Solid dispersion systems for enhanced dissolution of poorly water-soluble candesartan cilexetil: In vitro evaluation and simulated pharmacokinetics studies.

BACKGROUND: Candesartan cilexetil (CC) is a selective angiotensin II receptor antagonist widely used to treat hypertension. CC is a substrate of P-glycoprotein (P-gp), causing its efflux to the intestinal lumen. It is also practically insoluble in water and has low oral bioavailability (14%). Thus, the current study aims to improve the in vitro dissolution of CC by developing solid dispersion systems (SDSs) and corroborating the in vitro results using a simulated pharmacokinetics study. METHODS: The SDSs were prepared using polyvinyl pyrrolidone (PVP) as a water-soluble polymer, Eudragit E100 (EE100) as a pH-dependent soluble carrier, and a combination of these two polymers. The saturation solubility and the dissolution rate studies of the prepared systems in three dissolution media were performed. The optimized system SE-EE5 was selected for further investigations, including DSC, XRD, FTIR, FESEM, DLS, TSEM, IVIVC convolution study, and stability studies. RESULTS: The solubility of CC significantly increased by a factor of 27,037.344 when formulated as a solid dispersion matrix using EE100 at a ratio of 1:5 (w/w) drug to polymer (SE-EE5 SD), compared to the solubility of the pure drug. The mechanism of solubility and dissolution rate enhancement of CC by the optimized SDS was found to be via the conversion of the crystalline CC into the amorphous form as well as nanoparticles formation upon dissolution at a pH below 5. The instrumental analysis tests showed good compatibility between CC and EE100 and there was no chemical interaction between the drug and the polymer. Moreover, the stability tests confirmed that the optimized system was stable after three months of storage at 25°C. CONCLUSION: The utilization of the solid dispersion technique employing EE 100 polymer as a matrix demonstrates significant success in enhancing the solubility, dissolution, and subsequently, the bioavailability of water-insoluble drugs like CC.

Vicinal diaryl pyrazole with tetrazole/urea scaffolds as selective angiotensin converting enzyme-1/cyclooxygenase-2 inhibitors: Design, synthesis, anti-hypertensive, anti-fibrotic, and anti-inflammatory.

As a hybrid weapon, two novel series of pyrazoles, 16a-f and 17a-f, targeting both COX-2 and ACE-1-N-domain, were created and their anti-inflammatory, anti-hypertensive, and anti-fibrotic properties were evaluated. In vitro, 17b and 17f showed COX-2 selectivity (SI = 534.22 and 491.90, respectively) compared to celecoxib (SI = 326.66) and NF-κB (IC50 1.87 and 2.03 µM, respectively). 17b (IC50 0.078 µM) and 17 f (IC50 0.094 µM) inhibited ACE-1 comparable to perindopril (PER) (IC50 0.048 µM). In vivo, 17b decreased systolic blood pressure by 18.6%, 17b and 17f increased serum NO levels by 345.8%, and 183.2%, respectively, increased eNOS expression by 0.97 and 0.52 folds, respectively and reduced NF-κB-p65 and P38-MAPK expression by -0.62, -0.22, -0.53, and -0.24 folds, respectively compared to  l-NAME (-0.34, -0.45 folds decline in NF-κB-p65 and P38-MAPK, respectively). 17b reduced ANG-II expression which significantly reversed the cardiac histological changes induced by L-NAME.

Solidification of deep eutectic solvent containing fimasartan through wet impregnation and exploration of flow attributes by modified SeDeM-SLA expert system.

