces and firs. Scots pine (Pinus silvestris) knots were found to contain 0.4-3% of lignans with nortrachelogenin as the main lignan. Lignans have been identified also in knots of some hardwoods, although flavonoids are more abundant in hardwoods. Knots are detrimental in the manufacture of pulp and paper and should preferably be removed before pulping. This is possible using a recently developed industrially applicable process called ChipSep. Recent research has also established novel synthetic routes to several lignans, such as matairesinol, secoisolariciresinol, lariciresinol and cyclolariciresinol, starting from hydroxymatairesinol by applying fairly straight-forward chemical transformations. We conclude that wood knots in certain spruce and fir species constitute the richest known source of lignans in nature. The lignans occur in knots in free form and are easily extracted by aqueous ethanol, or even by water. Not only HMR, but also other potentially valuable lignans, could be produced in a scale of hundreds of tons per year by extraction of knots separated from wood chips at pulp and paper mills.

Research paper thumbnail of Isolation of flavonoids from aspen knotwood by pressurized hot water extraction and comparison with other extraction techniques

Talanta, 2007

Pressurized hot water extraction (PHWE) conditions (time, temperature, pressure) were optimized f... more Pressurized hot water extraction (PHWE) conditions (time, temperature, pressure) were optimized for the extraction of naringenin and other major flavonoids (dihydrokaempferol, naringin) from knotwood of aspen. Extracts were analysed by GC-FID, GC-MS, HPLC-UV and HPLC-MS. The results were compared with those obtained by Soxhlet, ultrasonic extraction and reflux in methanol. Flavonoids were most efficiently extracted with PHWE at 150 • C and 220 bar with 35 min extraction time. Soxhlet with methanol gave slightly higher recoveries, but an extraction time of 48 h was required. Naringenin concentration was highest in knotwood (1.15% dry weight) and much lower in the sapwood. PHWE proved to be cheap, fast and effective for the isolation of biofunctional flavonoids from aspen knotwood, producing higher recoveries than 24 h Soxhlet extraction, sonication or 24 h reflux.

Research paper thumbnail of Knots in Trees: A Rich Source of Bioactive Polyphenols

ACS Symposium Series, 2007

Research paper thumbnail of Knots in trees – A new rich source of lignans

Phytochemistry Reviews, 2000

Recent research in our group has revealed that knots, i.e. the branch bases inside tree stems, co... more Recent research in our group has revealed that knots, i.e. the branch bases inside tree stems, commonly contain 5-10% (w/w) of lignans. Norway spruce (Picea abies) knots contain as much as 6-24% of lignans, with 7hydroxymatairesinol (HMR) as the predominant (70-85%) lignan. Some other spruce species also contain HMR as the main lignan, but some spruce species have also other dominating lignans. Most fir (Abies) species contain secoisolariciresinol and lariciresinol as the main lignans. Lignans occur also in knots of pines (Pinus spp.), although in lower amounts than in spruces and firs. Scots pine (Pinus silvestris) knots were found to contain 0.4-3% of lignans with nortrachelogenin as the main lignan. Lignans have been identified also in knots of some hardwoods, although flavonoids are more abundant in hardwoods. Knots are detrimental in the manufacture of pulp and paper and should preferably be removed before pulping. This is possible using a recently developed industrially applicable process called ChipSep. Recent research has also established novel synthetic routes to several lignans, such as matairesinol, secoisolariciresinol, lariciresinol and cyclolariciresinol, starting from hydroxymatairesinol by applying fairly straight-forward chemical transformations. We conclude that wood knots in certain spruce and fir species constitute the richest known source of lignans in nature. The lignans occur in knots in free form and are easily extracted by aqueous ethanol, or even by water. Not only HMR, but also other potentially valuable lignans, could be produced in a scale of hundreds of tons per year by extraction of knots separated from wood chips at pulp and paper mills.

