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Maria Eugênia R. Duarte - One of the best experts on this subject based on the ideXlab platform.
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structure and anti metapneumovirus activity of sulfated galactans from the red seaweed Cryptonemia seminervis
Carbohydrate Polymers, 2014Co-Authors: Gabriella Da Silva Mendes, Miguel D. Noseda, Maria Eugênia R. Duarte, Franciely G Colodi, Luciana G Ferreira, Siliane D Berte, Jessica F Cavalcanti, Norma Santos, Maria Teresa Villela RomanosAbstract:Abstract The anti-HMPV (human metapneumovirus) activity was determined for sulfated dl -hybrid galactans obtained from the red seaweed Cryptonemia seminervis and their depolymerized products obtained by reductive partial hydrolysis. Structural studies carried out in three homogeneous depolymerized fractions DS-1, DS-2e and DS-3 (Mw of 51.6–63.8 kDa) showed that these galactans present different chemical characteristics, as monosaccharide composition, content of sulfate groups (14.1–29.9%) and agaran:carrageenan molar ratio diads, 2.7:1 for DS-1 and DS-2e and 1:1 for DS-3. The sulfate groups are located principally on C-2 of β- d -galactopyranose and 4,6-O-(1′-carboxyethylidene)-β- d -galactopyranose residues and on C-6 of α-galactose residues. Sulfated dl -galactans and their depolymerized products exhibited antiviral activity at a very early stage of the viral infection cycle. All fractions, except DS-2e inhibited HMPV replication by binding to the viral particle. Besides depolymerized galactans DS-2e and DS-3 inhibited the recognition of cell receptor by HMPV and penetration to the host cell, respectively.
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galactans from Cryptonemia species part ii studies on the system of galactans of Cryptonemia seminervis halymeniales and on the structure of major fractions
Carbohydrate Research, 2009Co-Authors: Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Franciely G Colodi, Diogo R B Ducatti, Luciana G Ferreira, Marco Andre Cardoso, Alberto S. CerezoAbstract:Abstract Cryptonemia seminervis biosynthesizes a family of d , l -hybrid galactans based on the classical 3-linked β- d -galactopyranosyl→4-linked α- d - and α- l -galactopyranosyl alternating sequence (A-units→B-units) with major amounts of α- d - and α- l -galactose and 3,6-anhydro- d - and l -galactose and lesser percentages of 3,6-anhydro-2-O-methyl- l -galactose, 2-O-methyl-, 4-O-methyl- and 6-O-methylgalactoses. The dispersion of structures in this family is based on five structural factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and glycosyl side-chain (4-O-methyl galactopyranosyl and/or xylosyl); (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio d , l -galactoses and d , l -3,6-anhydrogalactoses also in the B-units, (d) the formation of diads and (e) the sequence of the diads in the linear backbone. Considering these variables it is not unexpected to find in the fractions studied at least 18 structural units producing highly complex structures. Structural studies carried out in two major fractions (S2S-3 and S2S-4) showed that these galactans were formed mainly by β- d -galactopyranosyl 2-sulfate (20 and 11.9 mol %), β- d -galactopyranosyl 2-sulfate 4,6-O-(1′-carboxyethylidene) (8.9 and 6.0 mol %) and β- d -galactopyranosyl 2,6-sulfate (5.4 and 18.6 mol %), together with 3,6-anhydro-α- l -galactopyranosyl (11.4 and 7.3 mol %) and 3,6-anhydro-α- l -galactopyranosyl 2-sulfate (4.9 and 15.4 mol %) and minor quantities of 12–15 other structural units. Preparative alkaline treatment carried out on fraction (S2S-3) produced a quantitative formation of 3,6-anhydro α- l -galactopyranosyl units from precursor units (α- l -galactose 6-sulfate and α- l -galactose 2,6-sulfate). Kinetic studies on this 3,6-anhydro cyclization show a rate constant of 5.2 × 104 s−1 indicating diads of the type G→L6S/2,6S. Data from chemical, spectroscopic and kinetic studies suggest that, in S2S-3, the agaran block in the d , l -hybrid galactan is composed of the following diads: G(6R)→L6S/2,6S and G2S(P)(2,6S)→LA(2S)(2R)(2M) and the carrageenan block of G2S(P)→D(2S)(2,3S)(3S)(3,6S) in a molar ratio of agaran to carrageenan structures of ∼2:1.
