The Experts below are selected from a list of 2565 Experts worldwide ranked by ideXlab platform
Kalevi Pihlaja - One of the best experts on this subject based on the ideXlab platform.
-
defensive effect of surface flavonoid aglycones of Betula pubescens leaves against first instar epirrita autumnata larvae
Journal of Chemical Ecology, 2004Co-Authors: Maria Lahtinen, Lauri Kapari, Kyosti Lempa, Elena Valkama, Erkki Haukioja, Vladimir Ossipov, Jari Sinkkonen, Juha-pekka Salminen, Kalevi PihlajaAbstract:The surface of birch leaves contains glandular trichomes that secrete exudates containing flavonoid aglycones. We investigated the biological activities of white birch (Betula pubescens) leaf surface exudates against larvae of the autumnal moth, Epirrita autumnata, a common insect pest of birch. We found that tree-specific mortality (up to 100%) of first instar larvae correlated strongly with the tree-specific contents of surface flavonoid aglycones (rs=0.905) in emerging leaves. We also found that first instars clearly preferred birch buds from which surface exudates had been removed. In addition, the duration of the first instar was shortened by 29%, and the weights and relative growth rates of first instars improved by 8% and 52%, respectively, as a result of removal of the exudates from their leaf diet. The correlation of tree-specific foliar contents of flavonoid aglycones, especially 5-hydroxy-4',7-dimethoxyflavanone, with changes in larval performance, suggests that flavonoid aglycones are responsible for the changes observed in first instar larval performance. The results show that chemical characteristics of birch leaves are effective against neonate E. autumnata larvae. However, the removal of leaf surface exudates from fully expanded leaves did not affect the leaf acceptance for the voracious fifth instars. This is probably a result of reduction in contents of flavonoid aglycones compared to those of emerging leaves.
-
new sesquiterpenoid type bicyclic compounds from the buds of Betula pubescens ring contracted products of β caryophyllene
European Journal of Organic Chemistry, 2004Co-Authors: Karel D Klika, Juha-pekka Salminen, Betul Demirci, Vladimir V Ovcharenko, Satu Vuorela, Husnu Can K Baser, Kalevi PihlajaAbstract:The essential oils obtained from the buds of Betula pubescens ssp. pubescens and B. pubescens ssp. czerepanovii were analyzed both by GC and GC/MS and, of the 31 compounds identified, 14-acetoxy-β-caryophyllene was determined to be the main component in both oils in addition to 25 other previously known compounds. Three of the compounds were isolated from the oils and further characterized by NMR spectroscopy and mass spectrometry, including a new bicyclic aldehyde (4,8,8-trimethyl-2-methylenebicyclo[5.2.0]nonane-4-carbaldehyde, birkenal), a new tricyclic lactone (1,4,4,8-tetramethyl-10-oxatricyclo[6.2.1.02,5]undecan-9-one, hushinone), and the recently described 6-hydroxycaryophyllene. The isolation of birkenal also enabled identification of its corresponding alcohol {(4,8,8-trimethyl-2-methylenebicyclo[5.2.0]non-4-yl)methanol, birkenol} and the acetate of this alcohol {(4,8,8-trimethyl-2-methylenebicyclo[5.2.0]non-4-yl)methyl acetate, birkenyl acetate}, both of which are also novel compounds and are present in the two essential oils. These new compounds, bearing evident sesquiterpenoid traits, potentially arise biosynthetically as ring-contracted products of β-caryophyllene or a derivative thereof. The fifth novel compound present in the oils was determined to be the acetate of 6-hydroxycaryophyllene. The preferred conformations of the seven- or nine-membered rings in these structures were also determined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
-
Seasonal variation in the content of hydrolysable tannins in leaves of Betula pubescens.