Research paper thumbnail of Bioactive phenolic substances in industrially important tree species. Part 1: Knots and stemwood of different spruce species

Holzforschung, 2000

ABSTRACT Knots, i.e. branch bases inside tree stems, in fir trees contained remarkably higher con... more ABSTRACT Knots, i.e. branch bases inside tree stems, in fir trees contained remarkably higher concentrations of lignans, oligolignans, and juvabiones than the adjacent stemwood. Eight fir species were analysed (Abies sibirica, A. lasiocarpa, A. balsamea, A. alba, A. amabilis, A. veitchii, A. sachalinensis, and A. concolor). The amount of lignans could in some knots exceeds 6% (w/w) and the knots generally contained 2050 times more lignans than the stemwood. However, there were large variations, not only between species but also even between knots in the same tree. Secoisolariciresinol was the predominant lignan in all knots. The lignans occur in free form in the knots and are easily extracted with polar solvents. In addition to the lignans, oligomeric aromatic substances, mainly sesquineo and dineolignans, and juvabiones were accumulated in the knotwood. Secoisolariciresinol, but also lariciresinol (Abies alba) and 7-hydroxymatairesinol (A. amabilis), could be extracted in large scale from fir knots at pulp and paper mills. The ready availability of large amounts of lignans and oligolignans now enables research to assess their bioactivity and provide the base for applications in medicine and nutrition, or as natural antioxidants and antimicrobial agents in various technical products.

Books by Linda Nisula

Research paper thumbnail of Wood Extractives in Conifers - A Study of Stemwood and Knots of Industrially Important Species

Study of lipophilic and hydrophilic extractives in heartwood, sapwood and knots of 39 industriall... more Study of lipophilic and hydrophilic extractives in heartwood, sapwood and knots of 39 industrially important conifer species: 14 pines (Pinus), 7 spruces (Picea), 9 firs (Abies), 5 larches (Larix), 3 hemlocks (Tsuga) and Douglas-fir (Pseudotsuga).

The wood samples were sequentially extracted, and the amount and composition of resin acids, fatty acids, sterols, steryl esters, acylglycerols, juvabiones, lignans, oligolignans, flavonoids and stilbenes were analysed by gas chromatography (GC) and GC-mass spectrometry.

Research paper thumbnail of Knots in trees – A new rich source of lignans

Phytochemistry Reviews, 2000

Recent research in our group has revealed that knots, i.e. the branch bases inside tree stems, co... more Recent research in our group has revealed that knots, i.e. the branch bases inside tree stems, commonly contain 5-10% (w/w) of lignans. Norway spruce (Picea abies) knots contain as much as 6-24% of lignans, with 7hydroxymatairesinol (HMR) as the predominant (70-85%) lignan. Some other spruce species also contain HMR as the main lignan, but some spruce species have also other dominating lignans. Most fir (Abies) species contain secoisolariciresinol and lariciresinol as the main lignans. Lignans occur also in knots of pines (Pinus spp.), although in lower amounts than in spruces and firs. Scots pine (Pinus silvestris) knots were found to contain 0.4-3% of lignans with nortrachelogenin as the main lignan. Lignans have been identified also in knots of some hardwoods, although flavonoids are more abundant in hardwoods. Knots are detrimental in the manufacture of pulp and paper and should preferably be removed before pulping. This is possible using a recently developed industrially applicable process called ChipSep. Recent research has also established novel synthetic routes to several lignans, such as matairesinol, secoisolariciresinol, lariciresinol and cyclolariciresinol, starting from hydroxymatairesinol by applying fairly straight-forward chemical transformations. We conclude that wood knots in certain spruce and fir species constitute the richest known source of lignans in nature. The lignans occur in knots in free form and are easily extracted by aqueous ethanol, or even by water. Not only HMR, but also other potentially valuable lignans, could be produced in a scale of hundreds of tons per year by extraction of knots separated from wood chips at pulp and paper mills.

Research paper thumbnail of Isolation of flavonoids from aspen knotwood by pressurized hot water extraction and comparison with other extraction techniques

Talanta, 2007

Pressurized hot water extraction (PHWE) conditions (time, temperature, pressure) were optimized f... more Pressurized hot water extraction (PHWE) conditions (time, temperature, pressure) were optimized for the extraction of naringenin and other major flavonoids (dihydrokaempferol, naringin) from knotwood of aspen. Extracts were analysed by GC-FID, GC-MS, HPLC-UV and HPLC-MS. The results were compared with those obtained by Soxhlet, ultrasonic extraction and reflux in methanol. Flavonoids were most efficiently extracted with PHWE at 150 • C and 220 bar with 35 min extraction time. Soxhlet with methanol gave slightly higher recoveries, but an extraction time of 48 h was required. Naringenin concentration was highest in knotwood (1.15% dry weight) and much lower in the sapwood. PHWE proved to be cheap, fast and effective for the isolation of biofunctional flavonoids from aspen knotwood, producing higher recoveries than 24 h Soxhlet extraction, sonication or 24 h reflux.