The solidification of deep eutectic solvent (DES) through wet impregnation techniques on inert solid carriers is an interesting approach that offers better processing attributes and excellent stability. Herein, DES of Fimasartan (FS) was developed to improve its solubility and bioavailability. The selected DES-FS was solidified by wet impregnation method employing Nesulin US2 and Aerosil 200. The SeDeM-SLA (solid-liquid adsorption) system was employed to investigate flow attributes of solidified DES-FS. Further, the selected solidified DES-FS (A) was characterized by Fourier transforms infrared spectroscopy (FTIR), Powder X-ray diffraction (PXRD), Differential scanning calorimetry (DSC), Scanning electron microscopy (SEM). The DES comprising Choline Chloride (ChCl): Glycerol (Gly) (1:3) revealed maximum drug solubility (35.6 ± 2.2 mg/mL) and thus opted for solidification. Solidification through wet impregnation was employed using 1:0.5 ratios (DES-FS to carriers). The Index of Good Flow (IGF) value was calculated from the SeDeM-SLA expert system, which indicates the better flow characteristics of solidified DES-FS, particularly with Neusilin US2 [SDES-FS (A)]. The solid-state evaluation data of SDS-FS (A) suggested a transition of FS to an amorphous form, resulting in an increment in solubility and dissolution. A similar trend was reported in the in vivo pharmacokinetic study, which indicated a 2.9 folds increment in the oral bioavailability of FS. Furthermore, excellent stability, i.e., a shelf life of 28.44 months, reported by SDES-FS (A) in accelerated stability studies, suggests better formulation perspectives. In a nutshell, the present study evokes the potentiality of performing solidification through wet impregnation and successful implementation of the SeDeM-SLA expert model, which could find wide applications in pharmaceutical science.

Innovative orthogonal two-dimensional reversed-phase liquid chromatography × supercritical fluid chromatography with a phenyl/tetrazole stationary phase for the preparative isolation of diarylheptanoids.

In this investigation, we successfully isolated and purified natural diarylheptanoids using an orthogonal offline two-dimensional RPLC × SFC approach, employing only the phenyl/tetrazole stationary phase. First, a styrene-divinylbenzene matrix medium pretreatment liquid chromatography system effectively processed chlorophyll-containing plant extract solution with a recovery rate of 33.8 %, obviating the need for concentration steps. Subsequently, an offline two-dimensional RPLC × SFC employing only the phenyl/tetrazole stationary phase achieved a remarkable 96.38 % orthogonality and was established and utilized in the preparative separation and purification of natural products. Finally, the constructed single stationary phase highly orthogonal RPLC × SFC system was successfully applied in the preparative separation and purification of natural diarylheptanoids from the Saxifraga tangutica target fraction and yielded four diarylheptanoids with purities exceeding 95 %.

Discovery of a Novel Potent Tetrazole Antifungal Candidate with High Selectivity and Broad Spectrum.

Thirty-one novel albaconazole derivatives were designed and synthesized based on our previous work. All compounds exhibited potent in vitro antifungal activities against seven pathogenic fungi. Among them, tetrazole compound D2 was the most potent antifungal with MIC values of <0.008, <0.008, and 2 µg/mL against Candida albicans, Cryptococcus neoformans, and Aspergillus fumigatus, respectively, the three most common and critical priority pathogenic fungi. In addition, compound D2 also exhibited potent activity against fluconazole-resistant C. auris isolates. Notably, compound D2 showed a lower inhibitory activity in vitro against human CYP450 enzymes as well as a lower inhibitory effect on the hERG K+ channel, indicating a low risk of drug-drug interactions and QT prolongation. Moreover, with improved pharmacokinetic profiles, compound D2 showed better in vivo efficacy than albaconazole at reducing fungal burden and extending the survival of C. albicans-infected mice. Taken together, compound D2 will be further investigated as a promising candidate.

Bioisoteres for carboxylic acids: From ionized isosteres to novel unionized replacements.

Carboxylic acids are key pharmacophoric elements in many molecules. They can be seen as a problem by some, due to perceived permeability challenges, potential for high plasma protein binding and the risk of forming reactive metabolites due to acyl-glucuronidation. By others they are viewed more favorably as they can decrease lipophilicity by adding an ionizable center which can be beneficial for solubility, and can add enthalpic interactions with the target protein. However, there are many instances where the replacement of a carboxylic acid with a bioisosteric group is required. This has led to the development of a number of ionizable groups which sufficiently mimic the carboxylic acid functionality whilst improving, for example, the metabolic profile of the molecule in question. An alternative strategy involves replacement of the carboxylate by neutral functional groups. This review initially details carefully selected examples whereby tetrazoles, acyl sulfonamides or isoxazolols have been beneficially utilized as carboxylic acid bioisosteres altering physicohemical properties, interactions with the target and metabolism and/or pharmacokinetics, before delving further into the binding mode of carboxylic acid derivatives with their target proteins. This analysis highlights new ways to consider the replacement of carboxylic acids by neutral bioisosteric groups which either rely on hydrogen bonds or cation-π interactions. It should serve as a useful guide for scientists working in drug discovery.

