Refernces
10.1021/ac034876a
The study presents the development of a biosensor-based assay for the quantification of riboflavin (Rf) in milk samples using surface plasmon resonance (SPR) technology. The assay involves the indirect measurement of Rf by detecting the excess of riboflavin binding protein (RBP) that remains free after complexation with Rf molecules originally present in the sample. The sensor chip is modified with covalently immobilized Rf to bind the excess RBP. The method involves a chemical modification to introduce a reactive ester group on the Rf molecule for immobilization on the chip surface. Calibration solutions are prepared by mixing Rf standard solutions with an optimized concentration of RBP, and the Rf content in milk samples is measured by comparing the response against the calibration. The results are comparable to those obtained from an official HPLC-fluorescence procedure, with a limit of quantification determined to be 234 μg/L and a limit of detection to 70 μg/L. The study demonstrates the potential of SPR-based biosensors as a competitive alternative to traditional analytical techniques for the determination of riboflavin in food samples.
10.1021/ol034530m
The research explores the nonenzymatic synthesis of the 5,6-dimethylbenzimidazole (DMB) ligand of vitamin B12 from riboflavin through an oxidative cascade under physiological conditions. Coenzyme B12, also known as vitamin B12, is a complex cobalt-containing vitamin essential for various biological processes. 5,6-Dimethylbenzimidazole (DMB) is an organic compound that serves as one of the axial ligands of coenzyme B12. Riboflavin, also known as vitamin B2, is a precursor in the biosynthesis of DMB in the study. It is a water-soluble vitamin that plays a vital role in cellular respiration and energy production. The study demonstrates that DMB can be formed from diaminobenzene intermediates via a series of oxidation steps, including the formation of bisimines and subsequent tautomerization, cyclization, and aromatization.
10.1002/cmdc.201000225
The research investigates the interaction between artemisinins, a class of compounds derived from the plant Artemisia annua and used in the treatment of malaria, and redox-active substrates such as leucomethylene blue and dihydroflavins. The study aims to understand the molecular mechanism by which artemisinins exert their antimalarial effects, particularly their ability to generate reactive oxygen species (ROS) and interfere with the redox balance within the malaria parasite. The researchers found that artemisinins can act as both one-electron transfer agents and two-electron acceptors, potentially disrupting the function of flavin cofactors in redox-active enzymes within the parasite. The chemicals used in the study include artemisinins, methylene blue, ascorbic acid, N-benzyldihydronicotinamide (BNAH), riboflavin, flavin mononucleotide (FMN), and flavin adenine dinucleotide (FAD), among others. The conclusions suggest that artemisinins may act as antimalarial drugs by perturbing the redox balance within the malaria parasite, and their selective potency may be due to differences in sensitivity between parasite and human glutathione reductase. This research provides insights into the potential mechanisms of artemisinin resistance in malaria parasites and could inform the development of new antimalarial drugs.
10.1021/jo00942a048
The research presents an improved general synthesis of aporphines via Pschorr cyclization of 1-(2’-aminobenzyl)-7-hydroxy-l,2,3,4-tetrahydroisoquinolines. The key chemicals involved in this research include o-nitrotoluenes (2a-e), 6-methoxy-7-hydroxy-3,4-dihydroisoquinolinium methiodide, KO-t-Bu, Pd/C, Zn-H2SO4, diazomethane, and copper powder. The synthesis involves several steps: condensation of o-nitrotoluenes with 6-methoxy-7-hydroxy-3,4-dihydroisoquinolinium methiodide in the presence of KO-t-Bu to form 1-(2’-nitrobenzyl)-7-hydroxy-1,2,3,4-tetrahydroisoquinolines (3a-e); reduction of these compounds with Pd/C or Zn-H2SO4 to obtain aminophenols (4a-f); and cyclization of the aminophenols to form 1-hydroxyaporphines (5a-f) using diazotization and copper powder. The final products include thalicmidine (5g), nuciferine (6a), glaucine (6g), and the thalicarpine precursor 6e. The synthesis is notable for achieving the highest yields reported to date for these compounds.
