The Experts below are selected from a list of 300 Experts worldwide ranked by ideXlab platform
Jonathan Gershenzon - One of the best experts on this subject based on the ideXlab platform.
-
Gallocatechin biosynthesis via a flavonoid 3 5 hydroxylase is a defense response in norway spruce against infection by the bark beetle associated sap staining fungus endoconidiophora polonica
Phytochemistry, 2018Co-Authors: Almuth Hammerbacher, Bettina Raguschke, Louwrance P. Wright, Jonathan GershenzonAbstract:Abstract One of the best-studied defense responses to fungal infection in Norway spruce (Picea abies) is the biosynthesis of flavan-3-ols, which accumulate as monomers or polymers known as proanthocyanidins. The individual flavan-3-ol units consist of compounds with a 3′,4′-dihydroxylated B ring [2,3-(trans)-(+)-catechin or 2,3-(cis)-(−)-epicatechin] and compounds with a 3′,4′,5′-trihydroxylated B ring [2,3 (trans)-(+)-Gallocatechin or 2,3-(cis)-(−)-epiGallocatechin]. While much is known about the biosynthesis and biological activity of catechin in Norway spruce, there is little comparable information about Gallocatechin or epiGallocatechin. We found that there was a significant increase in the Gallocatechin content of Norway spruce bark and wood after inoculation with the bark beetle-associated sap-staining fungus Endoconidiophora polonica. Gallocatechins increased proportionally more than catechins as both monomers and units of polymers. A flavonoid 3′,5′-hydroxylase gene identified in Norway spruce was shown by heterologous expression in Nicotiana benthamiana to be involved in the conversion of 2,3 (trans)-(+)-catechin to 2,3 (trans)-(+)-Gallocatechin. The formation of the trihydroxylated B ring in Norway spruce occurs at the level of flavan-3-ols, rather than at the level of dihydroflavonols as in many angiosperms. The transcript abundance of the flavonoid 3′,5′-hydroxylase gene also increased significantly during fungal infection underlining its importance in Gallocatechin biosynthesis. Comparisons of the effect of 2,3 (trans)-(+)-catechin and 2,3 (trans)-(+)-Gallocatechin on fungal growth revealed that 2,3 (trans)-(+)-catechin is a stronger inhibitor of fungal growth, while 2,3 (trans)-(+)-Gallocatechin is a stronger inhibitor of melanin biosynthesis.
-
Gallocatechin biosynthesis via a flavonoid 3′,5′-hydroxylase is a defense response in Norway spruce against infection by the bark beetle-associated sap-staining fungus Endoconidiophora polonica
Phytochemistry, 2018Co-Authors: Almuth Hammerbacher, Bettina Raguschke, Louwrance P. Wright, Jonathan GershenzonAbstract:Abstract One of the best-studied defense responses to fungal infection in Norway spruce (Picea abies) is the biosynthesis of flavan-3-ols, which accumulate as monomers or polymers known as proanthocyanidins. The individual flavan-3-ol units consist of compounds with a 3′,4′-dihydroxylated B ring [2,3-(trans)-(+)-catechin or 2,3-(cis)-(−)-epicatechin] and compounds with a 3′,4′,5′-trihydroxylated B ring [2,3 (trans)-(+)-Gallocatechin or 2,3-(cis)-(−)-epiGallocatechin]. While much is known about the biosynthesis and biological activity of catechin in Norway spruce, there is little comparable information about Gallocatechin or epiGallocatechin. We found that there was a significant increase in the Gallocatechin content of Norway spruce bark and wood after inoculation with the bark beetle-associated sap-staining fungus Endoconidiophora polonica. Gallocatechins increased proportionally more than catechins as both monomers and units of polymers. A flavonoid 3′,5′-hydroxylase gene identified in Norway spruce was shown by heterologous expression in Nicotiana benthamiana to be involved in the conversion of 2,3 (trans)-(+)-catechin to 2,3 (trans)-(+)-Gallocatechin. The formation of the trihydroxylated B ring in Norway spruce occurs at the level of flavan-3-ols, rather than at the level of dihydroflavonols as in many angiosperms. The transcript abundance of the flavonoid 3′,5′-hydroxylase gene also increased significantly during fungal infection underlining its importance in Gallocatechin biosynthesis. Comparisons of the effect of 2,3 (trans)-(+)-catechin and 2,3 (trans)-(+)-Gallocatechin on fungal growth revealed that 2,3 (trans)-(+)-catechin is a stronger inhibitor of fungal growth, while 2,3 (trans)-(+)-Gallocatechin is a stronger inhibitor of melanin biosynthesis.
Sonia Collin - One of the best experts on this subject based on the ideXlab platform.
