Utility of N-Bromosuccinimide-Water Combination as a Green Reagents for a Validated Indirect Spectrophotometric Determination of Some Antihypertensive Drugs: An Application to Their Monitoring in Marketed Tablets and Capsules.

BACKGROUND: Analytical tests were conducted to investigate the use of N-bromosuccinimide (NBS) as an important, safe analytical reagent for the spectrophotometric detection of therapeutically significant dihydropyridine-based calcium antagonists (DHP), namely nifedipine (NIF) and amlodipine (AML), which have been demonstrated to possess antioxidant activity in vivo and to reduce the intracellular production of reactive oxygen species (ROS). Following the reaction of DHP and NBS in acidic media, the excess NBS was evaluated for the first time by its interaction with P-aminophenol (PAP), which produced a violet-colored product that was detected at 556 nm. OBJECTIVE: The analytical method was performed and validated since different variables disturbing the reaction (concentration of reagent, type and concentration of the selected acid, reaction time and the diluting solvents) were carefully studied and optimized. METHODS: The stoichiometry of the applied reaction was determined by Job's method of continuous variation. Monitoring of these drug dosage forms' content uniformity is a first tool or evidence for their efficacy and safety after their administration. RESULTS: Beer's law was obeyed in the concentration range 1.25-11.0 µg/mL for NIF and 1.25-10.0 µg/mL for AML. The calculated limit of detection (LODs) and limit of quantification (LOQs) for NIF and AML were 0.220, 0.155 µg/mL and 0.519, 0.735 µg/mL, respectively. The precision of the applied method was satisfactory; the RSDs did not exceed 2%. Two greenness assessment tools, the Green Analytical Procedure Index (GAPI) and Analytical Greenness Metric for Sample Preparation (AGREEprep) were used for measuring the environmental friendliness of the recommended method. CONCLUSION: The micro-determinations of content uniformity for NIF and AML in their pharmaceutical dosage forms were extremely comparable with those from official and validated procedures. HIGHLIGHTS: A validated indirect spectrophotometric method for accurate quantification of some 1,4-dihydropyridine drugs using NBS with the aid of PAP. Monitoring of NIF and AML dosage forms' content uniformity as a first tool or evidence for their efficacy and safety after their administration. Greenness evaluation tools, GAPI and AGREEprep, for measuring the environmental friendliness of the recommended method.

Furan-based (photo)oxidation reactions and their application in nucleic acid and protein targeting.

Oligonucleotides (ODNs) find applications as diagnostic and therapeutic tools due to their unique ability to interact, thanks to Watson-Crick base pairing, with a specific DNA or RNA target strand. Although most of the tools available today rely on mere hydrogen bond formation, chemical modifications to enable covalent interstrand-crosslinking (ICL) have been reported, and are gaining a place under the spotlight as they potentially offer a series of advantages over the state of the art, including a higher potency and selectivity. This methodological paper focuses on the use of a pro-reactive furan moiety and its subsequent oxidation for applications in ODN targeting. The design of effective capture and targeting probes to ensure high ICL yields is discussed and the mechanisms underlying the (photo)chemical oxidation of furan are explained. Furthermore, examples of furan-containing DNAs designed for different applications, including DNA-DNA or DNA-RNA ICL and DNA-peptide/protein targeting, are provided. The paper highlights the advantages of using different oxidative chemical triggers, such as N-bromosuccinimide or singlet oxygen, to offer additional selectivity control over the ICL reaction.

A Green Approach to 2-Substituted Benzo- and Naphthothiazoles via N-bromosuccinimide/Bromide-Mediated C(aryl)-S Bond Formation.

2-Substituted benzo- and naphthothiazoles have been conveniently prepared from the intramolecular cyclization of phenylthioureas and activated thiobenzanilides or the coupling of isothiocyanates with amines under mild conditions using N-bromosuccinimide/tetrabutylammonium bromide in 1,2-dimethoxyethane (DME) under ambient conditions. The reactions produce moderate to excellent yields with good functional group tolerance and avoid the use of harsh thermal conditions, corrosive reagents, halogenated solvents, toxic metal salts, and expensive metal catalysts, and are amenable to preparations on a gram-scale.

