Selective detection of azelnidipine in pharmaceuticals via carbon dot mediated spectrofluorimetric method: A green approach.

A spectrofluorimetric method using fluorescent carbon dots (CDs) was developed for the selective detection of azelnidipine (AZEL) pharmaceutical in the presence of other drugs. In this study, N-doped CDs (N-CDs) were synthesized through a single-step hydrothermal process, using citric acid and urea as precursor materials. The prepared N-CDs showed a highly intense blue fluorescence emission at 447 nm, with a photoluminescence quantum yield of ~21.15% and a fluorescence lifetime of 0.47 ns. The N-CDs showed selective fluorescence quenching in the presence of all three antihypertensive drugs, which was used as a successful detection platform for the analysis of AZEL. The photophysical properties, UV-vis light absorbance, fluorescence emission, and lifetime measurements support the interaction between N-CDs and AZEL, leading to fluorescence quenching of N-CDs as a result of ground-state complex formation followed by a static fluorescence quenching phenomenon. The detection platform showed linearity in the range 10-200 µg/ml (R2 = 0.9837). The developed method was effectively utilized for the quantitative analysis of AZEL in commercially available pharmaceutical tablets, yielding results that closely align with those obtained from the standard method (UV spectroscopy). With a score of 0.76 on the 'Analytical GREEnness (AGREE)' scale, the developed analytical method, incorporating 12 distinct green analytical chemistry components, stands out as an important technique for estimating AZEL.

Epoxide Ring-Opening Reactions for Abundant Production of Mugineic Acids and Nicotianamine Probes.

A succinct synthetic approach to mugineic acids and 2'-hydroxynicotianamine was established. Unlike all other synthetic methods, this approach utilized epoxide ring-opening reactions to form two C-N bonds and is characterized by the absence of redox reactions. Mugineic acid was synthesized from three readily available fragments on a gram scale in 6 steps. The protected 2'-hydroxynicotianamine was also synthesized in 4 steps, and the dansyl group, serving as a fluorophore, was introduced through a click reaction after propargylation of the 2'-hydroxy group. The dansyl-labeled nicotianamine (NA) iron complexes were internalized by oocytes overexpressing ZmYS1 (from maize) or PAT1 (from human) transporters, indicating successful transport of the synthesized NA-probe through these transporters.

Total synthesis of [13 C2 ]-labeled phytosiderophores of the mugineic and avenic acid families.

We, herein, report the synthesis of 13 C2 -labeled natural products from the mugineic acid and avenic acid family. These phytosiderophores ("plant iron carriers") are built up from non-proteinogenic amino acids and play a key role in micronutrient uptake in gramineous plants. In this work, two central building blocks are prepared from labeled starting materials (13 C2 -bromoacetic acid, 13 C2 -glycine) and further employed in our recently reported divergent, branched synthetic strategy delivering eight isotopically labeled phytosiderophores. The required labeled building blocks (13 C2 -l-allylglycine and a related hydroxylated derivative) were prepared via enantioselective phase-transfer catalysis and enantio- and diastereoselective aldol condensation with a chiral auxiliary, respectively, both potentially valuable themselves for other synthetic routes toward labeled (natural) products.

L-Proline Prevents Endoplasmic Reticulum Stress in Microglial Cells Exposed to L-azetidine-2-carboxylic Acid.

L-Azetidine-2-carboxylic acid (AZE) is a non-protein amino acid that shares structural similarities with its proteogenic L-proline amino acid counterpart. For this reason, AZE can be misincorporated in place of L-proline, contributing to AZE toxicity. In previous work, we have shown that AZE induces both polarization and apoptosis in BV2 microglial cells. However, it is still unknown if these detrimental effects involve endoplasmic reticulum (ER) stress and whether L-proline co-administration prevents AZE-induced damage to microglia. Here, we investigated the gene expression of ER stress markers in BV2 microglial cells treated with AZE alone (1000 µM), or co-treated with L-proline (50 µM), for 6 or 24 h. AZE reduced cell viability, nitric oxide (NO) secretion and caused a robust activation of the unfolded protein response (UPR) genes (ATF4, ATF6, ERN1, PERK, XBP1, DDIT3, GADD34). These results were confirmed by immunofluorescence in BV2 and primary microglial cultures. AZE also altered the expression of microglial M1 phenotypic markers (increased IL-6, decreased CD206 and TREM2 expression). These effects were almost completely prevented upon L-proline co-administration. Finally, triple/quadrupole mass spectrometry demonstrated a robust increase in AZE-bound proteins after AZE treatment, which was reduced by 84% upon L-proline co-supplementation. This study identified ER stress as a pathogenic mechanism for AZE-induced microglial activation and death, which is reversed by co-administration of L-proline.

