Development of an innovative turn-on fluorescent probe for targeted in-vivo detection of nitric oxide in rat brain extracts as a biomarker for migraine disease.

Nitric oxide (NO) is one of the reactive nitrogen species (RNS) that has been proposed to be a key signaling molecule in migraine. Migraine is a neurological disorder that is linked to irregular NO levels, which necessitates precise NO quantification for effective diagnosis and treatment. This work introduces a novel fluorescent probe, 2,3-diaminonaphthelene-1,4-dione (DAND), which was designed and synthesized to selectively detect NO in-vitro and in-vivo as a migraine biomarker. DAND boasts high aqueous solubility, biocompatibility, and facile synthesis, which enable highly selective and sensitive detection of NO under physiological conditions. NO reacts with diamine moieties (recognition sites) of DAND, results in the formation of a highly fluorescent product (DAND-NO) known as 1H-naphtho[2,3-d][1,2,3]triazole-4,9-dione at λem 450 nm. The fluorescence turn-on sensing mechanism operates through an intramolecular charge transfer (ICT) mechanism. To maximize fluorescence signal intensity, parameters including DAND concentration, reaction temperature, reaction time and pH were systematically optimized for sensitive and precise NO determination. The enhanced detection capability (LOD = 0.08 µmol L-1) and high selectivity of the probe make it a promising tool for NO detection in brain tissue homogenates. This demonstrates the potential diagnostic value of the probe for individuals suffering from migraine. Furthermore, this study sheds light on the potential role of zolmitriptan (ZOLM), an antimigraine medication, in modulating NO levels in the brain of rats with nitroglycerin-induced migraine, emphasizing its significant impact on reducing NO levels. The obtained results could have significant implications for understanding how ZOLM affects NO levels and may aid in the development of more targeted and effective migraine treatment strategies.

Utility of dansyl chloride for the establishment of a sensitive spectrofluorimetric approach for estimating midodrine hydrochloride: application to content uniformity testing.

A new, straightforward spectrofluorimetric approach with high sensitivity was established for determining midodrine hydrochloride based on derivatizing this drug through its reaction with 5-(dimethylamino)naphthalene-1-sulfonyl chloride (dansyl chloride). The highly fluorescent product was extracted with methylene chloride, and then its emission was measured at 532 nm after excitation at 339 nm. The reaction was conducted in aqueous medium containing 0.1 M borate buffer (pH 8.2). The results showed that the proposed method is sensitive with high linearity in the range from 0.1 to 3 µg mL-1. The lower limits of detection and quantitation were 29 and 88 ng mL-1, respectively. Furthermore, the proposed approach was analytically assessed by applying the ICH guidelines. The suggested approach was effectively utilized for the estimation of the medicine in its marketable tablet formulations with excellent recovery and without any interfering effect from excipients. Moreover, the presented approach was utilized to test the content uniformity of commercial tablets following the USP guidelines.

QuEChERS-assisted ion pair chromatography/fluorescence detection method for determination of antimigraine combination therapy in rabbit plasma samples: Application to a pharmacokinetic study.

Antimigraine combination therapy has shown significant effectiveness in relieving pain, as well as reducing the frequency, duration, and severity of migraine attacks if compared to a single migraine medication. This work represents the first analytical investigation for emphasizing the synergistic effect of combining ophthalmic beta blockers with triptans in migraine treatment. The presented study was conducted to investigate the pharmacokinetic profile of almotriptan (ALM), a serotonin (5-HT1B/1D) receptor agonist used to treat migraine, when coadministered with timolol (TIM) or verapamil (VER) which are considered as an adjuvant therapy in migraine prevention. Ion pair chromatography (IPC) with online fluorescence detection was applied to simultaneously detect and quantify the binary mixtures of ALM/TIM and ALM/VER in rabbit plasma samples. The separation was achieved using a Platinum C18 analytical column with a mobile phase composed of methanol: 35 mmol L-1 phosphate buffer solution containing 10 mmol L-1 SDS at pH = 6.8 (60:40 v/v). Several parameters were evaluated during the optimization of separation conditions including mobile phase composition, buffer concentration, buffer pH and concentration of ion pair reagent. A thorough investigation of the retention mechanism was performed, and the results showed that Coulomb forces were the main contributors to the overall retention mechanism, which may be hydrophobically assisted. QuEChERS extraction technique was utilized to extract the investigated drugs from plasma samples and a detailed study was carried out to optimize partition/extraction solvents, pH, extraction salts, sample volume and clean-up step. The method had a limit of detection and quantitation of 5.6 and 16.9 ng mL-1 for ALM in ALM/TIM mixture and 2.5 and 7.6 ng mL-1 for ALM in ALM/VER mixture, with an overall recovery not less than 95.22%. This newly proposed method offers a faster alternative to existing chromatographic methods for extraction and determination of ALM in binary mixtures with TIM or VER in rabbit plasma and provides a platform for studying pharmacokinetic parameters. The coadministration of either TIM or VER with ALM resulted in a notable rise in Cmax (maximum plasma concentration) and AUC (area under the plasma concentration-time curve) of ALM, implying possible alterations in the absorption and overall exposure of ALM.

