Determination of diminazene aceturate in pharmaceutical formulations by HPLC and identification of related substances by LC/MS

Diminazene aceturate attenuates systemic inflammation via microbiota gut-5-HT brain-spleen sympathetic axis in male mice

The sympathetic arm of the inflammatory reflex is the efferent pathway through which the central nervous system (CNS) can control peripheral immune responses. Diminazene aceturate (DIZE) is an antiparasitic drug that has been reported to exert protective effects on various experimental models of inflammation. However, the pathways by which DIZE promotes a protective immunomodulatory effects still need to be well established, and no studies demonstrate the capacity of DIZE to modulate a neural reflex to control inflammation. C57BL/6 male mice received intraperitoneal administration of DIZE (2 mg/Kg) followed by lipopolysaccharide (LPS, 5 mg/Kg, i.p.). Endotoxemic animals showed hyperresponsiveness to inflammatory signals, while those treated with DIZE promoted the activation of the inflammatory reflex to attenuate the inflammatory response during endotoxemia. The unilateral cervical vagotomy did not affect the anti-inflammatory effect of DIZE in the spleen and serum. At the same time, splenic denervation attenuated tumor necrosis factor (TNF) synthesis in the spleen and serum. Using broad-spectrum antibiotics for two weeks showed that LPS modulated the microbiota to induce a pro-inflammatory profile in the intestine and reduced the serum concentration of tryptophan and serotonin (5-HT), while DIZE restored serum tryptophan and increased the hypothalamic 5-HT levels. Furthermore, the treatment with 4-Chloro-DL-phenylalanine (pcpa, an inhibitor of 5-HT synthesis) abolished the anti-inflammatory effects of the DIZE in the spleen. Our results indicate that DIZE promotes microbiota modulation to increase central 5-HT levels and activates the efferent sympathetic arm of the inflammatory reflex to control splenic TNF production in endotoxemic mice.

Diminazene aceturate attenuates hepatic ischemia/reperfusion injury in mice

Hepatic ischemia/reperfusion (I/R) injury is one of the leading causes of mortality following partial hepatectomy, liver transplantation, hypovolemic shock and trauma; however, effective therapeutic targets for the treatment of hepatic I/R injury are lacking. Recent studies have shown that diminazene aceturate (DIZE) has protective effects against inflammation, oxidative stress and cell death, which are the main pathogenetic mechanisms associated with hepatic I/R injury. However, the mechanistic effects DIZE exerts on hepatic I/R remain unknown. C57BL/6 male mice were pretreated with either 15 mg/kg DIZE or vehicle control (saline) and subjected to partial liver ischemia for 60 min. One day after induction of hepatic I/R, liver damage, inflammatory responses, oxidative stress and apoptosis were analyzed. By evaluating plasma alanine aminotransferase levels and histology, we found that DIZE treatment attenuated liver failure and was associated with a reduction in histologically-apparent liver damage. We also found that DIZE-treated mice had milder inflammatory responses, less reactive oxidative damage and less apoptosis following hepatic I/R compared to vehicle-treated mice. Taken together, our study demonstrates that DIZE protects against ischemic liver injury by attenuating inflammation and oxidative damage and may be a potential therapeutic agent for the prevention and treatment of ischemic liver failure.

In silico investigation of the therapeutic and prophylactic potential of medicinal substances bearing guanidine moieties against COVID-19