An Improved Protocol for the Stereoselective Synthesis of ß-d-Glycosyl Fluorides from 2-O-Acyl Thioglycosides.

A safe and operationally simple protocol for the preparation of ß-d-glycosyl fluorides is presented. We demonstrate that a precise combination of XtalFluor-M, N-bromosuccinimide, and Et3N·3HF can mediate facile, high-yielding, and diastereoselective conversions of 2-O-acyl thioglycosides to ß-d- and other 1,2-trans glycosyl fluorides. The key roles of these reagents are dissected in this work, as is the impact of their interplay on the fluorination stereoselectivity.

SiO2-supported HClO4 catalyzed synthesis of (Z)-thiazolylhydrazonoindolin-2-ones and their electrochemical properties.

In this paper, an environmentally benign silica-supported perchloric acid (HClO4-SiO2) catalyzed green FCDR strategy has been developed for the synthesis of (Z)-THIs (6) with high stereospecificity via an intramolecular hydrogen bond (IHB) directed approach, involving the reaction of methyl ketones (1), N-bromosuccinimide (NBS) (2), isatins (4) and thiosemicarbazide (5) in ethanol at reflux temperature for 45-60 min in one-pot. The reaction proceeds through the construction of C-Br (α-bromination), C-S & C-N (heterocyclization), and CN (condensation) bonds in one pot. The absolute structure of the compound (Z)-3-(2-(4-(4-bromophenyl)thiazol-2-yl)hydrazono)indolin-2-one (6e) has been confirmed by single-crystal XRD analysis. Further, the role of IHB on Z-configuration of the synthesized (Z)-THIs is proved by single-crystal XRD and 1H NMR studies. Wide substrate scope, good functional group tolerance, scalability, improved safety since the method circumvents the use of highly lachrymatric α-bromoketones as starting materials, high product yields (up to 98%), short reaction times, reusable solid Brønsted acid catalyst (HClO4-SiO2), and products that do not require column chromatography purification are all attractive features of this FCDR strategy. Electrochemical properties of THIs (6) are examined by cyclic voltammetry. The HOMO and LUMO energy level of THIs, 6a, 6c, 6d, 6j, 6o-6v, 6y, and 6aa are comparable with the reported ambipolar materials, and the HOMO levels of other THIs, 6b, 6e-6i, 6n, 6w, 6x, 6z and 6 ab-6ae are similar with the most commonly used hole transporting materials (HTMs).

Organocatalytic Enantioselective α-Bromination of Aldehydes with N-Bromosuccinimide.

Despite the wealth of existing organocatalytic, enantioselective transformations, the α-bromination of aldehydes remains a challenging reaction. The four examples reported to date require expensive, inconvenient brominating agents to achieve the desired products in excellent yields and enantioselectivities. The preferred brominating agent, N-bromosuccinimide (NBS), has been repeatedly discarded for these reactions because it results in low yields and relatively poor enantioselectivities. We describe a methodology that uses NBS and performs excellently with low catalyst loadings, short reaction times, and mild temperatures.

Utilization of N-bromosuccinimide for the sensitive spectrophotometric determination of pipazethate HCl as antitussive drug in pure and dosage forms.