Studying the kinetic of midodrine degradations using TLC stability approach: Application to dosage form and human plasma.

A simple, rapid and selective thin layer chromatographic method has been developed for estimation of the antihypotension drug, midodrine hydrochloride, in pure form, tablet, spiked plasma and artificially degraded samples. Separation was carried out using silica gel 60-F254 as a stationary and mobile phase consisting of methanol: methylene chloride: ammonia in ratio of 8:2:0.2. The detection was carried out at wavelength of 290 nm. The retardation factor was found to be 0.7 and 0.49 for midodrine and its main degradation product desglymidodrine. The method showed linearity for midodrine over a concentration range of 50-1500 ng/spot with good correlation and determination coefficient. The method was applied successfully for analysis of commercial tablets and oral drops with good recovery and without interference of excipients. The method also was applied for studying the stability of the cited drug under different stress conditions including acidic, alkaline, hydrolytic, oxidative and photo- degradations. Furthermore, the kinetic of acidic and alkaline degradations was investigated and the rate constants were found to be 0.620 and 0.074 K h-1 while half life time (t1/2) values were 1.12 and 9.32 h, respectively.

Development of a simple validated spectrofluorometric method for the assay of midodrine in tablets dosage form; Application to content uniformity testing.

A new sensitive spectrofluorimetric technique has been established for the estimation of midodrine hydrochloride. This method depends on the condensation reaction of ortho-phthalaldehyde with the primary aliphatic amine of midodrine in the presence of 2-mercapto-ethanol. The pH of the medium was adjusted to 9.0 using 0.1 M borate buffer. The fluorescence of the product was measured at wavelength of 451 nm after excitation at 334 nm. The method was rectilinear over a concentrations range of 0.1 to 1.5 µg mL-1. The lower detection and quantitation limits were 31 and 94 ng mL-1, respectively. The method was investigated following the guidelines of the International Council of Harmonization. Analysis of commercial tablet dosage form was carried out successfully by the current method with excellent recovery percentages and with no influence from coexisted pharmaceutical additives .This method was used to evaluate the uniformity of the contents of commercial tablets according to the United States Pharmacopoeia.

Orthophthaldehyde as a fluorescent probe for the feasible and sensitive assay of heptaminol: application to dosage forms and real human plasma.

The antihypotensive drug heptaminol was determined using a spectrofluorimetric method and ortho-phthaladehyde as a fluorescence probe. The drug was mixed with the reagent in the presence of 2-mercaptoethanol and the reaction was carried out in slightly alkaline aqueous solution containing 0.1 M sodium hydroxide. The resulting product exhibited high fluorescence activity that was measured at 451 nm after excitation at 334 nm. The linearity range of the method was 5-100 ng ml-1 with a lower detection limit of 1.8 ng ml-1 . The procedure was evaluated according to the International Council of Harmonization guidelines. The proposed method was applied to analyze the drug in pharmaceutical tablets and oral drops. In addition, the present study represents the first spectrofluorimetric method for the determination of the cited drug in real human plasma. The method provided high recovery percentages without any interference from coexisting pharmaceutical excipients or the components of human plasma.

Vortex-assisted dispersive solid phase microextraction using Fe3O4/FeOOH magnetic nanocomposites for high-performance thin-layer chromatographic determination of zolmitriptan in rabbit plasma samples.