The current viral pandemic, coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), creates health, mental, economic, and other serious challenges that are better to say global crisis. Despite the existence of successful vaccines, the possible mutations which can lead to the born of novel and possibly more dangerous variants of the virus as well as the absence of definitive treatment for this potentially fatal multiple-organ infection in critically ill patients make us keep searching. Theoretically targeting human and viral receptors and enzymes via molecular docking and dynamics simulations can be considered a wise, rational, and efficient way to develop therapeutic agents against COVID-19. In this way, The RNA-dependent RNA polymerase (RdRP), main protease, and spike glycoprotein of SARS-CoV-2 as well as the human angiotensin-converting enzyme 2 receptor and transmembrane serine protease 2 are the most discussed and studied targets that play essential roles in the viral life and infection cycle. In the current in silico investigation, the guanidine functionality containing drugs and medicinal substances such as metformin, famotidine, neuraminidase inhibitors, antimalarial medications, anticancer drug imatinib, CGP compounds, and human serine protease inhibitor camostat were studied against the above-mentioned therapeutic targets and most of them (especially imatinib) have revealed an incredible spectrum of free docking scores and MD results. The current in silico investigation that its novel perspective of view is corroborated by the different experimental and clinical evaluations, confirms that the guanidine moiety can be considered as a missing promising pharmacophore in drug design and development approaches against SARS-CoV-2. Considering the chemical potency of this polyamine group in chemical interaction creation, the observed outcomes in this virtual screening were not surprising. On the other hand, the guanidine functional group has unique physico-chemical properties such as basicity that can make the target cells intracellular pH undesirable for the virus entry, uncoating, and cytosolic lifecycle. According to the obtained results in the current study that are interestingly confirmed by the previously reported efficacy of some the guanidine carrying drugs in COVID-19, guanidine as a potential multi-target anti-SARS-CoV-2 functional scaffold deserves further comprehensive investigations.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11696-022-02528-y.

Ultrasensitive immunochromatographic strip assay for the detection of diminazene

We prepared monoclonal antibodies (mAbs) against diminazene and used them in the development of a gold nanoparticle-based lateral-flow test (GNT) strip and indirect competitive enzyme-linked immunosorbent assay for the detection of diminazene in beef and beef liver samples. MAbs, which belong to the IgG2a subclass, had a half maximal inhibitory concentration of 0.04 ng mL^-1. Based on cross-reactivity, mAb against diminazene was highly specific. The visual limit of detection (vLOD) of the GNT strip was 0.1 μg kg^-1, and the cut-off value was 1 μg kg^-1 in beef samples. The vLOD of the GNT assay was 0.1 μg kg^-1, and the cut-off value was 2 μg kg^-1 in beef liver samples. The average recoveries of diminazene ranged from 97.5% to 103.7% when using ic-ELISA. The accuracy of the developed GNT strip was confirmed by comparing the results with the ic-ELISA results. We developed a reliable GNT strip assay for the rapid detection of diminazene in beef and beef liver samples.

Development of a High-Throughput Affinity Mass Spectrometry (AMS) Platform Using Laser Diode Thermal Desorption Ionization Coupled to Mass Spectrometry (LDTD-MS)

Affinity selection mass spectrometry (MS) or, simply, affinity mass spectrometry (AMS) is a label-free technology that has been used to identify high-affinity ligands of target proteins of interest by screening against small-molecule compound libraries and identifying molecules that are enriched in the presence of the target protein. We have previously applied Agilent Technology's (Santa Clara, CA) RapidFire solid-phase extraction (SPE)-based high-throughput MS technology to screen small-molecule libraries using AMS. However, SPE-based technologies rely on fluidics for desalting and separation prior to mass analysis with attendant high solvent consumption, relatively high sample volume requirements, risk of sample carryover, and frequent maintenance. To address these challenges, we have established an AMS platform using a laser diode thermal desorption-atmospheric pressure chemical ionization (LDTD-APCI) ionization source (Phytronix, Quebec, Canada) coupled with a SCIEX 5600+ TripleTOF MS (Framingham, MA). We also validated a data-independent acquisition (DIA) Sequential Window Acquisition of All Theoretical Mass Spectra (SWATH-MS) method for the robust detection and analysis of small-molecule affinity hits. An informatics platform developed in-house has resulted in a streamlined data analysis workflow for high-throughput AMS screening campaigns and reduced data processing time without compromising data quality. Finally, 68,000 compounds were screened in a single plate and affinity selected hits were confirmed in an orthogonal enzyme activity assay.