Phytochemistry, 2001Co-Authors: Juha-pekka Salminen, Erkki Haukioja, Vladimir Ossipov, Kalevi PihlajaAbstract:The contents of 13 hydrolysable tannins in the leaves of white birch (Betula pubescens L.) trees were analysed at twelve stages throughout the growing season. All individual galloylglucoses, from 1-O-galloyl-beta-D-glucopyranose to 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranose, accumulated in young leaves, while ellagitannins showed significantly variable seasonal trends. The major ellagitannin during the whole growing season was pedunculagin while 2,3-(S)-HHDP-glucopyranose. the end product of the proposed ellagitannin pathway, accumulated in mature leaves. Relationships between the characteristics of seasonal variation in the contents of individual ellagitannins and their chemical structures were used to unravel the biogenesis of ellagitannins in birch leaves. Evidence of degradation of ellagitannins through hydrolysis during leaf growth and development is presented and implications for herbivory are discussed.
-
characterisation of hydrolysable tannins from leaves of Betula pubescens by high performance liquid chromatography mass spectrometry
Journal of Chromatography A, 1999Co-Authors: Juha-pekka Salminen, Erkki Haukioja, Vladimir Ossipov, Jyrki Loponen, Kalevi PihlajaAbstract:Abstract A high-performance liquid chromatography–electrospray ionisation mass spectrometry (HPLC–ESI-MS) method, assisted by diode array detection, for the characterisation of individual hydrolysable tannins in birch leaves was developed. With the method, it was found that birch ( Betula pubescens ) leaves contained an exceptionally complex mixture of hydrolysable tannins; 14 gallotannins and 20 ellagitannins were identified. The developed HPLC–ESI-MS method allows the qualitative and quantitative determination of individual gallotannins and ellagitannins directly from crude birch leaf extract. This is important in studying ecological functions of these phenolic compounds, especially their role in the resistance of birch leaves against insects.
-
Gallotannins of birch Betula pubescens leaves: HLPC separation and quantification
Biochemical Systematics and Ecology, 1997Co-Authors: Vladimir Ossipov, Svetlana Ossipova, Erkki Haukioja, Jyrki Loponen, Kalevi PihlajaAbstract:Abstract High concentrations of gallotannins were found in young leaves of mountain birch trees ( Betula pubescens ssp. tortuosa ). Phenolic compounds were separated by H PLC and their UV spectra were recorded with a diode array detector. On the basis of these data, 11 individual gallotannins were preliminary identified in birch leaves. Strong and positive correlations were found between concentrations of these gallotannins and the protein precipitation capacity of extracts. Content of gallotannins decreased rapidly with leaf growth and maturation. Among-tree variation was high and significant for most individual gallotannins. Intracellular organization and metabolism of gallotannins in birch leaves are discussed.
Vladimir Ossipov - One of the best experts on this subject based on the ideXlab platform.
-
Effects of three years’ increase in density of the geometrid Epirrita autumnata on the change in metabolome of mountain birch trees (Betula pubescens ssp. czerepanovii)
Chemoecology, 2014Co-Authors: Vladimir Ossipov, Tero Klemola, Kai Ruohomäki, Juha-pekka SalminenAbstract:The principal objective of the study was to characterize effects of increasing density of the autumnal moth, Epirrita autumnata (Lepidoptera, Geometridae), for 3 successive years on the change in metabolome of mountain birch trees ( Betula pubescens ssp . czerepanovii ). During the three study years (2000–2002), the larval density varied from low to very high (outbreak) density. Samples of leaves were collected from the same 12 trees at the same phenological stage of the trees each year. The leaves were collected from undamaged trees in the first year, from trees slightly damaged by larvae in the second year, and from trees heavily damaged by larvae in the third year. Metabolome analysis showed that the increase in density of E. autumnata larvae and degree of damage of birch trees caused multiple biochemical changes in the leaves, including increased concentrations of phenolic compounds (proanthocyanidins and hydrolysable tannins) and reduced concentrations of nutritive metabolites (monosaccharides, amino acids and some organic acids). These changes reduced the quality of leaves as food for larvae and, probably, were associated with induced chemical resistance of the birches to herbivorous insects. Additionally, the concentration of α-tocopherol was significantly higher in both slightly and heavily damaged trees. Mechanisms of changes in the metabolism of phenolic compounds and carbohydrates, and the role of α-tocopherol in their regulation are discussed.
