- A comparative study of the neutral and acidic polysaccharides from Allium macrostemon Bunge
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Neutral and acidic polysaccharides, named AMP40N and AMP40S respectively, were isolated and purified from the dried bulbs of Allium macrostemon Bunge. Both of them showed a single and symmetrically sharp peak, indicating they were homogeneous polysaccharides. Molecular weights of AMP40N and AMP40S were determined to be 18.2 and 105.1 kDa, respectively. AMP40N was composed of arabinose and glucose, while AMP40S was composed of rhamnose, arabinose, glucose and galactose and a certain amount of uronic acid. FT-IR, periodic acid oxidation, Smith degradation, methylation and GC-MS analysis revealed that non-reducing terminal and →2,6)-Glc-(1→ existed in AMP40N and AMP40S. The glycosidic linkage of arabinose in AMP40N was →2)-Ara-(1→, whereas it was Ara-(1→ in AMP40S. AMP40S had (1→2)-linked l-rhamnose residue. Both AMP40N and AMP40S exhibited strong anti-tumor potential against human gastric carcinoma cells BGC-823, in particular, AMP40S presented significantly higher inhibitory rate of 85.94% than AMP40N of 52.63%.
- Zhang, Zhanjun,Wang, Fuhua,Wang, Mingchun,Ma, Liping,Ye, Hong,Zeng, Xiaoxiong
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p. 980 - 987
(2015/01/09)
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- Asymmetric organocatalytic formation of protected and unprotected tetroses under potentially prebiotic conditions
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Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose under potentially prebiotic conditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (l)-proline yield (l)-tetroses, esters of (l)-leucine, (l)-alanine and (l)-valine generate (d)-tetroses, offering the potential to account for the link between natural (l)-amino acids and natural (d)-sugars. The effect of pH and NaCl on the yields and enantioselectivities was also investigated and was shown to be significant, with the optimal enantioselectivities occurring at pH 7.
- Burroughs, Laurence,Clarke, Paul A.,Forintos, Henrietta,Gilks, James A. R.,Hayes, Christopher J.,Vale, Matthew E.,Wade, William,Zbytniewski, Myriam
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supporting information; experimental part
p. 1565 - 1570
(2012/04/05)
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- Efficient asymmetric organocatalytic formation of erythrose and threose under aqueous conditions
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Esters of proteinogenic amino acids efficiently catalyse the formation of erythrose and threose under aqueous conditions in the highest yields and enantioselectivities yet reported. Remarkably while esters of (l)-proline yield (l)-carbohydrates, esters of (l)-leucine and (l)-alanine generate (d)-carbohydrates, offering the potential to account for the prebiotic link between natural (l)-amino acids and natural (d)-sugars.
- Burroughs, Laurence,Vale, Matthew E.,Gilks, James A. R.,Forintos, Henrietta,Hayes, Christopher J.,Clarke, Paul A.
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supporting information; experimental part
p. 4776 - 4778
(2010/09/05)
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- Prebiotic carbohydrate synthesis: Zinc-proline catalyzes direct aqueous aldol reactions of α-hydroxy aldehydes and ketones
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Zn-proline catalyzed aldolisation of glycoladehyde gave mainly tetroses whereas in the cross-aldolisation of glycoladehyde and rac-glyceraldehyde, pentoses accounted for 60% of the sugars formed with 20% of ribose. The Royal Society of Chemistry 2005.
- Kofoed, Jacob,Reymond, Jean-Louis,Darbre, Tamis
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p. 1850 - 1855
(2007/10/03)
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- EQUILIBRATION OF ALDITOL ANHYDRIDES IN ACETIC ACID
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Dehydration of pentitols in acetic acid containing an acidic catalyst parallels that in aqueous sulfuric acid; 1,4(2,5)-dehydration occurs with inversion of configuration at C-2 or C-4.Acetylated alditols undergo similar processes via intermediates having free hydroxyl groups.Configurational inversion of 1,4- or 1,5-anhydroalditols is attributed to intermediate acyloxonium ions that are also proposed as intermediates in the structural isomerisation.Drastic treatment of each alditol gives equilibrium mixtures.The equilibrium concentrations are used to calculate free-energy differences.
- Wisniewski, Andrzej,Gajdus, Jerzy,Sokolowski, Janusz,Szafranek, Janusz
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