Simultaneous Determination of Gallic Acid and Folic Acid in Fruit Juice Samples Using Square Wave Voltammetry at Electrochemically Pretreated Carbon Paste Electrode

An efficient sensor was developed for the simultaneous determination of gallic and folic acid in juice samples using an electrochemically pretreated carbon paste electrode. The electrode was characterized by CV and EIS. The electrochemical behavior of GA and FA was evaluated by CV and SWV. The electrode exhibited high electrocatalytic activity towards GA and FA due to high surface area. Under the optimized condition, linear plots in the ranges of 0.08–13 μM and 0.1 to 15 μM were obtained for GA and FA, respectively. The proposed method was successful for the simultaneous determination of GA and FA in juice samples with satisfactory recovery.     

Improved synthesis of 1,4-dideoxy-1,4-imino-d-galactitol, an inhibitor of E. coli K12 UDP-Gal mutase and mycobacterial galactan biosynthesis

The E. Coli K12 UDP-Gal mutase inhibitor 1 was prepared from d-glucose in 5 steps (42% overall yield). The 4-azido galactose derivative 11, leading to 1, was formed by treatment of galactose dithioacetal 7 with mercuric oxide and mercuric chloride in acetone. To obtain 7, acetal 3 was tosylated or triflated and treated with NaN₃.     

Analytical Scheme Leading to Integrated High-Sensitivity Profiling of Glycosphingolipids Together with <Emphasis Type="Italic">N</Emphasis>- and <Emphasis Type="Italic">O</Emphasis>-Glycans from One Sample

Glycoconjugates are directly or indirectly involved in many biological processes. Due to their complex structures, the structural elucidation of glycans and the exploration of their role in biological systems have been challenging. Glycan pools generated through release from glycoprotein or glycolipid mixtures can often be very complex. For the sake of procedural simplicity, many glycan profiling studies choose to concentrate on a single class of glycoconjugates. In this paper, we demonstrate it feasible to cover glycosphingolipids, N-glycans, and O-glycans isolated from the same sample. Small volumes of human blood serum and ascites fluid as well as small mouse brain tissue samples are sufficient to profile sequentially glycans from all three classes of glycoconjugates and even positively identify some mixture components through MALDI-MS and LC-ESI-MS. The results show that comprehensive glycan profiles can be obtained from the equivalent of 500-μg protein starting material or possibly less. These methodological improvements can help accelerating future glycomic comprehensive studies, especially for precious clinical samples.

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Graphical Abstract Outline of glycan profiling procedures

     

Behaviour of the Primary Nitro Group Under Denitration Conditions

ABSTRACT

Treatment of per-O-acetylated or acetalated glycosylnitromethanes derived from the common hexoses and pentoses with tributyltin hydride and a catalytic amount of a radical initiator [1,1′-azobis(cyclohexanecarbonitrile)] in refluxing benzene easily afforded the corresponding glycosylmethanal oximes in 84-97% yields. Per-O-acetylated C-β-glycopyranosylmethanal oximes were employed for synthesis of versatile C-β-glycopyranosyl cyanides of the β-D-gluco, β-D-manno, β-D-galacto, β-D-xylo, and β-L-rhamno configurations.     

Conversions of Nitroalkyl to Carbonyl Groups in Carbohydrates

Summary.  Since the development of the Sowden methodology in the middle of the twentieth century, several other efficient and complementary methods for the transformation of sugar nitromethyl groups to aldehyde functionalities in their free, hemiacetal, or otherwise derivatized forms have been developed. Hydrogen peroxide oxidation as well as ozonolysis of 1-deoxyalditol-1-nitronates in aqueous solution provide free aldoses, thus presenting alternatives to the well-known Nef reaction. When applied to 2,5- or 2,6-anhydro-1-deoxy-1-nitroalditols, also known also as glycosylnitromethanes, the Nef reaction fails, and the hydrogen peroxide oxidation overoxidizes the expected products to 2,5- or 2,6-anhydroaldonic acids. On the other hand, the ozonolysis of such compounds under pH-controlled conditions results in up to 85% of the interesting glycosylformaldehydes. The Nef reaction carried out in anhydrous low alcohols, however, has revealed a new conversion of glycosylnitromethanes to glycosylmethanal dialkyl acetals, even more interesting C-glycoside synthons. A similar acid-catalyzed methanolysis of 1-deoxyalditol-1-nitronates leads to methyl furanosides. Finally, a treatment of per-O-substituted glycosylnitromethanes with tributyltin hydride in boiling benzene causes their radical reduction under a nearly quantitative formation of glycosylmethanal oximes. Received November 12, 2001. Accepted November 20, 2001