Crystal structure analysis of N-acetylated proline and ring size analogs.

Crystal structures of N-acetylated proline and homologs with four- and six-membered rings (azetidine carboxylic acid and piperidine carboxylic acid) were obtained and compared. The distinctly different conformations of the four-, five-, and six-membered rings reflect Bayer strain, n → π* interaction, and allylic strain, and result in crystal lattices with a zigzag structure.

Azetidine-2-Carboxylic Acid-Induced Oligodendrogliopathy: Relevance to the Pathogenesis of Multiple Sclerosis.

The naturally occurring imino acid azetidine-2-carboxylic acid (Aze) is consumed by humans and can be misincorporated in place of proline in myelin basic protein (MBP) in vitro. To determine Aze effects on the mammalian CNS in vivo, adult CD1 mice were given Aze orally or intraperitoneally. Clinical signs reminiscent of MBP-mutant mice occurred with 600 mg/kg Aze exposure. Aze induced oligodendrocyte (OL) nucleomegaly and nucleoplasm clearing, dilated endoplasmic reticulum, cytoplasmic vacuolation, abnormal mitochondria, and Aze dose-dependent apoptosis. Immunohistochemistry demonstrated myelin blistering and nuclear translocation of unfolded protein response (UPR)/proinflammatory molecules (ATF3, ATF4, ATF6, eIF2α, GADD153, NFκB, PERK, XBP1), MHC I expression, and MBP cytoplasmic aggregation in OL. There were scattered microglial nodules in CNS white matter (WM); other CNS cells appeared unaffected. Mice given Aze in utero and postnatally showed more marked effects than their dams. These OL, myelin, and microglial alterations are found in normal-appearing WM (NAWM) in multiple sclerosis (MS) patients. Thus, Aze induces a distinct oligodendrogliopathy in mice that recapitulates MS NAWM pathology without leukocyte infiltration. Because myelin proteins are relatively stable throughout life, we hypothesize that Aze misincorporation in myelin proteins during myelinogenesis in humans results in a progressive UPR that may be a primary process in MS pathogenesis.

Theoretical studies on the coordination chemistry of phytosiderophores with special reference to Fe-nicotianamine complexes in graminaceous plants.

Nicotianamine (NA) is one of the metal-chelating molecules found in higher plants in abundance. Synthesized by the enzyme nicotianamine synthase, NA has a major role in the transport of iron in plant tissues. This research paper deals with the coordination chemistry of the possible complexes of NA, [FeII (NA)]-, and [FeIII (NA)] in detail, from a theoretical standpoint. The chemical computations on the [FeII (NA)]- and [FeIII (NA)] complexes show that NA can bind with both Fe (+ 2) and Fe (+ 3) ions. The calculations confirm that the [FeIII (NA)] is thermodynamically more stable in comparison with [FeII (NA)]-, while [FeII (NA)]- is kinetically more stable than [FeIII (NA)]. Under the physiological conditions prevailing in plant tissues, [FeIII (NA)] can undergo reduction, but the auto-oxidation of [FeII (NA)]- to [FeIII (NA)] is prevented. In summary, NA can translocate Fe ions within plant tissues, wherever required, both as Fe (+ 2) and Fe (+ 3) complexes.

A highly conserved mechanism for the detoxification and assimilation of the toxic phytoproduct L-azetidine-2-carboxylic acid in Aspergillus nidulans.