OBJECTIVES: Three simple, sensitive, precise, reproducible and validated spectrophotometric methods have been developed for the quantification of pipazethate HCl as antitussive drug in pure and dosage forms. METHODS: The methods are based on utilization of N-bromosuccinimide as an oxidant and three dyes, amaranth, methylene blue, and indigo carmine, as auxiliary reagents. The proposed methods are based on oxidation reaction of pipazethate HCl with a known excess of N-bromosuccinimide in acid medium, followed by determination of unreacted N-bromosuccinimide by the reaction with a fixed amount of dyes, amaranth, methylene blue, and indigo carmine followed by the measurement of the absorbance at 520, 663 and 610nm, respectively. The optimization of the reaction conditions was investigated. RESULTS: Under the optimum conditions, linear relationships with good correlation coefficients (0.9998-0.9999) were found over the concentration ranges of 0.3-9.0, 0.5-12 and 0.5-10µgmL-1 with a limit of detection (LOD) of 0.1, 0.15 and 0.15µgmL-1 using amaranth, methylene blue, and indigo carmine methods, respectively. Intra-day and inter-day accuracy and precision of the methods have been evaluated. No interference was observed from the common tablet excipients. CONCLUSION: The developed methods were validated in accordance with ICH guidelines and successfully applied to the analysis of pipazethate HCl in dosage forms with good accuracy and precision. The reliability of the methods was further ascertained by performing recovery studies via the standard addition method. Statistical comparison of the results obtained by applying the proposed methods with those of the reported method by applying Student's t-test and variance ratio F-test at the 95% confidence level revealed good agreement and indicates no significant difference in accuracy and precision.

Dibrominative Spirocyclization of 2-Butynolyl Anilides: Synthesis of gem-Dibromospirocyclic Benzo[d][1,3]oxazines and Their Application in the Synthesis of 4H-Furo[3,2-b]indoles.

The combination of catalytic aqueous hydrochloric acid (HCl) and N-bromosuccinimide (NBS) generated electrophilic bromine monochloride (BrCl), which readily induced spiroannulation of 2-alkynolyl anilides (n = 1-3) to form gem-dibromospirocyclic benzo[d][1,3]oxazines in up to 92% yield. The reaction occurred under mild and metal-free conditions using EtOAc as a green solvent. The resulted spirocyclic products contained benzo[d][1,3]oxazine, which was useful both as a pharmacophore and synthetic precursor. In addition, the current protocol allowed to effortlessly introduce the sp3-gem-dibromide carbon adjacent to the sterically demanding spiroketal center. These spiroheterocycles (n = 1) were shown to be synthetically versatile and conveniently maneuvered. Base-promoted debrominative aromatization of these spirocycles unmasked rare and synthetically useful 2-aryl-3-bromofurans in mostly excellent yields. These 3-bromofurans were well-suited substrates for intramolecular Ullmann C-N bond coupling to construct difficult-to-prepare 4H-furo[3,2-b]indoles. Additionally, the current protocol was flexible and adaptable to preparing the gem-dichloride variants.

Radical Monofluoroalkylative Alkynylation of Olefins by a Docking-Migration Strategy.

A radical-mediated monofluoroalkylative alkynylation of alkenes is disclosed for the first time. The reaction demonstrates a remarkably broad substrate scope in which both activated and unactivated alkenes are suitable starting materials. The concurrent addition of an alkynyl and a monofluoroalkyl group onto an alkene proceeds through a docking-migration sequence, affording a vast array of valuable fluoroalkyl-substituted alkynes. Many complex natural products and drug derivatives are readily functionalized, demonstrating that this method can be used for late-stage alkynylation.

One-Pot NBS-Promoted Synthesis of Imidazoles and Thiazoles from Ethylarenes in Water.

A facile and eco-friendly method has been developed for the synthesis of imidazoles and thiazoles from ethylarenes in water. The reaction proceeds via in situ formation of α-bromoketone using NBS as a bromine source as well as an oxidant, followed by trapping with suitable nucleophiles to provide the corresponding products in good yields under metal-free conditions.

Carbon dots-involved chemiluminescence: Recent advances and developments.

