The Experts below are selected from a list of 27528 Experts worldwide ranked by ideXlab platform
Sylvia Urban - One of the best experts on this subject based on the ideXlab platform.
-
Phytochemical studies of the southern Australian Marine Alga, Laurencia elata
Phytochemistry, 2011Co-Authors: Daniel A. Dias, Sylvia UrbanAbstract:Chemical profiling of the southern Australian Marine Alga Laurencia elata (Rhodomelaceae) employing on-flow and stop-flow HPLC–NMR methodology followed by off-line chemical investigations resulted in the isolation of two C16 chamigrenes, cycloelatanene A and B together with three previously reported sesquiterpenes, (3Z)-chlorofucin, pacifenol and elatenyne. The chemical structures were elucidated via detailed spectroscopic analyses.
-
Phytochemical analysis of the Southern Australian Marine Alga, Plocamium mertensii using HPLC‐NMR
Phytochemical analysis : PCA, 2008Co-Authors: Daniel A. Dias, Sylvia UrbanAbstract:Introduction: Over the last decade HPLC-NMR has become a robust analytical technique that has been applied to a wide range of studies, particularly plant extracts. There have been only a few applications of the use of HPLC-NMR to profile Marine natural product extracts and no studies involving Marine Algae. The Marine Alga selected for this study belongs to the genus Plocamium, which is a well known source of polyhalogenated monoterpenes. Objective: To chemically profile the Marine Alga P. mertensii, using a combination of on-line (HPLC-NMR) and off-line approaches. Methodology: P. mertensii was extracted with 3:1 methanol-dichloromethane and subsequently partitioned into dichloromethane and methanol-soluble fractions. The methanol partition was exclusively profiled by HPLC-NMR (on-flow, stop-flow and time-slice experiments) whilst the dichloromethane partition was investigated by conventional isolation and purification procedures. Results: HPLC-NMR analysis of the methanol partition partially identified the presence of the major compounds 7, 13, 27 and 37, the structures of which were unequivocally elucidated by off-line characterisation of the dichloromethane partition. Two additional minor metabolites (3 and 8) present in the dichloromethane partition were only tentatively identified as these co-occurred in a mixture with compounds 7 and 13. As a result of this study a number of chemical shift reassignments were made for compound 37. Conclusion: This is one of the few reports describing the application of HPLC-NMR to rapidly proftle or dereplicate a Marine organism and the first application of HPLC-NMR to successfully profile the chemistry of a Marine Alga.
Daniel A. Dias - One of the best experts on this subject based on the ideXlab platform.
-
Phytochemical studies of the southern Australian Marine Alga, Laurencia elata
Phytochemistry, 2011Co-Authors: Daniel A. Dias, Sylvia UrbanAbstract:Chemical profiling of the southern Australian Marine Alga Laurencia elata (Rhodomelaceae) employing on-flow and stop-flow HPLC–NMR methodology followed by off-line chemical investigations resulted in the isolation of two C16 chamigrenes, cycloelatanene A and B together with three previously reported sesquiterpenes, (3Z)-chlorofucin, pacifenol and elatenyne. The chemical structures were elucidated via detailed spectroscopic analyses.
-
Phytochemical analysis of the Southern Australian Marine Alga, Plocamium mertensii using HPLC‐NMR
Phytochemical analysis : PCA, 2008Co-Authors: Daniel A. Dias, Sylvia UrbanAbstract:Introduction: Over the last decade HPLC-NMR has become a robust analytical technique that has been applied to a wide range of studies, particularly plant extracts. There have been only a few applications of the use of HPLC-NMR to profile Marine natural product extracts and no studies involving Marine Algae. The Marine Alga selected for this study belongs to the genus Plocamium, which is a well known source of polyhalogenated monoterpenes. Objective: To chemically profile the Marine Alga P. mertensii, using a combination of on-line (HPLC-NMR) and off-line approaches. Methodology: P. mertensii was extracted with 3:1 methanol-dichloromethane and subsequently partitioned into dichloromethane and methanol-soluble fractions. The methanol partition was exclusively profiled by HPLC-NMR (on-flow, stop-flow and time-slice experiments) whilst the dichloromethane partition was investigated by conventional isolation and purification procedures. Results: HPLC-NMR analysis of the methanol partition partially identified the presence of the major compounds 7, 13, 27 and 37, the structures of which were unequivocally elucidated by off-line characterisation of the dichloromethane partition. Two additional minor metabolites (3 and 8) present in the dichloromethane partition were only tentatively identified as these co-occurred in a mixture with compounds 7 and 13. As a result of this study a number of chemical shift reassignments were made for compound 37. Conclusion: This is one of the few reports describing the application of HPLC-NMR to rapidly proftle or dereplicate a Marine organism and the first application of HPLC-NMR to successfully profile the chemistry of a Marine Alga.
Alexandre Holanda Sampaio - One of the best experts on this subject based on the ideXlab platform.
-
Red Marine Alga Bryothamnion triquetrum lectin induces endothelium-dependent relaxation of the rat aorta via release of nitric oxide.