Plants produce toxic secondary metabolites as defense mechanisms against phytopathogenic microorganisms and predators. L-azetidine-2-carboxylic acid (AZC), a toxic proline analogue produced by members of the Liliaceae and Agavaciae families, is part of such a mechanism. AZC causes a broad range of toxic, inflammatory and degenerative abnormalities in human and animal cells, while it is known that some microorganisms have evolved specialized strategies for AZC resistance. However, the mechanisms underlying these processes are poorly understood. Here, we identify a widespread mechanism for AZC resistance in fungi. We show that the filamentous ascomycete Aspergillus nidulans is able to not only resist AZC toxicity but also utilize it as a nitrogen source via GABA catabolism and the action of the AzhA hydrolase, a member of a large superfamily of detoxifying enzymes, the haloacid dehalogenase-like hydrolase (HAD) superfamily. This detoxification process is further assisted by the NgnA acetyltransferase, orthologue of Mpr1 of Saccharomyces cerevisiae. We additionally show that heterologous expression of AzhA protein can complement the AZC sensitivity of S. cerevisiae. Furthermore, a detailed phylogenetic analysis of AzhA homologues in Fungi, Archaea and Bacteria is provided. Overall, our results unravel a widespread mechanism for AZC resistance among microorganisms, including important human and plant pathogens.

Development of a mugineic acid family phytosiderophore analog as an iron fertilizer.

Iron (Fe) is an essential nutrient, but is poorly bioavailable because of its low solubility in alkaline soils; this leads to reduced agricultural productivity. To overcome this problem, we first showed that the soil application of synthetic 2'-deoxymugineic acid, a natural phytosiderophore from the Poaceae, can recover Fe deficiency in rice grown in calcareous soil. However, the high cost and poor stability of synthetic 2'-deoxymugineic acid preclude its agricultural use. In this work, we develop a more stable and less expensive analog, proline-2'-deoxymugineic acid, and demonstrate its practical synthesis and transport of its Fe-chelated form across the plasma membrane by Fe(III)•2'-deoxymugineic acid transporters. Possibility of its use as an iron fertilizer on alkaline soils is supported by promotion of rice growth in a calcareous soil by soil application of metal free proline-2'-deoxymugineic acid.

A Unified Approach to Phytosiderophore Natural Products.

This work reports on the concise total synthesis of eight natural products of the mugineic acid and avenic acid families (phytosiderophores). An innovative "east-to-west" assembly of the trimeric products resulted in a high degree of divergence enabling the formation of the final products in just 10 or 11 steps each with a minimum of overall synthetic effort. Chiral pool starting materials (l-malic acid, threonines) were employed for the outer building blocks while the middle building blocks were accessed by diastereo- and enantioselective methods. A highlight of this work consists in the straightforward preparation of epimeric hydroxyazetidine amino acids, useful building blocks on their own, enabling the first synthesis of 3''-hydroxymugineic acid and 3''-hydroxy-2'-deoxymugineic acid.

Speciation of essential nutrient trace elements in coconut water.

Coconut water (Cocos Nucifera) is shown to be a source of essential elements present in the form of low-molecular weight stable complexes known for their bio-availability. The total element concentrations were in the range of 0.2-2.7, 0.3-1, 3-14 and 0.5-2 ppm for Fe, Cu, Mn, and Zn, respectively, and varied as a function of the origin of the nut and its maturity. Speciation was investigated by size-exclusion chromatography - inductively coupled plasma mass spectrometry (ICPMS), and hydrophilic interaction liquid chromatography (HILIC) - electrospray-OrbitrapMS. The metal species identified included: iron complexes with citrate and malate: FeIII(Cit)3(Mal), FeIII(Cit)2(Mal)2, FeIII(Mal)2, glutamine: FeIII(Glu)2 and nicotianamine: FeII(NA); copper complexes with phenylanine: CuII(Phe)2 and CuII(Phe)3 and nicotianamine: CuII(NA); zinc complexes with citrate: ZnII(Cit)2 and nicotianamine ZnII(NA) and manganese complex with asparagine MnII(Asp)2. The contributions of the individual species to the total elements concentrations could be estimated by HILIC - ICP MS.

Nicotianamine-chelated iron positively affects iron status, intestinal morphology and microbial populations in vivo (Gallus gallus).