-
defensive effect of surface flavonoid aglycones of Betula pubescens leaves against first instar epirrita autumnata larvae
Journal of Chemical Ecology, 2004Co-Authors: Maria Lahtinen, Lauri Kapari, Kyosti Lempa, Elena Valkama, Erkki Haukioja, Vladimir Ossipov, Jari Sinkkonen, Juha-pekka Salminen, Kalevi PihlajaAbstract:The surface of birch leaves contains glandular trichomes that secrete exudates containing flavonoid aglycones. We investigated the biological activities of white birch (Betula pubescens) leaf surface exudates against larvae of the autumnal moth, Epirrita autumnata, a common insect pest of birch. We found that tree-specific mortality (up to 100%) of first instar larvae correlated strongly with the tree-specific contents of surface flavonoid aglycones (rs=0.905) in emerging leaves. We also found that first instars clearly preferred birch buds from which surface exudates had been removed. In addition, the duration of the first instar was shortened by 29%, and the weights and relative growth rates of first instars improved by 8% and 52%, respectively, as a result of removal of the exudates from their leaf diet. The correlation of tree-specific foliar contents of flavonoid aglycones, especially 5-hydroxy-4',7-dimethoxyflavanone, with changes in larval performance, suggests that flavonoid aglycones are responsible for the changes observed in first instar larval performance. The results show that chemical characteristics of birch leaves are effective against neonate E. autumnata larvae. However, the removal of leaf surface exudates from fully expanded leaves did not affect the leaf acceptance for the voracious fifth instars. This is probably a result of reduction in contents of flavonoid aglycones compared to those of emerging leaves.
-
Seasonal variation in the content of hydrolysable tannins in leaves of Betula pubescens.
Phytochemistry, 2001Co-Authors: Juha-pekka Salminen, Erkki Haukioja, Vladimir Ossipov, Kalevi PihlajaAbstract:The contents of 13 hydrolysable tannins in the leaves of white birch (Betula pubescens L.) trees were analysed at twelve stages throughout the growing season. All individual galloylglucoses, from 1-O-galloyl-beta-D-glucopyranose to 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranose, accumulated in young leaves, while ellagitannins showed significantly variable seasonal trends. The major ellagitannin during the whole growing season was pedunculagin while 2,3-(S)-HHDP-glucopyranose. the end product of the proposed ellagitannin pathway, accumulated in mature leaves. Relationships between the characteristics of seasonal variation in the contents of individual ellagitannins and their chemical structures were used to unravel the biogenesis of ellagitannins in birch leaves. Evidence of degradation of ellagitannins through hydrolysis during leaf growth and development is presented and implications for herbivory are discussed.
-
characterisation of hydrolysable tannins from leaves of Betula pubescens by high performance liquid chromatography mass spectrometry
Journal of Chromatography A, 1999Co-Authors: Juha-pekka Salminen, Erkki Haukioja, Vladimir Ossipov, Jyrki Loponen, Kalevi PihlajaAbstract:Abstract A high-performance liquid chromatography–electrospray ionisation mass spectrometry (HPLC–ESI-MS) method, assisted by diode array detection, for the characterisation of individual hydrolysable tannins in birch leaves was developed. With the method, it was found that birch ( Betula pubescens ) leaves contained an exceptionally complex mixture of hydrolysable tannins; 14 gallotannins and 20 ellagitannins were identified. The developed HPLC–ESI-MS method allows the qualitative and quantitative determination of individual gallotannins and ellagitannins directly from crude birch leaf extract. This is important in studying ecological functions of these phenolic compounds, especially their role in the resistance of birch leaves against insects.