In this work, a fast, versatile, and convenient dispersive solid-phase micro-extraction (DSPME) method is combined with a spectro-densitometric technique for the analysis of zolmitriptan (ZOLM) in biological fluids. Fe3O4/FeOOH magnetic nanocomposites (MNCs) were prepared by a co-precipitation method in aqueous solutions and utilized subsequently as a sorbent in DSPME. By coupling DSPME with high-performance thin-layer chromatography (HPTLC) with fluorescence detection, the preconcentration and determination of (ZOLM) in presence of metoclopramide (MET) and paracetamol (PARA), which are prescribed as an adjuvant therapy with ZOLM, was accomplished. Adsorption capability was assessed using both Langmuir and Freundlich adsorption isotherm models. The adsorption data was fitted to Langmuir adsorption isotherm model as reflected by high determination coefficient (R2 = 0.9944). Moreover, adsorption kinetics was assessed by pseudo-first and pseudo-second order kinetic models. The data was fitted to pseudo-second order kinetics, which proves that ZOLM interaction with the adsorbent is a chemisorption process. Surface complexation with MNCs was suggested to explain the pH dependence of ZOLM sorption. The key parameters of extraction and desorption steps (including pH, extraction time, sample volume, magnetic adsorbent amount, and desorption circumstances) were evaluated. Optimized conditions for solid phase microextraction of ZOLM were pH 2.9, 5.0 mg Fe3O4/FeOOH MNCs, 15 min vortex-assisted extraction time and 3 × 200 µL of methanol: 33% ammonia; 4:1 as eluent. The analysis was achieved using ACN: dichloromethane: 33% ammonia (22.5: 6.0: 1.5, v/v/v) as a mobile phase and the fluorescence detection was carried out at 223 nm. The proposed DSPME method was successfully applied for trace quantification of ZOLM in rabbits' plasma (n = 6) after oral administration with a linearity range of 50.0 - 400.0 ng mL-1 (R2 = 0.9931), a detection limit of 12.0 ng mL-1 and extraction recovery of 97.27-99.89% with an RSD < 2% (n = 9). Moreover, the selectivity of the proposed approach for analysis of ZOLM in the presence of MET and PARA is demonstrated.

Fabrication of water compatible and biodegradable super-paramagnetic molecularly imprinted nanoparticles for selective separation of memantine from human serum prior to its quantification: An efficient and green pathway.

A novel green magnetic molecularly imprinted solid phase extraction (MMI-SPE) for separation of memantine (MEM) from complicated matrices was proposed. The nanomaterial was synthesized via crosslinking of chitosan (CHIT) with [3-(2, 3-epoxypropoxy)-propyl] trimethoxysilane (EPPTMS) in presence of MEM as a template. The nanocomposites, in all steps, were characterized by SEM, FTIR and PXRD techniques. The adsorbed drug was removed from magnetic molecular imprinted polymer (MMIP) cavity by ethanol: acetic acid (8:2, v/v) and then, coupled with sodium 1, 2-naphthoquinone-4-sulphonate (NQS) in iodine/alkaline medium to yield highly fluorescent product, after reduction with potassium borohydride (KBH4). Variables affecting extraction of MEM from imprinted sites and its fluorometric analysis were studied. The linearity was achieved over concentration range of 1.84-95.0 ng mL-1 with LOD of 0.6 ng mL-1. The method was successfully applied for determination of MEM in its pharmaceutical tablets and human serum with recoveries of 100.8 ±â€¯3.0, 97.6 ±â€¯2.9, respectively.

Determination of donepezil in spiked rabbit plasma by high-performance liquid chromatography with fluorescence detection.

The aim of this paper is to develop sensitive, accurate, reproducible and robust RP-HPLC with fluorescence detection for estimation of donepezil (DZ) in rabbit plasma using silodosin as the internal standard (IS). The prepared samples were quantified on reversed phase column Luna C18(2) (150 × 4.6 mm i.d., 5 µm particle size) operated at room temperature using the mobile phase consisting of methanol: 0.1% acetic acid (50 : 50, v/v) at a flow rate of 1 ml min-1. The method was fully validated according to bioanalytical validation guidelines of FDA in terms of system suitability, selectivity, sensitivity, precision and stability. It was found that the increase in peak areas followed the increase of DZ concentration in the range of 2.56-200.00 ng ml-1 with LOD of 0.85 ng ml-1. The method was successfully applied for the determination of DZ in rabbit plasma using manual shaking dispersive liquid-liquid microextraction.

A rapid Fourier transform infrared spectroscopic method for analysis of certain proton pump inhibitors in binary and ternary mixtures.

A simple and non-destructive FTIR method was used to determine certain proton pump inhibitors (PPIs) in binary and ternary mixtures. Proton pump inhibitors (PPIs); omeprazole (OMZ), esomeprazole (EZM), lansoprazole (LAN), pantoprazole sodium (PAN sodium) and rabeprazole sodium (RAB sodium) in binary mixture with domperidone (DOM) and ternary mixture of OMZ, clarithromycin (CLM) and tinidazole (TNZ) were determined in the solid-state by FTIR spectroscopy for the first time. The method was validated according to ICH-guidelines where linearity was ranged from 20 to 850µg/g and 20-360µg/g for PPIs and DOM, respectively in binary mixtures and 10-400, 100-8000 and 150-14,000µg/g for OMZ, CLM and TNZ, respectively. Limits of detection were found to be 6-100 and 9-100µg/g for PPIs and DOM, respectively and 4, 40 and 50µg/g for OMZ, CLM and TNZ, respectively. The method was applied successfully for determination of the cited drugs in their respective pharmaceutical dosage forms.