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an algal derived dl galactan hybrid is an efficient preventing agent for in vitro dengue virus infection
Planta Medica, 2007Co-Authors: Laura B Talarico, Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Elsa B DamonteAbstract:The DL-galactan hybrid C2S-3, isolated from the red seaweed Cryptonemia crenulata (Halymeniaceae, Halymeniales), is a potent and selective inhibitor of the multiplication of diverse strains of DENV-2 in Vero cells with higher effectiveness than the reference polysaccharide heparin. The presence of the compound either only at virus adsorption or at virus internalization exerted a significant and dose-dependent inhibition in DENV-2 plaque number. The compound failed to inactivate DENV-2 directly by incubation of virus before cell infection as well as to induce a refractory state by cell pretreatment. Thus, the inhibitory effect was exclusively exerted through a blockade in virus multiplication during the infectious process. When the entry of DENV-2 particles into the cell is bypassed, as occurs in virus RNA transfection, the polysaccharide C2S-3 failed to block the completion of the multiplication cycle. Furthermore, the antiviral properties of C2S-3 are not correlated with anticoagulant activity.
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The system of galactans from Cryptonemia crenulata (Halymeniaceae, Halymeniales) and the structure of two major fractions. Kinetic studies on the alkaline cyclization of the unusual diad G2S-->D(L)6S.
Carbohydrate research, 2005Co-Authors: Rosiane G.m. Zibetti, Miguel D. Noseda, Alberto S. Cerezo, Maria Eugênia R. DuarteAbstract:Cryptonemia crenulata biosynthesizes a family of dl-hybrid galactans that are based on the classical 3-linked beta-d-galactopyranosyl-->4-linked alpha-galactopyranosyl alternating sequence (A-units-->B-units). The dispersion of structures in these galactans is based on four factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and side substituents of beta-D-xylose and/or beta-D-galactose; (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio D-/L-galactoses and 3,6-anhydrogalactoses also in the B-units and (d) the sequence of the diads in the linear backbone. Alkali treatment carried out on the major fraction produced a nearly quantitative formation of 3,6-anhydrogalactose units from precursor units (alpha-galactose 6-sulfate (major) and alpha-galactose 2,6-sulfate, minor). Kinetic studies show a rate constant, for the diad G2S-D(L) 6-S, of 1.7 x 10(4)s(-1) indicating a reaction faster than in lambda-carrageenans but slower than in porphyrans.
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anti herpes simplex virus activity of sulfated galactans from the red seaweeds gymnogongrus griffithsiae and Cryptonemia crenulata
International Journal of Biological Macromolecules, 2004Co-Authors: Laura B Talarico, Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Paula C S Faria, Luis A Scolaro, Carlos A Pujol, Elsa B DamonteAbstract:This study presents the chemical composition and antiviral activity against herpes simplex virus type 1 (HSV-1) and 2 (HSV-2) of sulfated galactan crude extracts and main fractions obtained from two red seaweeds collected in Brazil, Gymnogongrus griffithsiae and Cryptonemia crenulata. Most of the eighteen tested products, including homogeneous kappa/iota/nu carrageenan and DL-galactan hybrid, exhibited antiherpetic activity with inhibitory concentration 50% (IC50) values in the range 0.5-5.6 microg/ml, as determined in a virus plaque reduction assay in Vero cells. The galactans lacked cytotoxic effects and showed a broad spectrum of antiviral activity against HSV-1 and HSV-2. No direct virus inactivation was observed after virion treatment with the galactans. The mode of action of these compounds could be mainly ascribed to an inhibitory effect on virus adsorption. Most importantly, a significant protection against a murine vaginal infection with HSV-2 was afforded by topical treatment with the sulfated galactans.
Rosiane G.m. Zibetti - One of the best experts on this subject based on the ideXlab platform.