New spectral resolution techniques for resolving and determining the components in binary fixed-dose combinations

Four spectrophotometric approaches were performed to determine a binary combination of Phenazone and Benzocaine in pure powder form and in pharmaceutical formations. This investigation submits the application of four techniques contingent on the presence of the extended area of the spectra of one compound in the binary mixture, these methods include Absorptivity Centering (a-centering), Absorbance Subtraction (AS), Amplitude Modulation (AM) and Concentration Value (CV). The linearity range for the above-mentioned approaches was found to be 3.0-15.0 μg/mL for Benzocaine in a-centering method and 3.0-30.0 μg/mL for Benzocaine and Phenazone in other advanced methods. The four techniques were evaluated as per ICH criteria and were successfully utilized for the determination of Phenazone and Benzocaine existing in pharmaceutical formulations. All results gained by the submitted approaches were statistically compared with a previously published method, and no important differences were detected.

Multi-residue analysis using liquid chromatography tandem mass spectrometry for detection of 20 coccidiostats in poultry, livestock, and aquatic tissues

In this study, we developed a novel analysis method based on liquid chromatography/tandem mass spectrometry (LC-MS/MS) to allow the simultaneous identification of 20 coccidiostats in eight matrix categories, including the muscles of chicken, swine, cow, and fish as well as chicken eggs, bovine milk, and porcine viscera. In the pretreatment procedure, acetonitrile/methanol (95:5, v/v) containing 1% formic acid, 5 g of sodium acetate, and 6.0 g of anhydrous magnesium sulfate was used for extraction, followed by a clean-up procedure using n-hexane saturated with ACN to facilitate the elimination of analytes from high lipid samples. Chromatographic separations were achieved using a Poroshell 120SB C18 column and operated with a gradient mobile phase system consisting of methanol (with 0.1% formic acid) and 5 mM ammonium formate, and the MS detection was monitored simultaneously. The method was validated in accordance with the Guidelines for the Validation of Food Chemical Methods by the Taiwan Food and Drug Administration. The limit of quantitation among 8 matrices were 0.5-2 ng g-1. The proposed method proved highly effective in detecting the presence of targeted veterinary drugs, providing a high degree of precision and accuracy over a broad range of matrices.

β-Cyclodextrin as a Functional Excipient Used for Enhancing the Diminazene Aceturate Bioavailability

In this study, we proposed formulations of diminazene aceturate (DA) designed to improve its bioavailability and to maximize the therapeutic index in animals by overcoming the rapid degradation under the acidic pH of the stomach. An important consequence is the fact that its amount in the bloodstream is close to the administered dose. This was made possible by incorporating DA into the β-cyclodextrin’s (βCD) cavity in a molar ratio of 1:1. The structure of the resulted inclusion complex was established by Raman, DSC, and Wide-Angle X ray Diffraction (WAXD) in solid state and by ¹H-NMR and H-H ROESY in aqueous solutions. The stoichiometry of the DA:βCD inclusion complex was obtained by using the continuous variation method (Job’s plot), considering the chemical shifts variations of protons from both DA and βCD compounds in ¹H-NMR spectra. The biological activity was estimated in vitro by antioxidant activity and in vivo by comparing the bioavailability of parent DA and its inclusion complexes after a single dose administration in Wistar rats by using the HPLC method on their blood plasma. In vitro tests showed an improved antioxidant activity. In vivo tests have shown that the DA concentration is always much higher in blood plasma of rats when DA:βCD inclusion complex of 1:1 molar ratio was administered (i.e., at 60 min, DA is around 11 and 3 times higher when DA:βCD inclusion complex of 1:1 molar ratio was administered than the parent DA one and DA:βCD lyophilized mixture of 1:2 molar ratio, respectively).

Simultaneous Determination and Stability Studies on Diminazene Diaceturate and Phenazone Using Developed Derivative Spectrophotometric Method

This work presents UV first derivative spectrophotometry as a precise, accurate, and feasible method for simultaneous determination of diminazene diaceturate and phenazone in bulk and dosage forms. The absorbance values of diminazene diaceturate and phenazone aqueous mixture were obtained at 398 nm and 273 nm, respectively. The developed method was proved to be linear over the concentration ranges (2–10) μg/mL and (2.496–12.48) μg/mL for diminazene diaceturate and phenazone, respectively, with good correlation coefficients (not less than 0.997). The detection and quantitation limits were found to be (LOD = 0.63 and 0.48 μg/mL; LOQ = 1.92 and 1.47 μg/mL, resp.). The developed method was employed for stability studies of both drugs under different stress conditions. Diminazene diaceturate was prone to degrade at acidic pH via first-order kinetics. The degradation process was found to be temperature dependent with an activation energy of 7.48 kcal/mole. Photo-stability was also investigated for this drug.