Tetrazole derivatives in the management of neurological disorders: Recent advances on synthesis and pharmacological aspects.

Neurological disorders are the leading cause of a large number of mortalities and morbidities. Nitrogen heterocyclic compounds have been pivotal in exhibiting wide array of therapeutic applications. Among them, tetrazole is a ubiquitous class of organic heterocyclic compounds that have attracted much attention because of its unique structural and chemical properties, and a wide range of pharmacological activities comprising anti-convulsant effect, antibiotic, anti-allergic, anti-hypertensive to name a few. Owing to significant chemical and biological properties, the present review aimed at highlighting the recent advances in tetrazole derivatives with special emphasis on their role in the management of neurological diseases. Besides, in-depth structure-activity relationships, molecular docking studies, and associated modes of action of tetrazole derivatives evident in in vitro, in vivo preclinical, and clinical studies have been discussed.

Synthesis of Cycloartan-16ß-ol from 16ß 24R-Epoxy-Cycloartane and Their Cytotoxicity Evaluation Against Human Cancer Cell Lines.

It was found that Argentatins A and B triterpenoids make up approximately 20-30 % of the waste resin produced from the industrial processes to isolate rubber from P. argentatum. We have developed an efficient protocol for synthesizing cycloartane-16ß-ol derivatives by opening the oxepane ring of argentatin B acetate (2) with BF3-OEt2. Although three new cycloartenol derivatives showed high cytotoxicity against PC-3 and HCT-15 cancer cell lines, nevertheless, the best results were obtained for (16ß,24R) -(16,24-epoxy-cycloartan-2(1H)-ylidene) acetate (14), compound with intact oxepane ring. These results indicate that the substituents in the argentatin nucleus and a side chain account for the cytotoxic activity. However, according to the selectivity index (SI), 14 did not show selectivity activity to cancer cell lines over the HaCat noncancerous cell line. The compound 3ß,16ß-Dihydroxy-cycloartan-24-one (5), synthesized by oxepane opening, demonstrated high cytotoxic activity to cancer cell lines and showed a remarkable selectivity to cancer cell lines over the noncancerous ones. These results suggest that 5 could lead to the development of new anticancer compounds.

Nitrile Imines as Peptide and Oligonucleotide Photo-Cross-Linkers in Gas-Phase Ions.

Nitrile imines produced by photodissociation of 2,5-diaryltetrazoles undergo cross-linking reactions with amide groups in peptide-tetrazole (tet-peptide) conjugates and a tet-peptide-dinucleotide complex. Tetrazole photodissociation in gas-phase ions is efficient, achieving ca. 50% conversion with 2 laser pulses at 250 nm. The formation of cross-links was detected by CID-MS3 that showed structure-significant dissociations by loss of side-chain groups and internal peptide segments. The structure and composition of cross-linking products were established by a combination of UV-vis action spectroscopy and cyclic ion mobility mass spectrometry (c-IMS). The experimental absorption bands were found to match the bands calculated for vibronic absorption spectra of nitrile imines and cross-linked hydrazone isomers. The calculated collision cross sections (CCSth) for these ions were related to the matching experimental CCSexp from multipass c-IMS measurements. Loss of N2 from tet-peptide conjugates was calculated to be a mildly endothermic reaction with ΔH0 = 80 kJ mol-1 in the gas phase. The excess energy in the photolytically formed nitrile imine is thought to drive endothermic proton transfer, followed by exothermic cyclization to a sterically accessible peptide amide group. The exothermic nitrile imine reaction with peptide amides is promoted by proton transfer and may involve an initial [3 + 2] cycloaddition followed by cleavage of the oxadiazole intermediate. Nucleophilic groups, such as cysteine thiol, did not compete with the amide cyclization. Nitrile imine cross-linking to 2'-deoxycytidylguanosine was found to be >80% efficient and highly specific in targeting guanine. The further potential for exploring nitrile-imine cross-linking for biomolecular structure analysis is discussed.