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galactans from Cryptonemia species part ii studies on the system of galactans of Cryptonemia seminervis halymeniales and on the structure of major fractions
Carbohydrate Research, 2009Co-Authors: Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Franciely G Colodi, Diogo R B Ducatti, Luciana G Ferreira, Marco Andre Cardoso, Alberto S. CerezoAbstract:Abstract Cryptonemia seminervis biosynthesizes a family of d , l -hybrid galactans based on the classical 3-linked β- d -galactopyranosyl→4-linked α- d - and α- l -galactopyranosyl alternating sequence (A-units→B-units) with major amounts of α- d - and α- l -galactose and 3,6-anhydro- d - and l -galactose and lesser percentages of 3,6-anhydro-2-O-methyl- l -galactose, 2-O-methyl-, 4-O-methyl- and 6-O-methylgalactoses. The dispersion of structures in this family is based on five structural factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and glycosyl side-chain (4-O-methyl galactopyranosyl and/or xylosyl); (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio d , l -galactoses and d , l -3,6-anhydrogalactoses also in the B-units, (d) the formation of diads and (e) the sequence of the diads in the linear backbone. Considering these variables it is not unexpected to find in the fractions studied at least 18 structural units producing highly complex structures. Structural studies carried out in two major fractions (S2S-3 and S2S-4) showed that these galactans were formed mainly by β- d -galactopyranosyl 2-sulfate (20 and 11.9 mol %), β- d -galactopyranosyl 2-sulfate 4,6-O-(1′-carboxyethylidene) (8.9 and 6.0 mol %) and β- d -galactopyranosyl 2,6-sulfate (5.4 and 18.6 mol %), together with 3,6-anhydro-α- l -galactopyranosyl (11.4 and 7.3 mol %) and 3,6-anhydro-α- l -galactopyranosyl 2-sulfate (4.9 and 15.4 mol %) and minor quantities of 12–15 other structural units. Preparative alkaline treatment carried out on fraction (S2S-3) produced a quantitative formation of 3,6-anhydro α- l -galactopyranosyl units from precursor units (α- l -galactose 6-sulfate and α- l -galactose 2,6-sulfate). Kinetic studies on this 3,6-anhydro cyclization show a rate constant of 5.2 × 104 s−1 indicating diads of the type G→L6S/2,6S. Data from chemical, spectroscopic and kinetic studies suggest that, in S2S-3, the agaran block in the d , l -hybrid galactan is composed of the following diads: G(6R)→L6S/2,6S and G2S(P)(2,6S)→LA(2S)(2R)(2M) and the carrageenan block of G2S(P)→D(2S)(2,3S)(3S)(3,6S) in a molar ratio of agaran to carrageenan structures of ∼2:1.
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an algal derived dl galactan hybrid is an efficient preventing agent for in vitro dengue virus infection
Planta Medica, 2007Co-Authors: Laura B Talarico, Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Elsa B DamonteAbstract:The DL-galactan hybrid C2S-3, isolated from the red seaweed Cryptonemia crenulata (Halymeniaceae, Halymeniales), is a potent and selective inhibitor of the multiplication of diverse strains of DENV-2 in Vero cells with higher effectiveness than the reference polysaccharide heparin. The presence of the compound either only at virus adsorption or at virus internalization exerted a significant and dose-dependent inhibition in DENV-2 plaque number. The compound failed to inactivate DENV-2 directly by incubation of virus before cell infection as well as to induce a refractory state by cell pretreatment. Thus, the inhibitory effect was exclusively exerted through a blockade in virus multiplication during the infectious process. When the entry of DENV-2 particles into the cell is bypassed, as occurs in virus RNA transfection, the polysaccharide C2S-3 failed to block the completion of the multiplication cycle. Furthermore, the antiviral properties of C2S-3 are not correlated with anticoagulant activity.
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The system of galactans from Cryptonemia crenulata (Halymeniaceae, Halymeniales) and the structure of two major fractions. Kinetic studies on the alkaline cyclization of the unusual diad G2S-->D(L)6S.