-
Gallotannins of birch Betula pubescens leaves: HLPC separation and quantification
Biochemical Systematics and Ecology, 1997Co-Authors: Vladimir Ossipov, Svetlana Ossipova, Erkki Haukioja, Jyrki Loponen, Kalevi PihlajaAbstract:Abstract High concentrations of gallotannins were found in young leaves of mountain birch trees ( Betula pubescens ssp. tortuosa ). Phenolic compounds were separated by H PLC and their UV spectra were recorded with a diode array detector. On the basis of these data, 11 individual gallotannins were preliminary identified in birch leaves. Strong and positive correlations were found between concentrations of these gallotannins and the protein precipitation capacity of extracts. Content of gallotannins decreased rapidly with leaf growth and maturation. Among-tree variation was high and significant for most individual gallotannins. Intracellular organization and metabolism of gallotannins in birch leaves are discussed.
Peter Groom - One of the best experts on this subject based on the ideXlab platform.
-
The aceramic production of Betula pubescens (downy birch) bark tar using simple raised structures. A viable Neanderthal technique
Archaeological and Anthropological Sciences, 2016Co-Authors: Tine Schenck, Peter GroomAbstract:Following on from our previous research into the prehistoric aceramic distillation and production of birch bark tar, this series of exploratory experiments investigated the use of raised structures within a fire. These field-based experiments were conducted using sand, gravel, wood fuel, and bark from Betula pubescens (downy birch). The structures that were created were simple raised sand mounds, which reflected known Neanderthal combustion surfaces from the Middle Palaeolithic. The bulk of the experiments were recorded throughout using a thermocouple to provide temperature readings from the base of the bark pyrolysis chamber. The experiments proved successful at producing birch bark tar and several containers were used to catch the tar for later analysis. Based on the results, the authors contend that not only could Neanderthals control fire but that regular birch bark tar production by Neanderthals was most likely a result of specific chaines operatoires in order to provide the necessary control and outcomes.
-
Experimental explorations into the aceramic dry distillation of Betula pubescens (downy birch) bark tar
Archaeological and Anthropological Sciences, 2015Co-Authors: Peter Groom, Tine Schenck, Grethe Moéll PedersenAbstract:A range of experiments were conducted in an attempt to create tar from the bark of Betula pubescens (downy birch) using an aceramic dry distillation process. Fire structures based on small pits and small kiln-like mounds were explored with a focus on fire intensities and differing burn times under field-based conditions. Heat penetration presented itself as an all-important factor, and the depth of the construction of the structures and features was considered to directly correlate to the impact of the heat. Single variable experiments confirmed that the necessary reducing atmosphere was achievable despite friable soil, but that heat would not penetrate a 50- to 80-mm-deep layer of grass turf. The evolution of structures from pits towards a raised type resulted in kiln-like structures which proved more successful. Though the experiments did not successfully produce tar as a finished product, they did lead to a better understanding of the dry distillation process of the established technology of birch bark tar extraction in aceramic societies.
Erkki Haukioja - One of the best experts on this subject based on the ideXlab platform.
-
defensive effect of surface flavonoid aglycones of Betula pubescens leaves against first instar epirrita autumnata larvae
Journal of Chemical Ecology, 2004Co-Authors: Maria Lahtinen, Lauri Kapari, Kyosti Lempa, Elena Valkama, Erkki Haukioja, Vladimir Ossipov, Jari Sinkkonen, Juha-pekka Salminen, Kalevi PihlajaAbstract:The surface of birch leaves contains glandular trichomes that secrete exudates containing flavonoid aglycones. We investigated the biological activities of white birch (Betula pubescens) leaf surface exudates against larvae of the autumnal moth, Epirrita autumnata, a common insect pest of birch. We found that tree-specific mortality (up to 100%) of first instar larvae correlated strongly with the tree-specific contents of surface flavonoid aglycones (rs=0.905) in emerging leaves. We also found that first instars clearly preferred birch buds from which surface exudates had been removed. In addition, the duration of the first instar was shortened by 29%, and the weights and relative growth rates of first instars improved by 8% and 52%, respectively, as a result of removal of the exudates from their leaf diet. The correlation of tree-specific foliar contents of flavonoid aglycones, especially 5-hydroxy-4',7-dimethoxyflavanone, with changes in larval performance, suggests that flavonoid aglycones are responsible for the changes observed in first instar larval performance. The results show that chemical characteristics of birch leaves are effective against neonate E. autumnata larvae. However, the removal of leaf surface exudates from fully expanded leaves did not affect the leaf acceptance for the voracious fifth instars. This is probably a result of reduction in contents of flavonoid aglycones compared to those of emerging leaves.