Titanium nanoparticles (TiO2)/graphene oxide nanosheets (GO): an electrochemical sensing platform for the sensitive and simultaneous determination of benzocaine in the presence of antipyrine

An effective electrochemical sensing platform for the simultaneous determination of benzocaine (BEN) and antipyrine (ANT).

Drug quality analysis through high performance liquid chromatography of isometamidium chloride hydrochloride and diminazene diaceturate purchased from official and unofficial sources in Northern Togo

Trypanocidal drugs remain the most accessible and thus commonly used means of controlling tsetse transmitted animal African trypanosomosis. In Togo, trypanocides are sold on official as well as unofficial markets, but the quality of these trypanocides is undocumented so a drug quality assessment study was conducted from May 2013 to June 2014. Trypanocides supplied by European, Indian and Chinese pharmaceutical companies and sold on official and unofficial markets in Togo were purchased. In total fifty-two trypanocides were obtained, 24 of these samples from official markets and 28 from unofficial markets made up of a total of 36 diminazene diaceturate and 16 isometamidium chloride hydrochloride samples. The samples were analysed in the reference laboratory of the OIE (World Organisation for Animal Health), Laboratory for the Control of Veterinary Medicines (LACOMEV) in Dakar which uses galenic testing and high performance liquid chromatography (HPLC) testing as standard reference analysis methods. The results revealed a high proportion of trypanocides of sub-standard quality on the Togolese market: 40% were non-compliant to these quality reference standards. All of the HPLC non-compliant samples contained lower amounts of active ingredient compared to the concentration specified on the packaging. Non-compliance was higher in samples from the unofficial (53.57%) than from the official markets (25%; p=0.04).The main drug manufacturers, mostly of French origin in the study area, supply quality drugs through the official legal distribution circuit. Products of other origins mostly found on illegal markets present a significantly lower quality.

A novel surfactant silica gel modified carbon paste electrode in micellar media for selective determination of diminazene aceturate in the presence of its stabilizer

A novel irreversible anodic voltammetric method was introduced for selective determination of diminazene aceturate in the presence of phenazone as a stabilizer.

Liposomes produced by reverse phase evaporation: in vitro and in vivo efficacy of diminazene aceturate against Trypanosoma evansi

This study aimed to develop and test the in vitro and in vivo effectiveness of diminazene aceturate encapsulated into liposomes (L-DMZ) on Trypanosoma evansi. To validate the in vitro tests with L-DMZ, the efficacy of a commercial formulation of diminazene aceturate (C-DMZ) was also assessed. The tests were carried out in culture medium for T. evansi, at concentrations of 0.25, 0.5, 1, 2 and 3 μg mL(-1) of L-DMZ and C-DMZ. A dose-dependent effect was observed for both formulations (L-DMZ and C-DMZ), with the highest dose-dependent mortality of trypomastigotes being observed at 1 and 3 h after the onset of tests with L-DMZ. The results of in vivo tests showed the same effects in the animals treated with L-DMZ and C-DMZ in single doses of 3.5 mg kg(-1) and for 5 consecutive days (3.5 mg kg(-1) day(-1)). It was possible to conclude that T. evansi showed greater in vitro susceptibility to L-DMZ when compared with C-DMZ. In vivo tests suggest that treatment with the L-DMZ and C-DMZ showed similar efficacy in vivo. The potential of the formulation developed in this study was clearly demonstrated, as it increased the efficacy of the treatment against trypanosomosis, but more studies are needed to increase the effectiveness in vivo.