Carbohydrate research, 2005Co-Authors: Rosiane G.m. Zibetti, Miguel D. Noseda, Alberto S. Cerezo, Maria Eugênia R. DuarteAbstract:Cryptonemia crenulata biosynthesizes a family of dl-hybrid galactans that are based on the classical 3-linked beta-d-galactopyranosyl-->4-linked alpha-galactopyranosyl alternating sequence (A-units-->B-units). The dispersion of structures in these galactans is based on four factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and side substituents of beta-D-xylose and/or beta-D-galactose; (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio D-/L-galactoses and 3,6-anhydrogalactoses also in the B-units and (d) the sequence of the diads in the linear backbone. Alkali treatment carried out on the major fraction produced a nearly quantitative formation of 3,6-anhydrogalactose units from precursor units (alpha-galactose 6-sulfate (major) and alpha-galactose 2,6-sulfate, minor). Kinetic studies show a rate constant, for the diad G2S-D(L) 6-S, of 1.7 x 10(4)s(-1) indicating a reaction faster than in lambda-carrageenans but slower than in porphyrans.
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anti herpes simplex virus activity of sulfated galactans from the red seaweeds gymnogongrus griffithsiae and Cryptonemia crenulata
International Journal of Biological Macromolecules, 2004Co-Authors: Laura B Talarico, Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Paula C S Faria, Luis A Scolaro, Carlos A Pujol, Elsa B DamonteAbstract:This study presents the chemical composition and antiviral activity against herpes simplex virus type 1 (HSV-1) and 2 (HSV-2) of sulfated galactan crude extracts and main fractions obtained from two red seaweeds collected in Brazil, Gymnogongrus griffithsiae and Cryptonemia crenulata. Most of the eighteen tested products, including homogeneous kappa/iota/nu carrageenan and DL-galactan hybrid, exhibited antiherpetic activity with inhibitory concentration 50% (IC50) values in the range 0.5-5.6 microg/ml, as determined in a virus plaque reduction assay in Vero cells. The galactans lacked cytotoxic effects and showed a broad spectrum of antiviral activity against HSV-1 and HSV-2. No direct virus inactivation was observed after virion treatment with the galactans. The mode of action of these compounds could be mainly ascribed to an inhibitory effect on virus adsorption. Most importantly, a significant protection against a murine vaginal infection with HSV-2 was afforded by topical treatment with the sulfated galactans.
Miguel D. Noseda - One of the best experts on this subject based on the ideXlab platform.
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structure and anti metapneumovirus activity of sulfated galactans from the red seaweed Cryptonemia seminervis
Carbohydrate Polymers, 2014Co-Authors: Gabriella Da Silva Mendes, Miguel D. Noseda, Maria Eugênia R. Duarte, Franciely G Colodi, Luciana G Ferreira, Siliane D Berte, Jessica F Cavalcanti, Norma Santos, Maria Teresa Villela RomanosAbstract:Abstract The anti-HMPV (human metapneumovirus) activity was determined for sulfated dl -hybrid galactans obtained from the red seaweed Cryptonemia seminervis and their depolymerized products obtained by reductive partial hydrolysis. Structural studies carried out in three homogeneous depolymerized fractions DS-1, DS-2e and DS-3 (Mw of 51.6–63.8 kDa) showed that these galactans present different chemical characteristics, as monosaccharide composition, content of sulfate groups (14.1–29.9%) and agaran:carrageenan molar ratio diads, 2.7:1 for DS-1 and DS-2e and 1:1 for DS-3. The sulfate groups are located principally on C-2 of β- d -galactopyranose and 4,6-O-(1′-carboxyethylidene)-β- d -galactopyranose residues and on C-6 of α-galactose residues. Sulfated dl -galactans and their depolymerized products exhibited antiviral activity at a very early stage of the viral infection cycle. All fractions, except DS-2e inhibited HMPV replication by binding to the viral particle. Besides depolymerized galactans DS-2e and DS-3 inhibited the recognition of cell receptor by HMPV and penetration to the host cell, respectively.