Unexpected Cyclization Product Discovery from the Photoinduced Bioconjugation Chemistry between Tetrazole and Amine.

Bioconjugation chemistry has emerged as a powerful tool for the modification of diverse biomolecules under mild conditions. Tetrazole, initially proposed as a bioorthogonal photoclick handle for 1,3-dipolar cyclization with alkenes, was later demonstrated to possess broader photoreactivity with carboxylic acids, serving as a versatile bioconjugation and photoaffinity labeling probe. In this study, we unexpectedly discovered and validated the photoreactivity between tetrazole and primary amine to afford a new 1,2,4-triazole cyclization product. Given the significance of functionalized N-heterocycles in medicinal chemistry, we successfully harnessed the serendipitously discovered reaction to synthesize both pharmacologically relevant DNA-encoded chemical libraries (DELs) and small molecule compounds bearing 1,2,4-triazole scaffolds. Furthermore, the mild reaction conditions and stable 1,2,4-triazole linkage found broad application in photoinduced bioconjugation scenarios, spanning from intramolecular peptide macrocyclization and templated DNA reaction cross-linking to intermolecular photoaffinity labeling of proteins. Triazole cross-linking products on lysine side chains were identified in tetrazole-labeled proteins, refining the comprehensive understanding of the photo-cross-linking profiles of tetrazole-based probes. Altogether, this tetrazole-amine bioconjugation expands the current bioconjugation toolbox and creates new possibilities at the interface of medicinal chemistry and chemical biology.

Both Nitro Groups Are Essential for High Antitubercular Activity of 3,5-Dinitrobenzylsulfanyl Tetrazoles and 1,3,4-Oxadiazoles through the Deazaflavin-Dependent Nitroreductase Activation Pathway.

3,5-Dinitrobenzylsulfanyl tetrazoles and 1,3,4-oxadiazoles, previously identified as having high in vitro activities against both replicating and nonreplicating mycobacteria and favorable cytotoxicity and genotoxicity profiles were investigated. First we demonstrated that these compounds act in a deazaflavin-dependent nitroreduction pathway and thus require a nitro group for their activity. Second, we confirmed the necessity of both nitro groups for antimycobacterial activity through extensive structure-activity relationship studies using 32 structural types of analogues, each in a five-membered series. Only the analogues with shifted nitro groups, namely, 2,5-dinitrobenzylsulfanyl oxadiazoles and tetrazoles, maintained high antimycobacterial activity but in this case mainly as a result of DprE1 inhibition. However, these analogues also showed increased toxicity to the mammalian cell line. Thus, both nitro groups in 3,5-dinitrobenzylsulfanyl-containing antimycobacterial agents remain essential for their high efficacy, and further efforts should be directed at finding ways to address the possible toxicity and solubility issues, for example, by targeted delivery.

Discovery and characterization of novel TRPML1 agonists.

Screening a library of >100,000 compounds identified the substituted tetrazole compound 1 as a selective TRPML1 agonist. Both enantiomers of compound 1 were separated and profiled in vitro and in vivo. Their selectivity, ready availability and CNS penetration should enable them to serve as the tool compounds of choice in future TRPML1 channel activation studies. SAR studies on conformationally locked macrocyclic analogs further improved the TRPML1 agonist potency while retaining the selectivity.

One-pot synthesis, computational chemical study, molecular docking, biological study, and in silico prediction ADME/pharmacokinetics properties of 5-substituted 1H-tetrazole derivatives.