In recent years, more and more nanomaterials-based chemiluminescence (CL) systems have appeared to improve the sensitivity and expand the scope of the analytical applications with the explosive growth and development of nanomaterials and technology. As a fascinating class of luminescent carbon nanomaterials, carbon dots (CDs) are now substantially studied in fabricating CL based assays due to their unique optical and mechanical properties. Herein, we summarize and highlight the current developments of CDs-involved weak or ultraweak CL systems, as well as the corresponding mechanisms and proper applications in some fields. CDs can take part in the CL reactions as oxidants, emitting species directly involved in redox oxidation, energy acceptors of CL energy transfer, or even catalysts involving other luminophores. In fact, they always have more than one role in many cases, owing to the formation of various excited species with short life in CL systems. Therefore, in this review article, the most recent progress of the different CDs-assisted CL systems including the mechanisms and applications are presented. Finally, the conclusions and future prospects of this field are also discussed. The significant features of the CDs-based CL systems may open up new prospects and challenges in a wider range of fields.

Hydrolysis of oligosaccharides by a fungal α-galactosidase from fruiting bodies of a wild mushroom Leucopaxillus tricolor.

A novel acidic α-galactosidase (EC 3.2.1.22) designated as Leucopaxillus tricolor α-galactosidase (LTG) has been purified to homogeneity from the fruiting bodies of L. tricolor to 855-fold with a specific activity of 956 U mg-1 by the application of chromatography and gel filtration. The molecular mass of LTG was estimated to be 60 kDa as determined by both SDS-PAGE and by gel filtration. The purified enzyme was identified by LC-MS/MS and four inner amino acid sequences were obtained. When 4-nitrophenyl α-D-glucopyranoside (pNPGal) was used as substrate, the optimal pH and optimal temperature of LTG were pH 5.0 and 50 °C, respectively. The enzyme activity was strongly inhibited by Hg2+ , Fe3 , Cu2+ , Cd2+ , and Mn2+ ions. The chemical modification agent N-bromosuccinimide (NBS) completely inhibited the enzyme activity of LTG, indicating the paramount importance of tryptophan residue(s) to its enzymatic activity. Besides, LTG displayed wide substrate diversity with activity toward a variety of substrates such as stachyose, raffinose, melibiose, locust bean gum, and guar gum. Given the good ability of degrading the non-digestible and flatulence-causing oligosaccharides, this fungus may become a useful source of α-galactosidase for multiple applications.

Esterification of Aryl/Alkyl Acids Catalysed by N-bromosuccinimide under Mild Reaction Conditions.

N-halosuccinimides (NXSs) are well-known to be convenient, easily manipulable and low-priced halogenation reagents in organic synthesis. In the present work, N-bromosuccinimide (NBS) has been promoted as the most efficient and selective catalyst among the NXSs in the reaction of direct esterification of aryl and alkyl carboxylic acids. Comprehensive esterification of substituted benzoic acids, mono-, di- and tri-carboxy alkyl derivatives has been performed under neat reaction conditions. The method is metal-free, air- and moisture-tolerant, allowing for a simple synthetic and isolation procedure as well as the large-scale synthesis of aromatic and alkyl esters with yields up to 100%. Protocol for the recycling of the catalyst has been proposed.

Characterization of an acidic α-galactosidase from hemp (Cannabis sativa L.) seeds and its application in removal of raffinose family oligosaccharides (RFOs).

An acidic α-galactosidase designated as hemp seed α-galactosidase (HSG) was purified from hemp (Cannabis sativa L.) seeds. By means of chromatographic procedures which involved chromatography on the cation-exchangers CM-cellulose and SP-Sepharose, chromatography on the anion-exchangers DEAE-cellulose and Q-Sepharose, and gel filtration on Superdex 75 using fast protein liquid chromatography, HSG was purified to electrophoretic homogeneity. Results of SDS-PAGE and gel filtration on FPLC Superdex 75 revealed that the enzyme was a monomeric protein with a molecular weight of 38 kDa. Sequences of the inner peptides of the α-galactosidase obtained by MALDI-TOF-MS showed that HSG was a novel α-galactosidase since there was a little similarity to the majority of α-galactosidases recorded in the literature. A pH of 3.0 and a temperature of 50°C were optimal for the activity of the enzyme. The activity of HSG was inhibited by the chemical modification with N-bromosuccinimide (NBS) reagent. HSG contained 16 tryptophan residues and two tryptophan residues on the surface, which were crucial to the α-galactosidase activity. The heavy metal ions Cd2+, Cu2+, Hg2+ and Zn2+ inhibited its activity. The Km and Vmax for the hydrolysis of pNPGal (4-nitrophenyl α-D-galactopyranoside) were respectively 0.008 mM and 68 µM min-1 mg-1. HSG also catalyzed the hydrolysis of raffinose and other natural substrates. Hence the α-galactosidase possesses a tremendous potential for food and feed industries in the elimination of indigestible oligosaccharides from leguminous products.