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galactans from Cryptonemia species part ii studies on the system of galactans of Cryptonemia seminervis halymeniales and on the structure of major fractions
Carbohydrate Research, 2009Co-Authors: Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Franciely G Colodi, Diogo R B Ducatti, Luciana G Ferreira, Marco Andre Cardoso, Alberto S. CerezoAbstract:Abstract Cryptonemia seminervis biosynthesizes a family of d , l -hybrid galactans based on the classical 3-linked β- d -galactopyranosyl→4-linked α- d - and α- l -galactopyranosyl alternating sequence (A-units→B-units) with major amounts of α- d - and α- l -galactose and 3,6-anhydro- d - and l -galactose and lesser percentages of 3,6-anhydro-2-O-methyl- l -galactose, 2-O-methyl-, 4-O-methyl- and 6-O-methylgalactoses. The dispersion of structures in this family is based on five structural factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and glycosyl side-chain (4-O-methyl galactopyranosyl and/or xylosyl); (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio d , l -galactoses and d , l -3,6-anhydrogalactoses also in the B-units, (d) the formation of diads and (e) the sequence of the diads in the linear backbone. Considering these variables it is not unexpected to find in the fractions studied at least 18 structural units producing highly complex structures. Structural studies carried out in two major fractions (S2S-3 and S2S-4) showed that these galactans were formed mainly by β- d -galactopyranosyl 2-sulfate (20 and 11.9 mol %), β- d -galactopyranosyl 2-sulfate 4,6-O-(1′-carboxyethylidene) (8.9 and 6.0 mol %) and β- d -galactopyranosyl 2,6-sulfate (5.4 and 18.6 mol %), together with 3,6-anhydro-α- l -galactopyranosyl (11.4 and 7.3 mol %) and 3,6-anhydro-α- l -galactopyranosyl 2-sulfate (4.9 and 15.4 mol %) and minor quantities of 12–15 other structural units. Preparative alkaline treatment carried out on fraction (S2S-3) produced a quantitative formation of 3,6-anhydro α- l -galactopyranosyl units from precursor units (α- l -galactose 6-sulfate and α- l -galactose 2,6-sulfate). Kinetic studies on this 3,6-anhydro cyclization show a rate constant of 5.2 × 104 s−1 indicating diads of the type G→L6S/2,6S. Data from chemical, spectroscopic and kinetic studies suggest that, in S2S-3, the agaran block in the d , l -hybrid galactan is composed of the following diads: G(6R)→L6S/2,6S and G2S(P)(2,6S)→LA(2S)(2R)(2M) and the carrageenan block of G2S(P)→D(2S)(2,3S)(3S)(3,6S) in a molar ratio of agaran to carrageenan structures of ∼2:1.
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an algal derived dl galactan hybrid is an efficient preventing agent for in vitro dengue virus infection
Planta Medica, 2007Co-Authors: Laura B Talarico, Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Elsa B DamonteAbstract:The DL-galactan hybrid C2S-3, isolated from the red seaweed Cryptonemia crenulata (Halymeniaceae, Halymeniales), is a potent and selective inhibitor of the multiplication of diverse strains of DENV-2 in Vero cells with higher effectiveness than the reference polysaccharide heparin. The presence of the compound either only at virus adsorption or at virus internalization exerted a significant and dose-dependent inhibition in DENV-2 plaque number. The compound failed to inactivate DENV-2 directly by incubation of virus before cell infection as well as to induce a refractory state by cell pretreatment. Thus, the inhibitory effect was exclusively exerted through a blockade in virus multiplication during the infectious process. When the entry of DENV-2 particles into the cell is bypassed, as occurs in virus RNA transfection, the polysaccharide C2S-3 failed to block the completion of the multiplication cycle. Furthermore, the antiviral properties of C2S-3 are not correlated with anticoagulant activity.
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The system of galactans from Cryptonemia crenulata (Halymeniaceae, Halymeniales) and the structure of two major fractions. Kinetic studies on the alkaline cyclization of the unusual diad G2S-->D(L)6S.