An efficient synthesis of 5-substituted 1H-tetrazoles was successfully achieved through one-pot multi-component condensation reactions of some aromatic aldehydes or indolin-2,3-dione with malononitrile and sodium azide using diverse reaction conditions to obtain considerable product yields. Furthermore, it has been achieved for the first time to construct desired products under neat condition. Molecular docking studies with CSNK2A1 receptor disclosed the lowest binding energy displayed by the dimethoxyphenyl derivative 4c with - 6.8687 kcal/mol. The synthesized tetrazoles were screened for their in-vitro cytotoxic activity against epidermoid cancer cell line (A431) and colon cancer line (HCT116) with respect to normal skin fibroblast cell line (BJ-1) using MTT assay, and antimicrobial activity against the bacteria: K. pneumonia, S. aureus, and the fungi: Candida albicans, as well as their antioxidant activity using 2,2-diphenyl-1-picrylhydrazyl assay. In addition, the toxicity of tetrazole derivative was assessed by determination of their approximate lethal dose fifty (LD50), calculated via an oral administration to rats, through measurement of ALT and bilirubin levels in serum. The antitumor results can suggest that the potent tetrazole derivative namely, 3-(3,4-dimethoxyphenyl)-2-(1H-tetrazol-5-yl)acrylonitrile (4c) could be a potential drug against epidermoid carcinoma. The antioxidant results indicated to tetrazoles exhibited great antioxidant properties even at very low doses. A molecular dynamics simulation was performed for the synthesized compounds (ligands) to investigate their tendency for binding with the active sites of protein.

Design, synthesis and biological evaluation of novel indole-3-carboxylic acid derivatives with antihypertensive activity.

Molecular design, synthesis, in vitro and in vivo studies of novel derivatives of indole-3-carboxylic acid new series of angiotensin II receptor 1 antagonists is presented. Radioligand binding studies using [125I]-angiotensin II displayed that new derivatives of indole-3-carboxylic acid have a high nanomolar affinity for the angiotensin II receptor (AT1 subtype) on a par with the known pharmaceuticals such as losartan. Biological studies of synthesized compounds in spontaneously hypertensive rats have demonstrated that compounds can lower blood pressure when administered orally. Maximum the decrease in blood pressure was 48 mm Hg with oral administration of 10 mg/kg and antihypertensive effect was observed for 24 h, which is superior to losartan.

Tetrazole Diversification of Amino Acids and Peptides via Silver-Catalyzed Intermolecular Cycloaddition with Aryldiazonium Salts.

Selective structural modification of amino acids and peptides is a central strategy in organic chemistry, chemical biology but also in pharmacology and material science. In this context, the formation of tetrazole rings, known to possess significant therapeutic properties, would expand the chemical space of unnatural amino acids but has received less attention. In this study, we demonstrated that the classic unimolecular Wolff rearrangement of α-amino acid-derived diazoketones could be replaced by a faster intermolecular cycloaddition reaction with aryldiazonium salts under identical practical conditions. This strategy provides an efficient synthetic platform that could transform proteinogenic α-amino acids into a plethora of unprecedented tetrazole-decorated amino acid derivatives with preservation of the stereocenters. Density functional theory studies shed some light on the reaction mechanism and provided information regarding the origins of the chemo- and regioselectivity. Furthermore, this diazo-cycloaddition protocol was applied to construct tetrazole-modified peptidomimetics and drug-like amino acid derivatives.

Tetrazole-based inhibitors of the bacterial enzyme N-succinyl-l,l-2,6-diaminopimelic acid desuccinylase as potential antibiotics.

Based on a hit from a high-throughput screen, a series of phenyltetrazole amides was synthesized and assayed for inhibitory potency against DapE from Haemophilus influenzae (HiDapE). The inhibitory potency was modest but confirmed, with the most potent analog containing an aminothiazole moiety displaying an IC50 = 50.2 ± 5.0 µM. Docking reveals a potential binding mode wherein the amide carbonyl bridges both zinc atoms in the active site, and the tetrazole forms key hydrogen bonds with Arg330.

Optimization and SAR research at the benzoxazole and tetrazole rings of JNJ4796 as new anti-influenza A virus agents, part 2.

We have already reported the modification on the piperazine and phenyl rings of JNJ4796, a small-molecule fuse inhibitor targeting hemagglutinin (HA). In this study, we described the structure-activity relationship of the benzoxazole and tetrazole rings of JNJ4796. Many derivatives demonstrated good in vitro activity against IAV H1N1and Oseltamivir-resistant IAV H1N1 stains. Although compounds (R)-1e and (R)-1h exhibited excellent in vitro activity, high drug exposure level and low hERG inhibition, they displayed low oral efficacy. Excitedly, (R)-1a, a representative identified in our previous study, was found to show potent in vivo anti-IAV activity with the survival rates of 100%, 100% and 70% at 15, 5 and 1.67 mg/kg, respectively, comparable to JNJ4796. Currently, we are exploring different ways to ease its gastrointestinal response.