Determination of urea in milk based on N-bromosuccinimide-dichlorofluorescein postchemiluminescence method.

A new postchemiluminescence (PCL) reaction was observed when urea was injected into the reaction mixture after the CL reaction of N-bromosuccinimide and dichlorofluorescein. A possible reaction mechanism was proposed based on the studies of the CL kinetic characteristics, CL spectra, fluorescence spectra, and other experiments. A new flow injection CL method for the determination of urea was established based on the PCL reaction. The relative standard deviation for the determination of urea was 1.3% (n = 11, c = 5.0 × 10-8 g/mL). The CL intensity responded linearly to the concentration of urea in the range 2.0 × 10-9-1.0 × 10-6 g/mL (r = 0.9992). The detection limit was 7 × 10-10 g/mL. The method had been applied to the determination of urea in milk with satisfactory results.

Purification and Properties of Extracellular Lipases with Transesterification Activity and 1,3-Regioselectivity from Rhizomucor miehei and Rhizopus oryzae.

Rhizomucor miehei NRRL 5282 and Rhizopus oryzae NRRL 1526 can produce lipases with high synthetic activities in wheat bran-based solid-state culture. In this study, the purification and biochemical characterization of the lipolytic activities of these lipases are presented. SDS-PAGE indicated a molecular mass of about 55 and 35 kDa for the purified R. miehei and Rh. oryzae enzymes, respectively. p-Nitrophenyl palmitate (pNPP) hydrolysis was maximal at 40°C and pH 7.0 for the R. miehei lipase, and at 30°C and pH 5.2 for the Rh. oryzae enzyme. The enzymes showed almost equal affinity to pNPP, but the Vmax of the Rh. oryzae lipase was about 1.13 times higher than that determined for R. miehei using the same substrate. For both enzymes, a dramatic loss of activity was observed in the presence of 5 mM Hg2+, Zn2+, or Mn2+, 10 mM N-bromosuccinimide or sodium dodecyl sulfate, and 5-10% (v/v) of hexanol or butanol. At the same time, they proved to be extraordinarily stable in the presence of n-hexane, cyclohexane, n-heptane, and isooctane. Moreover, isopentanol up to 10% (v/v) and propionic acid in 1 mM concentrations increased the pNPP hydrolyzing activity of R. miehei lipase. Both enzymes had 1,3-regioselectivity, and efficiently hydrolyzed p-nitrophenyl (pNP) esters with C8-C16 acids, exhibiting maximum activity towards pNP-caprylate (R. miehei) and pNP-dodecanoate (Rh. oryzae). The purified lipases are promising candidates for various biotechnological applications.

Selective and Efficient Generation of ortho-Brominated para-Substituted Phenols in ACS-Grade Methanol.

The mono ortho-bromination of phenolic building blocks by NBS has been achieved in short reaction times (15-20 min) using ACS-grade methanol as a solvent. The reactions can be conducted on phenol, naphthol and biphenol substrates, giving yields of >86% on gram scale. Excellent selectivity for the desired mono ortho-brominated products is achieved in the presence of 10 mol % para-TsOH, and the reaction is shown to be tolerant of a range of substituents, including CH3, F, and NHBoc.

Regioselective Oxo-Amination of Alkenes and Enol Ethers with N-Bromosuccinimide-Dimethyl Sulfoxide Combination: A Facile Synthesis of α-Amino-Ketones and Esters.