The Journal of pharmacy and pharmacology, 2004Co-Authors: Ricardo F. Lima, Alexandre Holanda Sampaio, David N. Criddle, Emmanuel P. Souza, Kyria S. Nascimento, Benildo Sousa Cavada, Ana Maria Sampaio AssreuyAbstract:We have investigated the vascular relaxant effects of the lectin from a red Marine Alga Bryothamnion triquetrum (BTL), in particular, the endothelial-dependency and the participation of a specific glycoprotein-binding site. BTL (1-100 microg mL(-1)) was applied to rat isolated aortic rings, with or without endothelium, tonically precontracted with phenylephrine (0.1 microM). Endothelium-dependent relaxation was assessed in the presence of indometacin (10 microM), L-nitro arginine methyl ester (L-NAME, 100 microM) and tetraethylammonium (TEA, 500 microM). For the involvement of the glycoprotein-binding site, BTL was assayed in presence of mucin (300 microg mL(-1)) or N-acetyl D-glucosamine (GlcNAc; 300 microg mL(-1)), a specific and non-specific lectin-binding sugar, respectively. BTL fully and concentration dependently relaxed preparations that possessed an intact endothelium (IC50 (concn producing 50% contraction) = 12.1 +/- 1.6 microg mL(-1)), whereas no significant relaxation was observed in endothelial-denuded tissue. L-NAME, but not indometacin or TEA, completely inhibited the lectin relaxation, suggesting the involvement of nitric oxide (NO). The lectin in association with mucin, but not with GlcNAc, inhibited BTL-induced relaxation, implicating the involvement of the lectin binding site. Our data suggest that the relaxant effect of the red Marine Alga Bryothamnion triquetrumlectin on isolated aorta occurs via interaction with a specific lectin-binding site on the endothelium, resulting in a release of NO.
-
A galactose-specific lectin from the red Marine Alga Ptilota filicina
Phytochemistry, 1998Co-Authors: Alexandre Holanda Sampaio, David J. Rogers, Clive J. BarwellAbstract:Abstract A lectin from the red Marine Alga Ptilota filicina (PFL) was isolated by affinity chromatography on cross-linked guar gum. PFL agglutinated native and papain-treated human erythrocytes with preference for type O erythrocytes. The lectin was inhibited by galactose and its derivatives. The most potent inhibitors were p -Nitrophenyl- N -acetyl- α - and β- d -galactosaminide. Porcine stomach mucin, bovine submaxillary gland mucin and asialo bovine mucin were also inhibitory. The M r of PFL, determined by gel filtration, was 56,900. SDS-PAGE gave one band with a subunit M r of 19,320, indicating the native protein to be a trimer of apparently identical subunits. PFL was shown to be rich in acidic and hydroxyl amino acids but low in basic amino acids. The ten N -terminal amino acids were Asx-Thr-Lys-Thr-Tyr-Leu-Leu-Ala-.
Clive J. Barwell - One of the best experts on this subject based on the ideXlab platform.
-
A galactose-specific lectin from the red Marine Alga Ptilota filicina
Phytochemistry, 1998Co-Authors: Alexandre Holanda Sampaio, David J. Rogers, Clive J. BarwellAbstract:Abstract A lectin from the red Marine Alga Ptilota filicina (PFL) was isolated by affinity chromatography on cross-linked guar gum. PFL agglutinated native and papain-treated human erythrocytes with preference for type O erythrocytes. The lectin was inhibited by galactose and its derivatives. The most potent inhibitors were p -Nitrophenyl- N -acetyl- α - and β- d -galactosaminide. Porcine stomach mucin, bovine submaxillary gland mucin and asialo bovine mucin were also inhibitory. The M r of PFL, determined by gel filtration, was 56,900. SDS-PAGE gave one band with a subunit M r of 19,320, indicating the native protein to be a trimer of apparently identical subunits. PFL was shown to be rich in acidic and hydroxyl amino acids but low in basic amino acids. The ten N -terminal amino acids were Asx-Thr-Lys-Thr-Tyr-Leu-Leu-Ala-.
Takashi Suzuki - One of the best experts on this subject based on the ideXlab platform.
-
structure and anti dengue virus activity of sulfated polysaccharide from a Marine Alga
Biochemical and Biophysical Research Communications, 2008Co-Authors: Kazuya I.p.j. Hidari, Masato Nagaoka, Naonori Takahashi, Masataka Arihara, Koichi Morita, Takashi SuzukiAbstract:A sulfated polysaccharide, named fucoidan, from the Marine Alga Cladosiphon okamuranus is comprised of carbohydrate units containing glucuronic acid and sulfated fucose residues. Here we found this compound potently inhibits dengue virus type 2 (DEN2) infection. Viral infection was inhibited when DEN2, but not other serotypes, was pretreated with fucoidan. A carboxy-reduced fucoidan derivative in which glucuronic acid was converted to glucose did not inhibit viral infection. Elimination of the sulfated function group from fucoidan significantly attenuated the inhibitory activity on DEN2 infection with <1% fucoidan. DEN2 particles bound exclusively to fucoidan, indicating that fucoidan interacts directly with envelope glycoprotein (EGP) on DEN2. Structure-based analysis suggested that Arg323 of DEN2 EGP, which is conformationally proximal to one of the putative heparin binding residues, Lys310, is critical for the interaction with fucoidan. In conclusion, both the sulfated group and glucuronic acid of fucoidan account for the inhibition of DEN2 infection.
-
Structure and anti-dengue virus activity of sulfated polysaccharide from a Marine Alga.
Biochemical and Biophysical Research Communications, 2008Co-Authors: Kazuya I.p.j. Hidari, Masato Nagaoka, Naonori Takahashi, Masataka Arihara, Koichi Morita, Takashi SuzukiAbstract:A sulfated polysaccharide, named fucoidan, from the Marine Alga Cladosiphon okamuranus is comprised of carbohydrate units containing glucuronic acid and sulfated fucose residues. Here we found this compound potently inhibits dengue virus type 2 (DEN2) infection. Viral infection was inhibited when DEN2, but not other serotypes, was pretreated with fucoidan. A carboxy-reduced fucoidan derivative in which glucuronic acid was converted to glucose did not inhibit viral infection. Elimination of the sulfated function group from fucoidan significantly attenuated the inhibitory activity on DEN2 infection with