Wheat flour iron (Fe) fortification is mandatory in 75 countries worldwide yet many Fe fortificants, such as Fe-ethylenediaminetetraacetate (EDTA), result in unwanted sensory properties and/or gastrointestinal dysfunction and dysbiosis. Nicotianamine (NA) is a natural chelator of Fe, zinc (Zn) and other metals in higher plants and NA-chelated Fe is highly bioavailable in vitro. In graminaceous plants NA serves as the biosynthetic precursor to 2' -deoxymugineic acid (DMA), a related Fe chelator and enhancer of Fe bioavailability, and increased NA/DMA biosynthesis has proved an effective Fe biofortification strategy in several cereal crops. Here we utilized the chicken (Gallus gallus) model to investigate impacts of NA-chelated Fe on Fe status and gastrointestinal health when delivered to chickens through intraamniotic administration (short-term exposure) or over a period of six weeks as part of a biofortified wheat diet containing increased NA, Fe, Zn and DMA (long-term exposure). Striking similarities in host Fe status, intestinal functionality and gut microbiome were observed between the short-term and long-term treatments, suggesting that the effects were largely if not entirely due to consumption of NA-chelated Fe. These results provide strong support for wheat with increased NA-chelated Fe as an effective biofortification strategy and uncover novel impacts of NA-chelated Fe on gastrointestinal health and functionality.

Chronological Delivery of Antihypertensive Drugs in Bilayered Core-in-Cup Buccoadhesive Tablets: In Vitro and In Vivo Evaluation.

Hypertension shows circadian blood pressure rhythms (day-night pattern) that urge the delivery of antihypertensive drugs at the right time in the desired levels. Thus, a bilayered core-in-cup buccoadhesive tablet was formulated that immediately releases olmesartan, to give a burst effect, and controls azelnidipine release, to prolong its therapeutic effect. The main challenge was the poor bioavailability of azelnidipine due to its poor aqueous solubility and first-pass effect. Hence, liquisolid compact buccoadhesive tablets were prepared to enhance solubility, dissolution profiles, and bypass the oral route. Two factorial designs were conducted to study the type and concentration effect of the mucoadhesive polymers on the dissolution and mucoadhesion of olmesartan and azelnidipine. Characterization studies were conducted regarding drug content, surface pH, water uptake, mucoadhesive strength, in vitro release, and ex vivo permeability. The core-in-cup olmesartan/azelnidipine buccoadhesive tablet showed similar release profile to the statistically optimized formulae of each drug. In vitro dissolution study showed enhanced release of azelnidipine than the directly compressed tablets, to comply with the regulatory standards of controlled release systems. In vivo pharmacokinetic study of olmesartan and azelnidipine conducted on human volunteers against Rezaltas® 10/8 mg tablet showed percentage relative bioavailability of 106.12 and 470.82%, respectively. Graphical Abstract.

Improved bioavailability of Azelnidipine gastro retentive tablets-optimization and in-vivo assessment.

Azelnidipine, dihydropyridine based calcium channel blocker has been used for treating ischemic heart disease and cardiac remodeling after myocardial infarction but it is having a low bioavailability due to its poor solubility. The present study is to investigate the formulation and evaluation of floating tablets of Azelnidipine for controlled release and to increase bioavailability by increasing the gastrointestinal transit time and mucoadhesion of drug. The gastro retentive tablets were prepared by direct compression method using different concentrations of combination of Polyoxyethylene oxide WSR 303 as hydrophilic polymer and Potassium bicarbonate as gas generating agent. Main effects of the formulation variables were evaluated quantitatively using design approach showing that both independent variables have significant effects on floating lag time, % drug release at 1 h (D1 h) and time required to release 90% of the drug (t90). The statistically optimized formulation (F3) released 95.11 ±â€¯1.43% drug for 12 h followed K-Peppas drug release kinetics indicating release of drug by diffusion and erosion mechanism. Evaluation of the optimized formulation in vivo in human volunteers showed that the GFT was buoyant in gastric fluid and that its gastric residence time was enhanced. Pharmacokinetics studies carried out revealed significant (P < 0.05) equivalent Cmax, longer Tmax and higher AUC values for the optimized formula compared to the marketed oral product. From the results obtained it can be concluded that Azelnidipine Gastro retentive tablets with enhanced bioavailability and better release pattern is suitable for more effective treatment compared to marketed conventional tablets.

Core-in-cup/liquisol dual tackling effect on azelnidipine buccoadhesive tablet micromeritics, in vitro release, and mucoadhesive strength.