-
Seasonal variation in the content of hydrolysable tannins in leaves of Betula pubescens.
Phytochemistry, 2001Co-Authors: Juha-pekka Salminen, Erkki Haukioja, Vladimir Ossipov, Kalevi PihlajaAbstract:The contents of 13 hydrolysable tannins in the leaves of white birch (Betula pubescens L.) trees were analysed at twelve stages throughout the growing season. All individual galloylglucoses, from 1-O-galloyl-beta-D-glucopyranose to 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranose, accumulated in young leaves, while ellagitannins showed significantly variable seasonal trends. The major ellagitannin during the whole growing season was pedunculagin while 2,3-(S)-HHDP-glucopyranose. the end product of the proposed ellagitannin pathway, accumulated in mature leaves. Relationships between the characteristics of seasonal variation in the contents of individual ellagitannins and their chemical structures were used to unravel the biogenesis of ellagitannins in birch leaves. Evidence of degradation of ellagitannins through hydrolysis during leaf growth and development is presented and implications for herbivory are discussed.
-
characterisation of hydrolysable tannins from leaves of Betula pubescens by high performance liquid chromatography mass spectrometry
Journal of Chromatography A, 1999Co-Authors: Juha-pekka Salminen, Erkki Haukioja, Vladimir Ossipov, Jyrki Loponen, Kalevi PihlajaAbstract:Abstract A high-performance liquid chromatography–electrospray ionisation mass spectrometry (HPLC–ESI-MS) method, assisted by diode array detection, for the characterisation of individual hydrolysable tannins in birch leaves was developed. With the method, it was found that birch ( Betula pubescens ) leaves contained an exceptionally complex mixture of hydrolysable tannins; 14 gallotannins and 20 ellagitannins were identified. The developed HPLC–ESI-MS method allows the qualitative and quantitative determination of individual gallotannins and ellagitannins directly from crude birch leaf extract. This is important in studying ecological functions of these phenolic compounds, especially their role in the resistance of birch leaves against insects.
-
Gallotannins of birch Betula pubescens leaves: HLPC separation and quantification
Biochemical Systematics and Ecology, 1997Co-Authors: Vladimir Ossipov, Svetlana Ossipova, Erkki Haukioja, Jyrki Loponen, Kalevi PihlajaAbstract:Abstract High concentrations of gallotannins were found in young leaves of mountain birch trees ( Betula pubescens ssp. tortuosa ). Phenolic compounds were separated by H PLC and their UV spectra were recorded with a diode array detector. On the basis of these data, 11 individual gallotannins were preliminary identified in birch leaves. Strong and positive correlations were found between concentrations of these gallotannins and the protein precipitation capacity of extracts. Content of gallotannins decreased rapidly with leaf growth and maturation. Among-tree variation was high and significant for most individual gallotannins. Intracellular organization and metabolism of gallotannins in birch leaves are discussed.