Development of a nanoparticulate formulation of diminazene to treat African trypanosomiasis

There is a real need to develop new therapeutic strategies for African trypanosomiasis infections. In our study, we developed a new drug delivery system of diminazene (DMZ), a trypanocidal drug registered for veterinary use. This drug candidate presents a limited efficacy, a poor affinity for brain tissue and instability. The development of colloidal formulations based on a porous cationic nanoparticle with an oily core ((70)DGNP(+)), has potentially two advantages: stabilization of the drug and potential targeting of the parasite. We analyzed two processes of drug loading: in process (DMZ was added during the preparation of (70)DGNP(+) at 80 °C) and post-loading (DMZ was mixed with a (70)DGNP(+) solution at room temperature). Poor stability of the drug was observed using the in process technique. When using the post-loading technique over 80% drug entrapment efficiency was obtained at a ratio of DMZ:phospholipids (wt:wt) < 5%. Moreover, DMZ loaded into (70)DGNP(+) was found to be protected against oxidation and was stable for at least six months at 4 °C. Finally, in vitro tests on T.b. brucei showed an increased efficacy of DMZ loaded in (70)DGNP(+).

Enhancement of hydrophilic drug loading and release characteristics through micellization with new carboxymethyldextran-PEG block copolymers of tunable charge density

The micellization of a model cationic drug, diminazene diaceturate (DIM) and a series of new diblock copolymers, carboxymethyldextran-poly(ethylene glycols) (CMD-PEG), were evaluated as a function of the ionic charge density or degree of substitution (DS) of the carboxymethyldextran block and the molar ratio, [+]/[-], of positive charges provided by the drug to negative charges provided by CMD-PEG. Micelles ([+]/[-]=2) incorporated up to 64% (w/w) DIM and ranged in hydrodynamic radius (R(H)) from 36 to 50 nm, depending on the molecular weight and DS of CMD-PEG. The critical association concentration (CAC) was on the order of 15-50mg/L for CMD-PEG of DS>60%, and ca. 100mg/L for CMD-PEG of DS approximately 30%. The micelles were stable upon storage in solution for up to 2 months and after freeze-drying in the presence of trehalose. They remained intact within the 4<pH<11 range and for solutions of pH 5.3, they resisted increases in salinity up to approximately 0.4M NaCl in the case of CMD-PEG of high DS. However, micelles of DIM and a CMD-PEG of low DS (30%) disintegrated in solutions containing more than 0.1M NaCl, setting a minimum value to the DS of copolymers useful in in vivo applications. Sustained in vitro DIM release was observed for micelles of CMD-PEG of high DS ([+]/[-]=2).

A diminazene-resistant strain ofTrypanosoma brucei bruceiisolated from a dog is cross-resistant to pentamidine in experimentally infected albino rats

Trypanosomosis is a major cause of mortality for dogs in Nigeria and treatment with diminazene aceturate has steadily become less effective, either as a result of low quality of the locally available diminazene preparations or of drug resistance. To investigate these alternatives, samples of locally obtained drugs were analysed for diminazene aceturate content and a strain ofTrypanosoma brucei bruceiwas isolated from a diminazene-refractory dog in Nsukka, south-eastern Nigeria, and used to infect albino rats. The quality of diminazene aceturate-based preparations was variable, with two preparations containing less than 95% of the stated active compound. Rats infected withT. bruceiisolated from the dog were treated 7 and 10 days after infection either with 7 mg/kg diminazene aceturate (intraperitoneally, once) or with 4 mg/kg pentamidine isethionate (intramuscularly, 7 consecutive days). Relapse rates were 100% for both trypanocides in the groups of rat treated 10 days post-infection, and 83% and 50% of rats treated 7 days after infection relapsed to diminazene aceturate and pentamidine isethionate, respectively. Careful consideration of physiological parameters showed that pentamidine was only marginally superior to diminazene aceturate as applied in this study. It was concluded that dogs in Nigeria are infected with genuinely diminazene aceturate-resistant trypanosomes that appear to be cross-resistant to pentamidine isethionate.