-
use of thiolysis hyphenated to rp hplc esi ms ms for the analysis of flavanoids in fresh lager beers
Food Chemistry, 2008Co-Authors: Delphine Callemien, Sylvain Guyot, Sonia CollinAbstract:Proanthocyanidins are well known for their involvement in haze and colour development during beer ageing. New methodologies are needed, however, to understand what happens to them in the bottled beer. For the first time in the brewing Held, thiolysis was hyphenated to RP-HPLC-ESI(-)-MS/MS to investigate these flavanoids. Thirty minutes at 40 degrees C followed by 10 h at room temperature emerged as the best conditions for complete depolymerisation. NP-HPLC-ESI(-)-MS/MS was used to quantify and isolate fractions from monomers to trimers in a Sephadex LH20 acetone/water (70/30, v/v) beer extract. Unsurprisingly, a lower dimer/monomer ratio was evidenced in PVPP-treated beers than in silica gel-filtered beers. Most beer dimers are procyanidins B3 (two catechin units) whilst most trimers are prodelphinidins (catechin in terminal units and Gallocatechins or catechins in extension units). Gallocatechin appeared to come mainly from malt. Despite the absence of chromatographic peaks corresponding to oligomers above trimers, an apparent degree of polymerisation close to six was calculated in the total LH20 extract. Still higher mean degrees of polymerisation (mDPs) were calculated for malt and hop, indicating selective extraction or depolymerisation from raw materials to beer. The main part of beer polyphenols is composed of complex undefined structures not degraded by toluene-alpha-thiol. (C) 2008 Elsevier Ltd. All rights reserved.
-
Use of thiolysis hyphenated to RP-HPLC-ESI(-)-MS/MS for the analysis of flavanoids in fresh lager beers
Food chemistry, 2008Co-Authors: Delphine Callemien, Sylvain Guyot, Sonia CollinAbstract:Proanthocyanidins are well known for their involvement in haze and colour development during beer ageing. New methodologies are needed, however, to understand what happens to them in the bottled beer. For the first time in the brewing field, thiolysis was hyphenated to RP-HPLC-ESI(-)-MS/MS to investigate these flavanoids. Thirty minutes at 40°C followed by 10h at room temperature emerged as the best conditions for complete depolymerisation. NP-HPLC-ESI(-)-MS/MS was used to quantify and isolate fractions from monomers to trimers in a Sephadex LH20 acetone/water (70/30, v/v) beer extract. Unsurprisingly, a lower dimer/monomer ratio was evidenced in PVPP-treated beers than in silica gel-filtered beers. Most beer dimers are procyanidins B3 (two catechin units) whilst most trimers are prodelphinidins (catechin in terminal units and Gallocatechins or catechins in extension units). Gallocatechin appeared to come mainly from malt. Despite the absence of chromatographic peaks corresponding to oligomers above trimers, an apparent degree of polymerisation close to six was calculated in the total LH20 extract. Still higher mean degrees of polymerisation (mDPs) were calculated for malt and hop, indicating selective extraction or depolymerisation from raw materials to beer. The main part of beer polyphenols is composed of complex undefined structures not degraded by toluene-α-thiol.
Almuth Hammerbacher - One of the best experts on this subject based on the ideXlab platform.
-
Gallocatechin biosynthesis via a flavonoid 3 5 hydroxylase is a defense response in norway spruce against infection by the bark beetle associated sap staining fungus endoconidiophora polonica
Phytochemistry, 2018Co-Authors: Almuth Hammerbacher, Bettina Raguschke, Louwrance P. Wright, Jonathan GershenzonAbstract:Abstract One of the best-studied defense responses to fungal infection in Norway spruce (Picea abies) is the biosynthesis of flavan-3-ols, which accumulate as monomers or polymers known as proanthocyanidins. The individual flavan-3-ol units consist of compounds with a 3′,4′-dihydroxylated B ring [2,3-(trans)-(+)-catechin or 2,3-(cis)-(−)-epicatechin] and compounds with a 3′,4′,5′-trihydroxylated B ring [2,3 (trans)-(+)-Gallocatechin or 2,3-(cis)-(−)-epiGallocatechin]. While much is known about the biosynthesis and biological activity of catechin in Norway spruce, there is little comparable information about Gallocatechin or epiGallocatechin. We found that there was a significant increase in the Gallocatechin content of Norway spruce bark and wood after inoculation with the bark beetle-associated sap-staining fungus Endoconidiophora polonica. Gallocatechins increased proportionally more than catechins as both monomers and units of polymers. A flavonoid 3′,5′-hydroxylase gene identified in Norway spruce was shown by heterologous expression in Nicotiana benthamiana to be involved in the conversion of 2,3 (trans)-(+)-catechin to 2,3 (trans)-(+)-Gallocatechin. The formation of the trihydroxylated B ring in Norway spruce occurs at the level of flavan-3-ols, rather than at the level of dihydroflavonols as in many angiosperms. The transcript abundance of the flavonoid 3′,5′-hydroxylase gene also increased significantly during fungal infection underlining its importance in Gallocatechin biosynthesis. Comparisons of the effect of 2,3 (trans)-(+)-catechin and 2,3 (trans)-(+)-Gallocatechin on fungal growth revealed that 2,3 (trans)-(+)-catechin is a stronger inhibitor of fungal growth, while 2,3 (trans)-(+)-Gallocatechin is a stronger inhibitor of melanin biosynthesis.
