- A sulfated galactan with antioxidant capacity from the green variant of tetrasporic Gigartina skottsbergii (Gigartinales, Rhodophyta)
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The water soluble polysaccharide produced by the green variant of tetrasporic Gigartina skottsbergii was found to be composed of d-galactose and sulfate groups in a molar ratio of 1.0:0.65. 1H and 13C NMR spectroscopy studies of the desulfated polysaccharide showed a major backbone structure of alternating 3-linked β-d-galactopyranosyl and 4-linked α-d-galactopyranosyl units, and minor signals ascribed to 3-O-methyl-substitution on the latter unit. Ethylation analysis of the polysaccharide indicated that the sulfate groups are mainly located at position O-2 of 4-linked α-d-galactopyranosyl residue and partially located at positions O-6 of the same unit and at position O-2 of 3-linked β-d-galactopyranosyl residue, and confirmed the presence of 3-O-methyl-galactose in minor amounts (4.4%). The sulfated d-galactan presents a similar structure to λ carrageenan but with much lower sulfation at position O-6 of the α-residue and at position O-2 of β-residue. The antioxidant capacity of the sulfated d-galactan was evaluated by the peroxyl radicals (ORAC method), hydroxyl radicals, chelating activity, and ABTS + assays. Kinetic results obtained in these assays were compared with those obtained for the commercial λ carrageenan. The antioxidant activity toward peroxyl radicals was higher for commercial λ carrageenan, this agrees with its higher content of sulfate group. The kinetics of the reaction of both polysaccharides with hydroxyl and ABTS+ radicals showed a complex mechanism, but the antioxidant activity was higher for the polysaccharide from the green variant of tetrasporic Gigartina skottsbergii.
- Barahona, Tamara,Encinas, María V.,Mansilla, Andrés,Matsuhiro, Betty,Zú?iga, Elisa A.
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experimental part
p. 114 - 120
(2012/03/22)
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- Distribution of methyl substituents over branched and linear regions in methylated starches
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Granular potato starch and amylopectin potato starch were methylated in aqueous suspension to molar substitutions (MS) up to 0.29. A method was developed to determine the MS of both branched and linear regions. After exhaustive digestion of the methylated starches with α-amylase, the highly branched fraction with a degree of polymerisation (DP) > 8 was separated from the linear oligomers by selective precipitation of the former in methanol. The substitution levels of branched and linear regions were determined. It was found that methylation takes place preferably at the branched regions of amylopectin and that amylose is higher substituted than linear regions of amylopectin. The distribution of methyl substituents in trimers and tetramers was determined by FABMS and compared to the outcome of a statistically random distribution. The results provided evidence for heterogeneous substituent distributions. Quantification of the degree of heterogeneity of the branched and linear regions showed a much larger deviation from random distribution in the linear regions. Copyright (C) 1998 Elsevier Science Ltd.
- Van Der Burgt, Yuri E.M.,Bergsma, Jack,Bleeker, Ido P.,Mijland, Paul J.H.C.,Van Der Kerk-Van Hoof, Anca,Kamerling, Johannis P.,Vliegenthart, Johannes F.G.
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p. 201 - 208
(2007/10/03)
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- The Synthesis and Reactivity of Cyclic Thiocarbonates Derived from Some Carbohydrate 1,2-Diols
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The attempted synthesis of several carbohydrate 1,2-diols is reported, together with the transformation of two of these diols into cyclic thiocarbonates, namely 4,6-O-benzylidene-3-O-methyl-1,2-O-thiocarbonyl-α-D-glucose and 3,4-O-isopropylidene-1,2-O-thiocarbonyl-β-D-arabinose.The treatment of these thiocarbonates, and a furanose 1,2-thiocarbonate previously prepared by Mukaiyama, with methyl halides and with tributyltin hydride is discussed.A single-crystal X-ray diffraction study of 3,4-O-isopropylidene-1,2-O)-thiocarbonyl-β-D-arabinose is recorded.
- Patroni, Joseph J.,Stick, Robert V.,Tilbrook, D. Matthew G.,Skelton, Brian W.,White, Allan H.
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p. 2127 - 2141
(2007/10/02)
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- GLYCOSIDES OF MARINE INVERTEBRATES. XXVI. HOLOTHURIN A FROM THE PACIFIC OCEAN HOLOTHURIAN Holothuria squamifera. ISOLATION OF THE NATIVE AGLYCONE
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The known triterpene tetraoside holothurin A has been isolated from the Pacific Ocean holothurian Holothuria squamifera.By using two independent methods - enzymatic cleavage and two-stage Smith degradation - 22,25-epoxyholost-9(11)-ene-3β,12α,17α-triol, C30H46O6, which is the native aglycone of holothurin A, was obtained.The structure of the native aglycone has been established on the basis of the results of IR, mass, and PMR spectroscopy.
- Ivanova, N. S.,Smetanina, O. F.,Kuznetsova, T. A.
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p. 424 - 426
(2007/10/02)
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- TRITERPENE GLYCOSIDES OF Salsola micranthera. II. THE STRUCTURE OF SALSOLOSIDE E
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A new triterpene glycoside - salsoloside E - has been isolated from the epigeal part of the plant Salsola micranthera Botsch. family Chenopodiaceae.On the basis of chemical transformations and physicochemical characteristics its structure has been established as oleanoic acid 28-O-β-D-glucopyranoside 3-O-2)>4)>-β-D-glucuronopyranoside>.
- Annaev, Ch.,Isamukhamedova, M.,Abubakirov, N. K.
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- TRITERPENE GLYCOSIDES OF Climacoptera transoxana. III. THE STRUCTURES OF COPTEROSIDES E AND F
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New triterpene glycosides have been isolated from the epigeal part of Climacoptera transoxana (Iljin) Botsch. - copterosides E and F.According to chemical transformations and physicochemical characteristics, copteroside E has the structure of oleanolic acid 28-O-β-D-glucopyranoside 3-O-2)>-4)>-β-D-glucuronopyranoside> and copteroside F that of hederagenin 28-O-β-D-glucopyranoside 3-O-2)>-4)>-β-D-glucopyranoside>.
- Annaev, Ch.,Isaev, M. I.,Abubakirov, N. K.
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p. 560 - 564
(2007/10/02)
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- The galactan sulphate of the red alga Polysiphonia lanosa.
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The structure of the galactan sulphate of P. lanosa has been established by a combination of methylation, treatment with alkali, and partial methanolysis of the alkali-treated polysaccharide to give derivatives of agarobiose. The polysaccharide belongs to the agar class, in which 3-linked derivatives of beta-D-galactose alternate with 4-linked derivatives of alpha-L-galactose in a repeating sequence. In addition to D-galactose itself, the 3-linked units include 6-O-methyl-D-galactose, D-galactose 6-sulphate, and a hitherto unreported unit, 6-O-methyl-D-galactose 4-sulphate. The 4-linked units include L-galactose 6-sulphate, 2-O-methyl-L-galactose 6-sulphate, and 3,6-anhydro-L-galactose.
- Batey,Turvey
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p. 133 - 143
(2007/10/07)
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