Carbohydrate research, 2005Co-Authors: Rosiane G.m. Zibetti, Miguel D. Noseda, Alberto S. Cerezo, Maria Eugênia R. DuarteAbstract:Cryptonemia crenulata biosynthesizes a family of dl-hybrid galactans that are based on the classical 3-linked beta-d-galactopyranosyl-->4-linked alpha-galactopyranosyl alternating sequence (A-units-->B-units). The dispersion of structures in these galactans is based on four factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and side substituents of beta-D-xylose and/or beta-D-galactose; (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio D-/L-galactoses and 3,6-anhydrogalactoses also in the B-units and (d) the sequence of the diads in the linear backbone. Alkali treatment carried out on the major fraction produced a nearly quantitative formation of 3,6-anhydrogalactose units from precursor units (alpha-galactose 6-sulfate (major) and alpha-galactose 2,6-sulfate, minor). Kinetic studies show a rate constant, for the diad G2S-D(L) 6-S, of 1.7 x 10(4)s(-1) indicating a reaction faster than in lambda-carrageenans but slower than in porphyrans.
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anti herpes simplex virus activity of sulfated galactans from the red seaweeds gymnogongrus griffithsiae and Cryptonemia crenulata
International Journal of Biological Macromolecules, 2004Co-Authors: Laura B Talarico, Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Paula C S Faria, Luis A Scolaro, Carlos A Pujol, Elsa B DamonteAbstract:This study presents the chemical composition and antiviral activity against herpes simplex virus type 1 (HSV-1) and 2 (HSV-2) of sulfated galactan crude extracts and main fractions obtained from two red seaweeds collected in Brazil, Gymnogongrus griffithsiae and Cryptonemia crenulata. Most of the eighteen tested products, including homogeneous kappa/iota/nu carrageenan and DL-galactan hybrid, exhibited antiherpetic activity with inhibitory concentration 50% (IC50) values in the range 0.5-5.6 microg/ml, as determined in a virus plaque reduction assay in Vero cells. The galactans lacked cytotoxic effects and showed a broad spectrum of antiviral activity against HSV-1 and HSV-2. No direct virus inactivation was observed after virion treatment with the galactans. The mode of action of these compounds could be mainly ascribed to an inhibitory effect on virus adsorption. Most importantly, a significant protection against a murine vaginal infection with HSV-2 was afforded by topical treatment with the sulfated galactans.
Gary W Saunders - One of the best experts on this subject based on the ideXlab platform.
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a revision of the genus Cryptonemia halymeniaceae rhodophyta in bermuda western atlantic ocean including five new species and c bermudensis collins m howe comb nov
European Journal of Phycology, 2018Co-Authors: Craig W Schneider, Christopher E Lane, Gary W SaundersAbstract:Cryptonemia specimens collected in Bermuda over the past two decades were analysed using gene sequences encoding the large subunit of the nuclear ribosomal DNA and the large subunit of RuBisCO as g...
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crebradomus and dissimularia new genera in the family chondrymeniaceae gigartinales rhodophyta from the central southern and western pacific ocean
Phycologia, 2014Co-Authors: Gerald T Kraft, Gary W SaundersAbstract:Two new genera of tropical-/subtropical-Pacific macroalgae are proposed. The monotypic Crebradomus gen. nov., based on C. gongylocarpus sp. nov., is restricted to Lord Howe Island in the southern Australasian-Pacific Ocean. Dissimularia gen. nov. consists of the type species, D. dactylocarpa sp. nov., from its Lord Howe Island type locality, as well as from the Hawaiian Islands, Guam and possibly Burma and the southern Great Barrier Reef, plus three geographically restricted, virtually cryptic species from small islands or atolls in Samoa and Micronesia. The long-problematical ‘Cryptonemia? umbraticola' is shown on the basis of molecular studies of recent collections from its type locality, remote Palmyra Atoll, to represent a distinct species of Dissimularia, D. umbraticola comb. nov., with D. tauensis sp. nov. and D. withallii sp. nov. from Tau and Jarvis Islands, respectively, also belonging to this complex. Morphological features common to these taxa included turf-like, often imbricate thin blades of ...
Alberto S. Cerezo - One of the best experts on this subject based on the ideXlab platform.