-
Low molecular mass phenolics in foliage of Betula pubescens Ehrh. in relation to aerial pollution
Chemosphere, 1997Co-Authors: Jyrki Loponen, Erkki Haukioja, Vladimir Ossipov, Julia Koricheva, K. PihlajaaAbstract:Abstract Correlation between air pollution and concentrations of low molecular mass phenolics (LMMP) was studied in young and mature birch leaves ( Betula pubescens Ehrh.) in trees growing at different distances from Harjavalta copper-nickel smelter, SW Finland. Concentrations of low molecular mass phenolics were determined by analytical HPLC. Contents of individual phenolics correlated negatively with the distance from the smelter: for the young leaves, Pearson correlation coefficients ranged from −0.04 to −0.96. However, these coefficients and differences in concentrations of individual compounds in young leaves between the most polluted (0 km from the factory) site and the control (10 km from the factory) site were significant only for 1- O -galloyl-β-D-(2- O -acetyl)-glucopymnose, neochlorogenic acid ( trans -5-caffeoylquinic acid), trans -5- p -coumaroylquinic acid and quercetin-3- O -β-D-galactopyranoside. In mature leaves, differences between the control and most polluted area were significant only for two compounds: 1- O -galloyl-β-D-(2- O -acetyl)-glucopyranose and neochlorogenic acid. Accordingly, the air pollution of Harjavalta smelter is a stress factor for birch trees associated with accumulation of low molecular mass phenolics in leaves. We discuss use of phenolics as stress and pollution indicators. air pollution, Betula pubescens, birch, heavy metals, phenolic compounds, pollution indicators.
Juha-pekka Salminen - One of the best experts on this subject based on the ideXlab platform.
-
Effects of three years’ increase in density of the geometrid Epirrita autumnata on the change in metabolome of mountain birch trees (Betula pubescens ssp. czerepanovii)
Chemoecology, 2014Co-Authors: Vladimir Ossipov, Tero Klemola, Kai Ruohomäki, Juha-pekka SalminenAbstract:The principal objective of the study was to characterize effects of increasing density of the autumnal moth, Epirrita autumnata (Lepidoptera, Geometridae), for 3 successive years on the change in metabolome of mountain birch trees ( Betula pubescens ssp . czerepanovii ). During the three study years (2000–2002), the larval density varied from low to very high (outbreak) density. Samples of leaves were collected from the same 12 trees at the same phenological stage of the trees each year. The leaves were collected from undamaged trees in the first year, from trees slightly damaged by larvae in the second year, and from trees heavily damaged by larvae in the third year. Metabolome analysis showed that the increase in density of E. autumnata larvae and degree of damage of birch trees caused multiple biochemical changes in the leaves, including increased concentrations of phenolic compounds (proanthocyanidins and hydrolysable tannins) and reduced concentrations of nutritive metabolites (monosaccharides, amino acids and some organic acids). These changes reduced the quality of leaves as food for larvae and, probably, were associated with induced chemical resistance of the birches to herbivorous insects. Additionally, the concentration of α-tocopherol was significantly higher in both slightly and heavily damaged trees. Mechanisms of changes in the metabolism of phenolic compounds and carbohydrates, and the role of α-tocopherol in their regulation are discussed.
-
defensive effect of surface flavonoid aglycones of Betula pubescens leaves against first instar epirrita autumnata larvae
Journal of Chemical Ecology, 2004Co-Authors: Maria Lahtinen, Lauri Kapari, Kyosti Lempa, Elena Valkama, Erkki Haukioja, Vladimir Ossipov, Jari Sinkkonen, Juha-pekka Salminen, Kalevi PihlajaAbstract:The surface of birch leaves contains glandular trichomes that secrete exudates containing flavonoid aglycones. We investigated the biological activities of white birch (Betula pubescens) leaf surface exudates against larvae of the autumnal moth, Epirrita autumnata, a common insect pest of birch. We found that tree-specific mortality (up to 100%) of first instar larvae correlated strongly with the tree-specific contents of surface flavonoid aglycones (rs=0.905) in emerging leaves. We also found that first instars clearly preferred birch buds from which surface exudates had been removed. In addition, the duration of the first instar was shortened by 29%, and the weights and relative growth rates of first instars improved by 8% and 52%, respectively, as a result of removal of the exudates from their leaf diet. The correlation of tree-specific foliar contents of flavonoid aglycones, especially 5-hydroxy-4',7-dimethoxyflavanone, with changes in larval performance, suggests that flavonoid aglycones are responsible for the changes observed in first instar larval performance. The results show that chemical characteristics of birch leaves are effective against neonate E. autumnata larvae. However, the removal of leaf surface exudates from fully expanded leaves did not affect the leaf acceptance for the voracious fifth instars. This is probably a result of reduction in contents of flavonoid aglycones compared to those of emerging leaves.