Reduced bioavailability of azelnidipine is related to its poor aqueous solubility and extensive first-pass metabolism, which hinder its efficacy. These problems were addressed by implementing (1) a liquisol technique for promoting the dissolution rate in a controlled-release manner and (2) a core-in-cup bucco-adhesive drug delivery system as an alternative to the oral route. A 33 factorial design was used to study the effects of polymer type (sodium carboxymethyl cellulose (CMC Na), chitosan, or Carbomer P940) concentration (5, 10 or 15 %) and preparation technique (simple mix, liquisol or wet granulation) on the dissolution and mucoadhesion of core-in-cup azelnidipine buccoadhesive tablets. Tablet micromeritics, swelling index, mucoadhesive strength and in vitro release were characterized. Statistical analyses of these factors show ed significant effects on the studied responses, where F#16 prepared by the liquisol technique and containing 15 % CMC Na was chosen with an overall desirability of 0.953.

Inhibitory effects of antihypertensive drugs on human cytochrome P450 2J2 activity: Potent inhibition by azelnidipine and manidipine.

The inhibitory effects of antihypertensive drugs (dihydropyridine calcium channel blockers, angiotensin II receptor blockers, and angiotensin-converting enzyme inhibitors) on cytochrome P450 2J2 (CYP2J2) activity were examined. Amlodipine, azelnidipine, barnidipine, benidipine, cilnidipine, efonidipine, felodipine, manidipine, nicardipine, nifedipine, nilvadipine, nisoldipine, nitrendipine, telmisartan, delapril, and quinapril inhibited luciferin-2J2/4F12 O-dealkylase activity of recombinant human CYP2J2 in a concentration-dependent manner (IC50 = 0.116-9.19 µM). Kinetic analyses of the inhibition indicated that azelnidipine, barnidipine, benidipine, cilnidipine, efonidipine, manidipine, nicardipine, telmisartan, delapril, and quinapril competitively inhibited CYP2J2 activity, while amlodipine, felodipine, nifedipine, nilvadipine, nisoldipine, and nitrendipine showed mixed inhibition. Among these drugs, manidipine showed the strongest reversible inhibition with Ki value of 0.0294 µM. The docking simulation data supported the potent inhibition of CYP2J2 by these drugs. Next, the effect of preincubation on CYP2J2 inhibition was investigated to determine whether these antihypertensive drugs inhibited CYP2J2 activity in a metabolism-dependent manner. A 20-min preincubation of azelnidipine and felodipine in the presence of NADPH potentiated the inhibition of CYP2J2. Furthermore, kinetic analysis of the inactivation showed that azelnidipine caused a preincubation time- and concentration-dependent decrease in CYP2J2 activity yielding kinact/KI value of 105 l/mmol/min, although felodipine showed no preincubation time-dependent inhibition. The azelnidipine-mediated inactivation required NADPH. These results indicated that manidipine is a potent competitive reversible inhibitor while azelnidipine is a potent mechanism-based inactivator of human CYP2J2.

Heterochiral Ala/(αMe)Aze sequential oligopeptides: Synthesis and conformational study.

α-Amino acid residues with a ϕ,ψ constrained conformation are known to significantly bias the peptide backbone 3D structure. An intriguing member of this class of compounds is (αMe)Aze, characterized by an Nα -alkylated four-membered ring and Cα -methylation. We have already reported that (S)-(αMe)Aze, when followed by (S)-Ala in the homochiral dipeptide sequential motif -(S)-(αMe)Aze-(S)-Ala-, tends to generate the unprecedented γ-bend ribbon conformation, as formation of a regular, fully intramolecularly H-bonded γ-helix is precluded, due to the occurrence of a tertiary amide bond every two residues. In this work, we have expanded this study to the preparation and 3D structural analysis of the heterochiral (S)-Ala/(R)-(αMe)Aze sequential peptides from dimer to hexamer. Our conformational results show that members of this series may fold in type-II ß-turns or in γ-turns depending on the experimental conditions.

Metabolic engineering of bread wheat improves grain iron concentration and bioavailability.