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galactans from Cryptonemia species part ii studies on the system of galactans of Cryptonemia seminervis halymeniales and on the structure of major fractions
Carbohydrate Research, 2009Co-Authors: Rosiane G.m. Zibetti, Miguel D. Noseda, Maria Eugênia R. Duarte, Franciely G Colodi, Diogo R B Ducatti, Luciana G Ferreira, Marco Andre Cardoso, Alberto S. CerezoAbstract:Abstract Cryptonemia seminervis biosynthesizes a family of d , l -hybrid galactans based on the classical 3-linked β- d -galactopyranosyl→4-linked α- d - and α- l -galactopyranosyl alternating sequence (A-units→B-units) with major amounts of α- d - and α- l -galactose and 3,6-anhydro- d - and l -galactose and lesser percentages of 3,6-anhydro-2-O-methyl- l -galactose, 2-O-methyl-, 4-O-methyl- and 6-O-methylgalactoses. The dispersion of structures in this family is based on five structural factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and glycosyl side-chain (4-O-methyl galactopyranosyl and/or xylosyl); (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio d , l -galactoses and d , l -3,6-anhydrogalactoses also in the B-units, (d) the formation of diads and (e) the sequence of the diads in the linear backbone. Considering these variables it is not unexpected to find in the fractions studied at least 18 structural units producing highly complex structures. Structural studies carried out in two major fractions (S2S-3 and S2S-4) showed that these galactans were formed mainly by β- d -galactopyranosyl 2-sulfate (20 and 11.9 mol %), β- d -galactopyranosyl 2-sulfate 4,6-O-(1′-carboxyethylidene) (8.9 and 6.0 mol %) and β- d -galactopyranosyl 2,6-sulfate (5.4 and 18.6 mol %), together with 3,6-anhydro-α- l -galactopyranosyl (11.4 and 7.3 mol %) and 3,6-anhydro-α- l -galactopyranosyl 2-sulfate (4.9 and 15.4 mol %) and minor quantities of 12–15 other structural units. Preparative alkaline treatment carried out on fraction (S2S-3) produced a quantitative formation of 3,6-anhydro α- l -galactopyranosyl units from precursor units (α- l -galactose 6-sulfate and α- l -galactose 2,6-sulfate). Kinetic studies on this 3,6-anhydro cyclization show a rate constant of 5.2 × 104 s−1 indicating diads of the type G→L6S/2,6S. Data from chemical, spectroscopic and kinetic studies suggest that, in S2S-3, the agaran block in the d , l -hybrid galactan is composed of the following diads: G(6R)→L6S/2,6S and G2S(P)(2,6S)→LA(2S)(2R)(2M) and the carrageenan block of G2S(P)→D(2S)(2,3S)(3S)(3,6S) in a molar ratio of agaran to carrageenan structures of ∼2:1.
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The system of galactans from Cryptonemia crenulata (Halymeniaceae, Halymeniales) and the structure of two major fractions. Kinetic studies on the alkaline cyclization of the unusual diad G2S-->D(L)6S.
Carbohydrate research, 2005Co-Authors: Rosiane G.m. Zibetti, Miguel D. Noseda, Alberto S. Cerezo, Maria Eugênia R. DuarteAbstract:Cryptonemia crenulata biosynthesizes a family of dl-hybrid galactans that are based on the classical 3-linked beta-d-galactopyranosyl-->4-linked alpha-galactopyranosyl alternating sequence (A-units-->B-units). The dispersion of structures in these galactans is based on four factors, namely: (a) the amount and position of substituent groups as sulfate (major), pyruvic acid ketals, methoxyl and side substituents of beta-D-xylose and/or beta-D-galactose; (b) the ratio galactose/3,6-anhydrogalactose in the B-units; (c) the ratio D-/L-galactoses and 3,6-anhydrogalactoses also in the B-units and (d) the sequence of the diads in the linear backbone. Alkali treatment carried out on the major fraction produced a nearly quantitative formation of 3,6-anhydrogalactose units from precursor units (alpha-galactose 6-sulfate (major) and alpha-galactose 2,6-sulfate, minor). Kinetic studies show a rate constant, for the diad G2S-D(L) 6-S, of 1.7 x 10(4)s(-1) indicating a reaction faster than in lambda-carrageenans but slower than in porphyrans.