-
Gallocatechin biosynthesis via a flavonoid 3′,5′-hydroxylase is a defense response in Norway spruce against infection by the bark beetle-associated sap-staining fungus Endoconidiophora polonica
Phytochemistry, 2018Co-Authors: Almuth Hammerbacher, Bettina Raguschke, Louwrance P. Wright, Jonathan GershenzonAbstract:Abstract One of the best-studied defense responses to fungal infection in Norway spruce (Picea abies) is the biosynthesis of flavan-3-ols, which accumulate as monomers or polymers known as proanthocyanidins. The individual flavan-3-ol units consist of compounds with a 3′,4′-dihydroxylated B ring [2,3-(trans)-(+)-catechin or 2,3-(cis)-(−)-epicatechin] and compounds with a 3′,4′,5′-trihydroxylated B ring [2,3 (trans)-(+)-Gallocatechin or 2,3-(cis)-(−)-epiGallocatechin]. While much is known about the biosynthesis and biological activity of catechin in Norway spruce, there is little comparable information about Gallocatechin or epiGallocatechin. We found that there was a significant increase in the Gallocatechin content of Norway spruce bark and wood after inoculation with the bark beetle-associated sap-staining fungus Endoconidiophora polonica. Gallocatechins increased proportionally more than catechins as both monomers and units of polymers. A flavonoid 3′,5′-hydroxylase gene identified in Norway spruce was shown by heterologous expression in Nicotiana benthamiana to be involved in the conversion of 2,3 (trans)-(+)-catechin to 2,3 (trans)-(+)-Gallocatechin. The formation of the trihydroxylated B ring in Norway spruce occurs at the level of flavan-3-ols, rather than at the level of dihydroflavonols as in many angiosperms. The transcript abundance of the flavonoid 3′,5′-hydroxylase gene also increased significantly during fungal infection underlining its importance in Gallocatechin biosynthesis. Comparisons of the effect of 2,3 (trans)-(+)-catechin and 2,3 (trans)-(+)-Gallocatechin on fungal growth revealed that 2,3 (trans)-(+)-catechin is a stronger inhibitor of fungal growth, while 2,3 (trans)-(+)-Gallocatechin is a stronger inhibitor of melanin biosynthesis.
Delphine Callemien - One of the best experts on this subject based on the ideXlab platform.
-
use of thiolysis hyphenated to rp hplc esi ms ms for the analysis of flavanoids in fresh lager beers
Food Chemistry, 2008Co-Authors: Delphine Callemien, Sylvain Guyot, Sonia CollinAbstract:Proanthocyanidins are well known for their involvement in haze and colour development during beer ageing. New methodologies are needed, however, to understand what happens to them in the bottled beer. For the first time in the brewing Held, thiolysis was hyphenated to RP-HPLC-ESI(-)-MS/MS to investigate these flavanoids. Thirty minutes at 40 degrees C followed by 10 h at room temperature emerged as the best conditions for complete depolymerisation. NP-HPLC-ESI(-)-MS/MS was used to quantify and isolate fractions from monomers to trimers in a Sephadex LH20 acetone/water (70/30, v/v) beer extract. Unsurprisingly, a lower dimer/monomer ratio was evidenced in PVPP-treated beers than in silica gel-filtered beers. Most beer dimers are procyanidins B3 (two catechin units) whilst most trimers are prodelphinidins (catechin in terminal units and Gallocatechins or catechins in extension units). Gallocatechin appeared to come mainly from malt. Despite the absence of chromatographic peaks corresponding to oligomers above trimers, an apparent degree of polymerisation close to six was calculated in the total LH20 extract. Still higher mean degrees of polymerisation (mDPs) were calculated for malt and hop, indicating selective extraction or depolymerisation from raw materials to beer. The main part of beer polyphenols is composed of complex undefined structures not degraded by toluene-alpha-thiol. (C) 2008 Elsevier Ltd. All rights reserved.