Research paper thumbnail of Knots in Trees: A Rich Source of Bioactive Polyphenols

ACS Symposium Series, 2007

Research paper thumbnail of Knots in trees – A new rich source of lignans

Phytochemistry Reviews, 2000

Recent research in our group has revealed that knots, i.e. the branch bases inside tree stems, co... more Recent research in our group has revealed that knots, i.e. the branch bases inside tree stems, commonly contain 5-10% (w/w) of lignans. Norway spruce (Picea abies) knots contain as much as 6-24% of lignans, with 7hydroxymatairesinol (HMR) as the predominant (70-85%) lignan. Some other spruce species also contain HMR as the main lignan, but some spruce species have also other dominating lignans. Most fir (Abies) species contain secoisolariciresinol and lariciresinol as the main lignans. Lignans occur also in knots of pines (Pinus spp.), although in lower amounts than in spruces and firs. Scots pine (Pinus silvestris) knots were found to contain 0.4-3% of lignans with nortrachelogenin as the main lignan. Lignans have been identified also in knots of some hardwoods, although flavonoids are more abundant in hardwoods. Knots are detrimental in the manufacture of pulp and paper and should preferably be removed before pulping. This is possible using a recently developed industrially applicable process called ChipSep. Recent research has also established novel synthetic routes to several lignans, such as matairesinol, secoisolariciresinol, lariciresinol and cyclolariciresinol, starting from hydroxymatairesinol by applying fairly straight-forward chemical transformations. We conclude that wood knots in certain spruce and fir species constitute the richest known source of lignans in nature. The lignans occur in knots in free form and are easily extracted by aqueous ethanol, or even by water. Not only HMR, but also other potentially valuable lignans, could be produced in a scale of hundreds of tons per year by extraction of knots separated from wood chips at pulp and paper mills.

Research paper thumbnail of Bioactive phenolic substances in industrially important tree species. Part 1: Knots and stemwood of different spruce species

Holzforschung, 2000

ABSTRACT Knots, i.e. branch bases inside tree stems, in fir trees contained remarkably higher con... more ABSTRACT Knots, i.e. branch bases inside tree stems, in fir trees contained remarkably higher concentrations of lignans, oligolignans, and juvabiones than the adjacent stemwood. Eight fir species were analysed (Abies sibirica, A. lasiocarpa, A. balsamea, A. alba, A. amabilis, A. veitchii, A. sachalinensis, and A. concolor). The amount of lignans could in some knots exceeds 6% (w/w) and the knots generally contained 2050 times more lignans than the stemwood. However, there were large variations, not only between species but also even between knots in the same tree. Secoisolariciresinol was the predominant lignan in all knots. The lignans occur in free form in the knots and are easily extracted with polar solvents. In addition to the lignans, oligomeric aromatic substances, mainly sesquineo and dineolignans, and juvabiones were accumulated in the knotwood. Secoisolariciresinol, but also lariciresinol (Abies alba) and 7-hydroxymatairesinol (A. amabilis), could be extracted in large scale from fir knots at pulp and paper mills. The ready availability of large amounts of lignans and oligolignans now enables research to assess their bioactivity and provide the base for applications in medicine and nutrition, or as natural antioxidants and antimicrobial agents in various technical products.

Research paper thumbnail of Wood Extractives in Conifers - A Study of Stemwood and Knots of Industrially Important Species

Study of lipophilic and hydrophilic extractives in heartwood, sapwood and knots of 39 industriall... more Study of lipophilic and hydrophilic extractives in heartwood, sapwood and knots of 39 industrially important conifer species: 14 pines (Pinus), 7 spruces (Picea), 9 firs (Abies), 5 larches (Larix), 3 hemlocks (Tsuga) and Douglas-fir (Pseudotsuga).

The wood samples were sequentially extracted, and the amount and composition of resin acids, fatty acids, sterols, steryl esters, acylglycerols, juvabiones, lignans, oligolignans, flavonoids and stilbenes were analysed by gas chromatography (GC) and GC-mass spectrometry.