Determination of active ingredient within pharmaceutical preparations using flow injection mass spectrometry

Two separate pharmaceutical blends, one containing 2% caffeine by weight, the other containing 2% creatine by weight, and 200 mg caffeine tablets were examined in this study. The purpose of the analyses was to determine the feasibility of using flow injection mass spectrometry for the quantitative analysis of active ingredient within a drug product or other form of pharmaceutical preparation. For more precise and accurate measurements, it was necessary to incorporate an internal reference within the samples. Further, flow injection analysis showed to provide quicker, more facile method development than the application of chromatographic separation. Samples were analyzed over an analyte concentration range of 5.0-15.0 microg/mL. Analyte selectivity was obtained through the observance of the (M+H)(+) ions generated by positive electrospray ionization of each of the analytes (m/z 195 for caffeine and m/z 132 for creatine), and accurate quantitation was achieved by determining the ratio of the analyte response versus the response of the incorporated reference compound. Sample-to-sample precision in these measurements was less than 3%, recovery values were shown to be accurate to within +/-3% of the actual values, and both analytical methods proved to be linear over the assay range (R(2)> or =0.999). Due to the excellent selectivity and low detection limits available to mass spectrometric detection, flow injection mass spectrometric analysis could be particularly applicable for analysis of formulations that contain either low doses of active ingredient, active ingredient with low solubility, or active ingredient that does not possess a strong chromophore. Additionally, this type of methodology shows to be conducive for rapid method development.

Characterization of Caco-2 cell monolayer drug transport properties by cassette dosing using UV/fluorescence HPLC

Cassette dosing is commonly used in pharmacokinetic studies to decrease time, labor and expenditures. Cassette dosing (having several compounds in a mixture) has been used to screen in vitro permeabilities in Caco-2 cell monolayers. The cassette dosing method has accelerated both transport experiments and sample analyses, which are both part of Caco-2 permeability screening. In this study, a cassette dosing method was used for a mixture of heterogeneous test drugs, which are transported by various mechanisms across the Caco-2 cell monolayer. To characterize the Caco-2 cell monolayer absorption properties, we developed a new UV/fluorescence HPLC method for nine heterogeneous drugs. This new analytical method is fast and specific for high throughput analysis. Fluorescence detection was used to analyze the low concentration of drugs while UV detection was suitable for higher concentrations. The permeability results of single drugs and the mixture of drugs showed a high degree of similarity for each individual compound. All drugs can be applied to the Caco-2 cell culture as a mixture, and the cassette dosing method is suitable for permeability studies.

The effect of inducing agents on the metabolism of trypanocidal diamidines by isolated rat hepatocytes

This study has investigated the effect of phenobarbitone (PB), 3-methylcholanthrene (3-MC), and deltamethrin (DM) on the metabolism of two trypanocidal diamidines; pentamidine isethionate and diminazene aceturate in freshly isolated Sprague-Dawley rat hepatocytes. There were significant increases in the total cytochrome p450 content of hepatocytes obtained from rats pre-treated with PB and 3-MC, whereas pre-treatment with DM did not produce any significant induction of cytochrome p450. However, pre-treatment of rats with each of the three agents led to inhibition of pentamidine metabolism following a 3h incubation of pentamidine (100 microM) with freshly isolated rat hepatocytes (5 x 10(6) cells ml(-1)). Pre-treatment with 3-MC caused the highest inhibitory effect on pentamidine metabolism (8-fold inhibition), compared with PB (4.8-fold) and DM (2.2-fold). Six previously reported phase I metabolites of pentamidine were identified in cells from all the pre-treated animals as well as controls. When compared to the control group, there were significant differences between the profiles of the three major metabolites of pentamidine, 1,5-di(4'-amidinophenoxy)-2-pentanol, 1,5-di(4'-amidinophenoxy)-3-pentanol and 5-(4'-amidinophenoxy) pentanoic acid, in hepatocytes from the DM and 3-MC pre-treated rats, whereas no significant differences were observed in the cells from the PB pre-treated group. In contrast, diminazene was not metabolised with the same experimental conditions. Differences in the metabolic profiles of pentamidine and its metabolites as a result of concomitant exposure to environmental xenobiotics could have important toxicological and pharmacological implications for patients that receive the drug.