Design, Synthesis, Molecular Docking, ADMET, and Biological Studies of Some Novel 1,2,3-Triazole Linked Tetrazoles as Anticancer Agents.

BACKGROUND: 1,2,3-Triazole-tetrazoles have received substantial attention because of their unique bioisosteric properties and an extraordinarily broad spectrum of biological activity, making them interesting for the drug design, and synthesis of a delightful class of widely investigated heterocyclic compounds. To address major health concerns, it is consequently important to devote ongoing effort to the identification and development of New Chemical Entities (NCEs) as possible anticancer medicines. METHODS: We began our initial investigation of the reaction between 5-(azidomethyl)-1H-pyrrolo[ 2,3-b]pyridine and 1-phenyl substituted-5-(prop-2-yn-1-ylthio)-1 H-tetrazole under click chemistry to give the corresponding triazole precursors and screened for their cytotoxicity reported by variations in therapeutic actions of the parent molecule. All of the prepared scaffolds were characterized by proton, carbon resonance spectroscopy, IR, and mass spectral techniques. RESULTS: When tested for in vitro antitumor activity the prepared compounds 7e, 7h had a significant anticancer activity against human adenocarcinoma Hs766T cell line with IC50 = 5.33, 4.92 µg/mL and Hs460 cell line with IC50 = 4.82, 6.15 µg/mL respectively. Final scaffolds 7f, 7h, and 7j acquire the highest potential drug binding scores ΔG = -10.42, -8.80, -9.37 Kcal/, with amino acids residues Ala A:11 (2.195 A˚), Asp A:119 (1.991 A˚), Thr A:58 (1.890 A˚), Lys A:16 (1.253 A˚), Asp A:38 (2.013 A˚), Lys A:117 (2.046 A˚) respectively and process Lipinski's rule of five as good agents for oral bioavailability. CONCLUSION: The molecular framework for the synthesis of novel Aza indole 1,2,3-triazole scaffolds coupled to tetrazole core was discovered in our study and evaluated for their anticancer activity.

Functionalized Tetrazoles as Latent Active Esters in the Synthesis of Amide Bonds.

We report the use of N-2,4-dinitrophenyltetrazoles as latent active esters (LAEs) in the synthesis of amide bonds. Activating the tetrazole generates an HOBt-type active ester without the requirement for exogenous coupling agents. The methodology was widely applicable to a range of substrates, with up to quantitative yields obtained. The versatility and functional group tolerance were exemplified with the one-step synthesis of various pharmaceutical agents and the N-acylation of resin-bound peptides.

SnAr Reactions of 2,4-Diazidopyrido[3,2-d]pyrimidine and Azide-Tetrazole Equilibrium Studies of the Obtained 5-Substituted Tetrazolo[1,5-a]pyrido[2,3-e]pyrimidines.

A straightforward method for the synthesis of 5-substituted tetrazolo[1,5-a]pyrido[2,3-e]pyrimidines from 2,4-diazidopyrido[3,2-d]pyrimidine in SnAr reactions with N-, O-, and S- nucleophiles has been developed. The various N- and S-substituted products were obtained with yields from 47% to 98%, but the substitution with O-nucleophiles gave lower yields (20-32%). Furthermore, the fused tetrazolo[1,5-a]pyrimidine derivatives can be regarded as 2-azidopyrimidines and functionalized in copper(I)-catalyzed azide-alkyne dipolar cycloaddition (CuAAC) and Staudinger reactions due to the presence of a sufficient concentration of the reactive azide tautomer in solution. In total, seven products were fully characterized by their single crystal X-ray studies, while five of them were representatives of the tetrazolo[1,5-a]pyrido[2,3-e]pyrimidine heterocyclic system. Equilibrium constants and thermodynamic values were determined using variable temperature 1H NMR and are in agreement of favoring the tetrazole tautomeric form (ΔG298 = -3.33 to -7.52 (kJ/mol), ΔH = -19.92 to -48.02 (kJ/mol) and ΔS = -43.74 to -143.27 (J/mol·K)). The key starting material 2,4-diazidopyrido[3,2-d]pyrimidine presents a high degree of tautomerization in different solvents.