-
Use of thiolysis hyphenated to RP-HPLC-ESI(-)-MS/MS for the analysis of flavanoids in fresh lager beers
Food chemistry, 2008Co-Authors: Delphine Callemien, Sylvain Guyot, Sonia CollinAbstract:Proanthocyanidins are well known for their involvement in haze and colour development during beer ageing. New methodologies are needed, however, to understand what happens to them in the bottled beer. For the first time in the brewing field, thiolysis was hyphenated to RP-HPLC-ESI(-)-MS/MS to investigate these flavanoids. Thirty minutes at 40°C followed by 10h at room temperature emerged as the best conditions for complete depolymerisation. NP-HPLC-ESI(-)-MS/MS was used to quantify and isolate fractions from monomers to trimers in a Sephadex LH20 acetone/water (70/30, v/v) beer extract. Unsurprisingly, a lower dimer/monomer ratio was evidenced in PVPP-treated beers than in silica gel-filtered beers. Most beer dimers are procyanidins B3 (two catechin units) whilst most trimers are prodelphinidins (catechin in terminal units and Gallocatechins or catechins in extension units). Gallocatechin appeared to come mainly from malt. Despite the absence of chromatographic peaks corresponding to oligomers above trimers, an apparent degree of polymerisation close to six was calculated in the total LH20 extract. Still higher mean degrees of polymerisation (mDPs) were calculated for malt and hop, indicating selective extraction or depolymerisation from raw materials to beer. The main part of beer polyphenols is composed of complex undefined structures not degraded by toluene-α-thiol.
Takami Kakuda - One of the best experts on this subject based on the ideXlab platform.
-
Heat-epimerized tea catechins rich in Gallocatechin gallate and catechin gallate are more effective to inhibit cholesterol absorption than tea catechins rich in epiGallocatechin gallate and epicatechin gallate.
Journal of Agricultural and Food Chemistry, 2003Co-Authors: Ikuo Ikeda, Tadateru Hamada, Koichi Tsuda, Hitomi Goto, Ayumu Nozawa, And Akio Sugimoto, Katsumi Imaizumi, Makoto Kobayashi, Takami KakudaAbstract:It has been known that tea catechins, (−)-epicatechin (1), (−)-epiGallocatechin (2), (−)-epicatechin gallate (3), and (−)-epiGallocatechin gallate (4) are epimerized to(−)-catechin (5), (−)-Gallocatechin (6), (−)-catechin gallate (7), and (−)-Gallocatechin gallate (8), respectively, during retort pasteurization. We previously reported that tea catechins, mainly composed of 3 and 4, effectively inhibit cholesterol absorption in rats. In this study, the effect of heat-epimerized catechins on cholesterol absorption was compared with tea catechins. Both tea catechins and heat-epimerized catechins lowered lymphatic recovery of cholesterol in rats cannulated in the thoracic duct and epimerized catechins were more effective than tea catechins. The effect of purified catechins on micellar solubility of cholesterol was examined in an in vitro study. The addition of gallate esters of catechins reduced micellar solubility of cholesterol by precipitating cholesterol from bile salt micelles. Compounds 7 and 8 were mor...
-
Heat-epimerized tea catechins rich in Gallocatechin gallate and catechin gallate are more effective to inhibit cholesterol absorption than tea catechins rich in epiGallocatechin gallate and epicatechin gallate.
Journal of agricultural and food chemistry, 2003Co-Authors: Ikuo Ikeda, Tadateru Hamada, Koichi Tsuda, Hitomi Goto, Ayumu Nozawa, And Akio Sugimoto, Katsumi Imaizumi, Makoto Kobayashi, Takami KakudaAbstract:It has been known that tea catechins, (-)-epicatechin (1), (-)-epiGallocatechin (2), (-)-epicatechin gallate (3), and (-)-epiGallocatechin gallate (4) are epimerized to(-)-catechin (5), (-)-Gallocatechin (6), (-)-catechin gallate (7), and (-)-Gallocatechin gallate (8), respectively, during retort pasteurization. We previously reported that tea catechins, mainly composed of 3 and 4, effectively inhibit cholesterol absorption in rats. In this study, the effect of heat-epimerized catechins on cholesterol absorption was compared with tea catechins. Both tea catechins and heat-epimerized catechins lowered lymphatic recovery of cholesterol in rats cannulated in the thoracic duct and epimerized catechins were more effective than tea catechins. The effect of purified catechins on micellar solubility of cholesterol was examined in an in vitro study. The addition of gallate esters of catechins reduced micellar solubility of cholesterol by precipitating cholesterol from bile salt micelles. Compounds 7 and 8 were more effective to precipitate cholesterol than 3 and 4, respectively. These observations strongly suggest that heat-epimerized catechins may be more hypocholesterolemic than tea catechins.