An unprecedented conversion of alkenes and enol ethers to the corresponding α-imido carbonyl compounds with excellent regioselectivity and yields has been developed. This oxo-amination process employs readily available N-bromosuccinimide (NBS) and secondary amines as N-sources and dimethyl sulfoxide (DMSO) as the oxidant and also leads to the production of amino alcohols in a single step on reduction, thus broadening the scope of this operationally simple reaction. For the first time, the formation of reactive Me2S(+)-O-Br species generated by the interaction of NBS with DMSO has been proven.

Preparation and characterization of a novel variant of human tumor necrosis factor-related apoptosis-inducing ligand from the rhesus monkey, Macaca mulatta.

Human tumor necrosis factor-related apoptosis-inducing ligand (hTRAIL) and its variants are attractive antitumor drug candidates. The predicted amino acid sequence of the functional extracellular domain of Macaca mulatta TRAIL (mmTRAIL) was found to differ from that of hTRAIL at four positions. In this study, the gene encoding mmTRAIL was cloned and recombinantly expressed in Escherichia coli at a yield of approximately 20-30 mg/L, which was two times higher than that of hTRAIL. SDS-PAGE showed that denatured mmTRAIL and hTRAIL had similar molecular weights. However, size-exclusion chromatography and dynamic light scattering (DLS) analysis demonstrated that the molecular size of native mmTRAIL was smaller than that of native hTRAIL. Cooling solutions of these proteins from room temperature to 0 °C induced considerable precipitation of hTRAIL but not of mmTRAIL, indicating that mmTRAIL was more soluble than hTRAIL at low temperatures. Additionally, mmTRAIL was more resistant than hTRAIL to N-bromosuccinimide (NBS)-induced precipitation. Although mmTRAIL and hTRAIL showed comparable nanomolar affinities for human death receptors, the dissociation rate of the mmTRAIL-receptor complex was slower than that of the hTRAIL-receptor complex, suggesting that the mmTRAIL-receptor complex was more stable. Moreover, mmTRAIL induced caspase-dependent apoptosis in human tumor cells with an IC50 that was two to three times lower than that of hTRAIL. However, in vivo evaluation demonstrated that mmTRAIL or hTRAIL led to a similar level of tumor suppression in mice bearing COLO205 xenografts. Nevertheless, the advantage of its better solubility should promote the production and further use of mmTRAIL in cancer biotherapy.

Characterization of a Kunitz-type serine protease inhibitor from Solanum tuberosum having lectin activity.

Plant lectins and protease inhibitors constitute a class of proteins which plays a crucial role in plant defense. In our continuing investigations on lectins from plants, we have isolated, purified and characterized a protein of about 20 kDa, named PotHg, showing hemagglutination activity from tubers of Indian potato, Solanum tuberosum. De novo sequencing and MS/MS analysis confirmed that the purified protein was a Kunitz-type serine protease inhibitor having two chains (15 kDa and 5 kDa). SDS and native PAGE analysis showed that the protein was glycosylated and was a heterodimer of about 15 and 5 kDa subunits. PotHg agglutinated rabbit erythrocytes with specific activity of 640 H.U./mg which was inhibited by complex sugars like fetuin. PotHg retained hemagglutination activity over a pH range 4-9 and up to 80°C. Mannose and galactose interacted with the PotHg with a dissociation constant (Kd) of 1.5×10(-3) M and 2.8×10(-3) M, respectively as determined through fluorescence studies. Fluorescence studies suggested the involvement of a tryptophan in sugar binding which was further confirmed through modification of tryptophan residues using N-bromosuccinimide. Circular dichroism (CD) studies showed that PotHg contains mostly ß sheets (∼45%) and loops which is in line with previously characterized protease inhibitors and modeling studies. There are previous reports of Kunitz-type protease inhibitors showing lectin like activity from Peltophorum dubium and Labramia bojeri. This is the first report of a Kunitz-type protease inhibitor showing lectin like activity from a major crop plant and this makes PotHg an interesting candidate for further investigation.