Bread wheat (Triticum aestivum L.) is cultivated on more land than any other crop and produces a fifth of the calories consumed by humans. Wheat endosperm is rich in starch yet contains low concentrations of dietary iron (Fe) and zinc (Zn). Biofortification is a micronutrient intervention aimed at increasing the density and bioavailability of essential vitamins and minerals in staple crops; Fe biofortification of wheat has proved challenging. In this study we employed constitutive expression (CE) of the rice (Oryza sativa L.) nicotianamine synthase 2 (OsNAS2) gene in bread wheat to up-regulate biosynthesis of two low molecular weight metal chelators - nicotianamine (NA) and 2'-deoxymugineic acid (DMA) - that play key roles in metal transport and nutrition. The CE-OsNAS2 plants accumulated higher concentrations of grain Fe, Zn, NA and DMA and synchrotron X-ray fluorescence microscopy (XFM) revealed enhanced localization of Fe and Zn in endosperm and crease tissues, respectively. Iron bioavailability was increased in white flour milled from field-grown CE-OsNAS2 grain and positively correlated with NA and DMA concentrations.

Syntheses and in vitro evaluation of new S1PR1 compounds and initial evaluation of a lead F-18 radiotracer in rodents.

Thirteen new sphingosine-1-phosphate receptor 1 (S1PR1) ligands were designed and synthesized by replacing azetidine-3-carboxylic acid moiety of compound 4 with new polar groups. The in vitro binding potency of these new analogs toward S1PR1 was determined. Out of 13 new compounds, four compounds 9a, 10c, 12b, and 16b displayed high S1PR1 binding potency with IC50 values of 13.2 ±â€¯3.2, 14.7 ±â€¯1.7, 9.7 ±â€¯1.6, and 6.3 ±â€¯1.3 nM, respectively; further binding studies of these four ligands toward S1PR2-5 suggested they are highly selective for S1PR1 over other S1PRs. The radiosynthesis of the lead radiotracer [18F]12b was achieved with good radiochemical yield (∼14.1%), high radiochemical purity (>98%), and good specific activity (∼54.1 GBq/µmol, decay corrected to the end of synthesis, EOS). Ex vivo autoradiography and initial biodistribution studies in rodents were performed, suggesting that [18F]12b was able to penetrate the blood-brain barrier (BBB) with high brain uptake (0.71% ID/g at 60 min post-injection) and no defluorination was observed. In vitro autoradiography study in brain slices of lipopolysaccharides (LPS)-induced neuroinflammation mice indicated that SEW2871, a specific S1PR1 ligand was able to reduce the uptake of [18F]12b, suggesting [18F]12b has S1PR1 specific binding. These initial results suggested that [18F]12b has potential to be an F-18 labeled radiotracer for imaging S1PR1 in the brain of the animal in vivo.

[Bioinorganic Chemistry of Iron].

　The X-ray crystallographic analysis of the single-crystal mugineic acid-Cu(II) complex showed that mugineic acid acts as a hexadentate ligand. Mugineic acid, a typical phytosiderophore, shows a marked stimulating effect on 59Fe-uptake and chlorophyll synthesis in rice plants. A salient feature is the higher reduction potential of the mugineic acid-Fe(III) complex than those of bacterial siderophores. X-ray diffraction study of the structurally analogous Co(III) complex of the mugineic acid-Fe(III) complex demonstrates that the azetidine nitrogen and secondary amine nitrogen, and both terminal carboxylate oxygens, coordinate as basal planar donors, and the hydroxyl oxygen and intermediate carboxylate oxygen bind as axial donors in a nearly octahedral configuration. The iron-transport mechanism in gramineous plants appears to involve the excretion of mugineic acid from the roots, which aids Fe(III)-solubilization and reduction of Fe(III) to Fe(II). Manganese peroxidase (MnP) is a component of the lignin degradation system of the basidiomycetous fungus, Phanerochaete chrysosporium. To elucidate the heme environment of this novel Mn(II)-dependent extracellular enzyme, we studied its ESR and resonance Raman spectroscopic properties. Consequently, it is most likely that the heme environment of MnP resembles that of cytochrome c peroxidase. In addition, degradation methods using basidiomycetous fungi or Fe3+-H2O2 mixed reagent were developed for dioxins and polychlorinated biphenyls. The complete amino acid sequences of respective [2Fe-2S] ferredoxins were determined and compared with those of other higher plants. Finally, the toxic effects of iron on human health and the development of novel antibacterial drugs capable of inhibiting the iron transport system of Vibrio vulnificus are described.