-
new sesquiterpenoid type bicyclic compounds from the buds of Betula pubescens ring contracted products of β caryophyllene
European Journal of Organic Chemistry, 2004Co-Authors: Karel D Klika, Juha-pekka Salminen, Betul Demirci, Vladimir V Ovcharenko, Satu Vuorela, Husnu Can K Baser, Kalevi PihlajaAbstract:The essential oils obtained from the buds of Betula pubescens ssp. pubescens and B. pubescens ssp. czerepanovii were analyzed both by GC and GC/MS and, of the 31 compounds identified, 14-acetoxy-β-caryophyllene was determined to be the main component in both oils in addition to 25 other previously known compounds. Three of the compounds were isolated from the oils and further characterized by NMR spectroscopy and mass spectrometry, including a new bicyclic aldehyde (4,8,8-trimethyl-2-methylenebicyclo[5.2.0]nonane-4-carbaldehyde, birkenal), a new tricyclic lactone (1,4,4,8-tetramethyl-10-oxatricyclo[6.2.1.02,5]undecan-9-one, hushinone), and the recently described 6-hydroxycaryophyllene. The isolation of birkenal also enabled identification of its corresponding alcohol {(4,8,8-trimethyl-2-methylenebicyclo[5.2.0]non-4-yl)methanol, birkenol} and the acetate of this alcohol {(4,8,8-trimethyl-2-methylenebicyclo[5.2.0]non-4-yl)methyl acetate, birkenyl acetate}, both of which are also novel compounds and are present in the two essential oils. These new compounds, bearing evident sesquiterpenoid traits, potentially arise biosynthetically as ring-contracted products of β-caryophyllene or a derivative thereof. The fifth novel compound present in the oils was determined to be the acetate of 6-hydroxycaryophyllene. The preferred conformations of the seven- or nine-membered rings in these structures were also determined. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
-
Seasonal variation in the content of hydrolysable tannins in leaves of Betula pubescens.
Phytochemistry, 2001Co-Authors: Juha-pekka Salminen, Erkki Haukioja, Vladimir Ossipov, Kalevi PihlajaAbstract:The contents of 13 hydrolysable tannins in the leaves of white birch (Betula pubescens L.) trees were analysed at twelve stages throughout the growing season. All individual galloylglucoses, from 1-O-galloyl-beta-D-glucopyranose to 1,2,3,4,6-penta-O-galloyl-beta-D-glucopyranose, accumulated in young leaves, while ellagitannins showed significantly variable seasonal trends. The major ellagitannin during the whole growing season was pedunculagin while 2,3-(S)-HHDP-glucopyranose. the end product of the proposed ellagitannin pathway, accumulated in mature leaves. Relationships between the characteristics of seasonal variation in the contents of individual ellagitannins and their chemical structures were used to unravel the biogenesis of ellagitannins in birch leaves. Evidence of degradation of ellagitannins through hydrolysis during leaf growth and development is presented and implications for herbivory are discussed.
-
characterisation of hydrolysable tannins from leaves of Betula pubescens by high performance liquid chromatography mass spectrometry
Journal of Chromatography A, 1999Co-Authors: Juha-pekka Salminen, Erkki Haukioja, Vladimir Ossipov, Jyrki Loponen, Kalevi PihlajaAbstract:Abstract A high-performance liquid chromatography–electrospray ionisation mass spectrometry (HPLC–ESI-MS) method, assisted by diode array detection, for the characterisation of individual hydrolysable tannins in birch leaves was developed. With the method, it was found that birch ( Betula pubescens ) leaves contained an exceptionally complex mixture of hydrolysable tannins; 14 gallotannins and 20 ellagitannins were identified. The developed HPLC–ESI-MS method allows the qualitative and quantitative determination of individual gallotannins and ellagitannins directly from crude birch leaf extract. This is important in studying ecological functions of these phenolic compounds, especially their role in the resistance of birch leaves against insects.