Vitamin B12 Phosphate Conjugation and Its Effect on Binding to the Human B12‐Binding Proteins Intrinsic Factor and Haptocorrin

The binding of vitamin B₁₂ derivatives to human B₁₂ transporter proteins is strongly influenced by the type and site of modification of the cobalamin original structure. We have prepared the first cobalamin derivative modified at the phosphate moiety. The reaction conditions were fully optimized and its limitations examined. The resulting derivatives, particularly those bearing terminal alkyne and azide groups, were isolated and used in copper‐catalyzed alkyne–azide cycloaddition reactions (CuAAC). Their sensitivity towards light revealed their potential as photocleavable molecules. The binding abilities of selected derivatives were examined and compared with cyanocobalamin. The interaction of the alkylated derivatives with haptocorrin was less affected than the interaction with intrinsic factor. Furthermore, the configuration of the phosphate moiety was irrelevant to the binding process.     

高效液相色谱法同时测定秋葵干蔬中的脂溶性维生素A、E、K3

建立了同时测定秋葵干蔬中脂溶性维生素A、E、K3的反相高效液相色谱法.样品皂化后,采用C18色谱柱(150 mm×4.6 mm,5μm i.d.)进行分离,以甲醇为流动相,流速1.0 mL/min,二极管阵列检测器(DAD)在325、290、244 nm波长下同时检测,外标法定量.结果表明,脂溶性维生素A、E、K3在0...     

Replacement of the Cobalt Center of Vitamin B12 by Nickel: Nibalamin and Nibyric Acid Prepared from Metal-Free B12 Ligands Hydrogenobalamin and Hydrogenobyric Acid

The (formal) replacement of Co in cobalamin ( Cbl ) by Ni^II generates nibalamin ( Nibl ), a new transition-metal analogue of vitamin B₁₂. Described here is Nibl , synthesized by incorporation of a Ni^II ion into the metal-free B₁₂ ligand hydrogenobalamin ( Hbl ), itself prepared from hydrogenobyric acid ( Hby ). The related Ni^II corrin nibyric acid ( Niby ) was similarly synthesized from Hby , the metal-free cobyric acid ligand. The solution structures of Hbl , and Niby and Nibl , were characterized by spectroscopic studies. Hbl features two inner protons bound at N2 and N4 of the corrin ligand, as discovered in Hby . X-ray analysis of Niby shows the structural adaptation of the corrin ligand to Ni^II ions and the coordination behavior of Ni^II. The diamagnetic Niby and Nibl , and corresponding isoelectronic Co^I corrins, were deduced to be isostructural. Nibl is a structural mimic of four-coordinate base-off Cbls , as verified by its ability to act as a strong inhibitor of bacterial adenosyltransferase.     

Tailored Synthesis of Various Nanomaterials by Using a Graphene‐Oxide‐Based Gel as a Nanoreactor and Nanohybrid‐Catalyzed CC Bond Formation

New graphene oxide (GO)‐based hydrogels that contain vitamin B₂/B₁₂ and vitamin C (ascorbic acid) have been synthesized in water (at neutral pH value). These gel‐based soft materials have been used to synthesize various metal nanoparticles, including Au, Ag, and Pd nanoparticles, as well as nanoparticle‐containing reduced graphene oxide (RGO)‐based nanohybrid systems. This result indicates that GO‐based gels can be used as versatile reactors for the synthesis of different nanomaterials and hybrid systems on the nanoscale. Moreover, the RGO‐based nanohybrid hydrogel with Pd nanoparticles was used as an efficient catalyst for C? C bond‐formation reactions with good yields and showed high recyclability in Suzuki–Miyaura coupling reactions.     