Development of a novel and cost-effective redox sensor for voltammetric determination of pantoprazole sodium during pharmacokinetic studies.

A pencil graphite electrode modified with poly (bromocresol green (BCG)) was prepared by electro-polymerization process for the determination of pantoprazole sodium. The surface morphology and structure of poly (BCG) film were characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. The determination of pantoprazole sodium in Britton-Robinson buffer (pH 7.0) was carried out by square wave adsorptive stripping voltammetric technique. Under optimum conditions, the linear response of the peak with concentration of the cited drug was in the range of 6.6-360 × 10-8 M with limit of detection of 2.2 × 10-8 M. Moreover, the poly (BCG)-modified electrode has been successfully applied to determine pantoprazole sodium in tablets, vials and during pharmacokinetic studies.

Simultaneous voltammetric analysis of anti-ulcer and D2-antagonist agents in binary mixture using redox sensor and their determination in human serum.

Pencil graphite electrode was successfully modified with a thin film of poly (eriochrome black T) and applied for the sensitive and selective voltammetric simultaneous determination of pantoprazole sodium and domperidone in a binary mixture. The preparation and basic electrochemical behavior of poly (eriochrome black T) film on the Pencil graphite electrode were investigated. The modified electrode has exhibited very high electro-catalytic activity towards the cited mixture. The anodic peaks of the both species were well defined with enhanced oxidation peak currents. Under the optimum conditions, the linearity ranges were 0.4-55×10-7M and 0.1-34×10-7M for pantoprazole sodium and domperidone, respectively with detection limits of 0.12×10-7M and 0.04×10-7M for pantoprazole sodium and domperidone, respectively. The proposed sensor has been successfully applied in the analysis of pantoprazole sodium and domperidone in synthetic binary mixtures and human serum.

A validated spectrofluorometric assay for the determination of certain macrolide antibiotics in pharmaceutical formulations and spiked biological fluids.

This paper describes a simple spectrofluorometric method for the analysis of 4 macrolide antibiotics. The method is based on the condensation of 10% (w/v) malonic acid and acetic acid anhydride under the catalytic effect of tertiary amine groups of the studied macrolides. The relative fluorescence intensity of the condensation product was measured at 397/452 nm (excitation/emission) for azithromycin dihydrate and at 392/445 nm (for clarithromycin, erythromycin ethylsuccinate, and roxithromycin. All variables affecting the reaction conditions were studied. The effects of potential interference due to common excipients, such as starch, lactose, sucrose, glucose, gum acacia, and magnesium stearate, as well as trimethoprim and sulfisoxazole acetyl formulated in primomycin capsules and pediazole oral suspension, respectively, were studied. A validation study for the proposed method was carried out according to U.S. Pharmacopeia 2002. The linearity ranges were 3-80 ng/mL for all of the cited macrolides. The limit of detection range was 0.74-1.20 ng/mL, while the limit of quantitation range was 2.47-4.02 ng/mL. The method was applied for the assay of the studied macrolides in pure pharmaceutical formulations and in spiked biological fluids. Results were compared with those obtained from the reported method, where calculated t- and F-values indicated high accuracy and good precision for the proposed method.

Spectrofluorimetric analysis of certain macrolide antibiotics in bulk and pharmaceutical formulations.

The macrolides (erythromycin, erythromycin esters, azithromycin dihydrate, clarithromycin and roxithromycin) can be analyzed by a simple spectrofluorimetric method based on the oxidation by cerium(VI) in the presence of sulphuric acid and monitoring the fluorescence of cerium(III) formed at lambda(ex) 255 nm and lambda(em) 348 nm. All variables affecting the reaction conditions as cerium(VI), sulphuric acid concentrations, heating time, temperature and dilution solvents were carefully studied. Linear calibration graphs were obtained in the range of 42.6-1200 ng ml(-1) with a percentage relative standard deviation in the range of 0.014-0.058%. Quantitation and detection limits were calculated. The method was applied successfully for the assay of the studied drugs in pure and pharmaceutical dosage forms as tablets, capsules and suspension. Recovery experiments revealed recovery of 98.3-100.8%. The effect of potential interference due to common ingredients as glucose, sucrose, lactose, citric acid, and propylene glycol was investigated. Applying standard addition method shows a recovery of 97.7-100.9% macrolide antibiotics from their corresponding dosage forms.