Determination of target fat‐soluble micronutrients in rainbow trout's muscle and liver tissues by liquid chromatography with diode array‐tandem mass spectrometry detection

This paper describes an analytical approach, based on LC‐diode array detector‐MS/MS (LC‐DAD‐MS/MS), for characterizing the fat‐soluble micronutrient fraction in rainbow trout (Oncorhynchus mykiss ). Two different procedures were applied to isolate the analytes from liver and muscle tissue: overnight cold saponification to hydrolyze bound forms and to simplify the analysis; matrix solid‐phase dispersion to avoid artifacts and to maintain unaltered the naturally occurring forms. Analytes were separated on a C₃₀ analytical column by using a nonaqueous reversed mobile phase compatible with the atmospheric pressure chemical ionization. Compared to other works, the most relevant advantage of the here illustrated method is the large amount of information obtained with few analytical steps: nine fat‐soluble vitamins (3,4‐dehydroretinol, retinol, cholecalciferol, ergocalciferol, α‐tocopherol, γ‐tocopherol, δ‐tocopherol, phylloquinone, and menaquinone‐4) and eight carotenoids (all‐trans ‐lutein, all‐trans ‐astaxanthin, all‐trans ‐zeaxanthin, all‐trans ‐β‐cryptoxanthin, all‐trans ‐canthaxanthin, all‐trans ‐ζ‐carotene, all‐trans ‐β‐carotene, and all‐trans ‐γ‐carotene) were quantified after the method validation, while other untargeted carotenoids were tentatively identified by exploiting the identification power of the LC‐DAD‐MS/MS hyphenation.     

Preparation of a novel carboxyl stationary phase by “thiol‐ene” click chemistry for hydrophilic interaction chromatography

A novel carboxyl‐bonded silica stationary phase was prepared by “thiol‐ene” click chemistry. The resultant Thiol‐Click‐COOH phase was evaluated under hydrophilic interaction liquid chromatography (HILIC) mobile phase conditions. A comparison of the chromatographic performance of Thiol‐Click‐COOH and pure silica columns was performed according to the retention behaviors of analytes and the charged state of the stationary phases. The results indicated that the newly developed Thiol‐Click‐COOH column has a higher surface charge and stronger hydrophilicity than the pure silica column. Furthermore, the chromatographic behaviors of five nucleosides on the Thiol‐Click‐COOH phase were investigated in detail. Finally, a good separation of 13 nucleosides and bases, and four water‐soluble vitamins was achieved.     

Simultaneous square-wave voltammetric determination of riboflavin and folic acid in pharmaceutical preparations

The square-wave voltammetric (SWV) behaviour of riboflavin and folic acid was studied at a static mercury drop electrode by square wave voltammetry. In 0.05M KCl (pH 5.89) a cathodic scan gave peaks at — 0.56 and — 0.87 V vs. Ag/AgCl for riboflavin and folic acid, respectively. The reduction peak currents are linearly dependent on the concentration of vitamins. Both vitamins can be simultaneously determined from the same voltammogram. The method proposed for the determination of riboflavin and folic acid in multivitamin tablets is very simple, rapid and does not involve time-consuming separation steps. The average contents of riboflavin and folic acid were found to be 14.8 ± 1.26% and 1.46 ± 2.66%, for tablet A and 9.86 ±1.40% and 1.47 ± 2.0% for tablet B, respectively.     

HPLC法测定库克Noni果汁中游离态水溶性维生素

采用HPLC法测定Noni果汁中游离态的抗坏血酸（Vc）、硫胺素（VB1）和烟酰胺（VB5），其测定条件为：色谱柱为Alhima C18柱，流动相为甲醇-0．01％磷酸（3：7，V／V），流速为1．0mL／min，进样量为20μL，柱温为室温，采用二极管阵列检测器在251nm下检测。在上述色谱测定条件下三种维生素能得到良好分离。结果表明，该方法灵敏度高，定量准确，重现性好，回收率高。昕测Noni果汁中三种维生素的含量分别为：Vc0．354mg／mL，VB10．0663mg／mL，VB50．131mg／mL。说明Noni果汁中三种必需维生素含量丰富，可作为维生素缺乏的营养补充剂；所建立的测定方法可作为一种Noni果汁生产质量控制方法。