Overview of Small Molecules as Fluorescent Probes of Mycobacterium tuberculosis.

Tuberculosis (TB) remains one of the leading infectious causes of death worldwide. Detecting and precisely quantifying viable Mycobacterium tuberculosis (M. tuberculosis) is crucial for comprehending mycobacterial pathogenicity; the progression and outcomes of tuberculosis; and the action, efficacy, and resistance of drugs. Fluorescent probes have emerged as indispensable tools for studying the intricate structure and dynamic interactions of M. tuberculosis with its host environment. This minireview underscores the significance of small molecules as fluorescent probes in advancing our understanding of mycobacterial biology and highlights their potential for guiding the development of novel therapeutic interventions against tuberculosis.

In vitro Modified Release Studies on Melatoninergic Fluorinated Phenylalkylamides: Circumventing their Lipophilicity for Oral Administration.

INTRODUCTION: In an attempt to circumvent the lipophilicity burden for the oral administration of new potent synthetic melatoninergic fluorine-substituted methoxyphenylalkyl amides, we conducted in vitro modified release studies using carefully selected matrix tablets' biopolymeric materials in different ratios. METHODS: In particular, we sought to attain release profiles of these analogues similar to that of the parent compound, the chronobiotic hormone Melatonin (MLT), and also of the commercially available drug, Circadin®. RESULTS: It was found that some of these systems, albeit being more lipophilic than MLT, mimic the in vitro release patterns of melatonin and Circadin®. CONCLUSION: Moreover, a number of these derivatives were proven suitable for dealing with sleep onset problems, whilst others for dealing with combined sleep onset/sleep maintenance dysfunctions.

Potent Lipophilic Melatoninergic x-fluoro-y-methoxy Substituted Phenylalkylamides: Molecular Dynamics Calculations and in vitro Modified Release in Aqueous Media from Tablet Formulations.

INTRODUCTION: We report herein on the design and development of matrix tablets containing potent synthetic melatonin (MLT) receptor analogues, the x-fluoro-y-methoxy substitiuted phenylalkylamides (compounds I-IV), the preparation and melatoninergic potency of which was recently communicated. > Methods: The presence of the fluorine atom in compounds I-IV, besides not affecting their binding affinity, compared to the pineal hormone melatonin, it also slows down their metabolism, which is a major drawback of MLT. However, as fluorine increases the lipophilicity, solid pharmaceutical formulations of I-IV, involving the appropriate biopolymers for their modified release in aqueous media, were developed in the context of the present work. > Results: The release profile of analogues I-IV was found to be similar to that of MLT and also of the commercially available drug, Circadin®. Some of these systems are suitable for dealing with sleep onset problems, whilst others for dealing with combined sleep onset/sleep maintenance problems. > Conclusion: Apart from the nature and relevant content of the formulants used, this bimodal release profile of the new analogues depends, to a large extent, on the diverse structural arrangement of their side chains in space, as nicely demonstrated by the molecular dynamics calculations, conducted in the context of this study. >.

Synthesis and Testing of Analogs of the Tuberculosis Drug Candidate SQ109 against Bacteria and Protozoa: Identification of Lead Compounds against Mycobacterium abscessus and Malaria Parasites.

SQ109 is a tuberculosis drug candidate that has high potency against Mycobacterium tuberculosis and is thought to function at least in part by blocking cell wall biosynthesis by inhibiting the MmpL3 transporter. It also has activity against bacteria and protozoan parasites that lack MmpL3, where it can act as an uncoupler, targeting lipid membranes and Ca2+ homeostasis. Here, we synthesized 18 analogs of SQ109 and tested them against M. smegmatis, M. tuberculosis, M. abscessus, Bacillus subtilis, and Escherichia coli, as well as against the protozoan parasites Trypanosoma brucei, T. cruzi, Leishmania donovani, L. mexicana, and Plasmodium falciparum. Activity against the mycobacteria was generally less than with SQ109 and was reduced by increasing the size of the alkyl adduct, but two analogs were ∼4-8-fold more active than SQ109 against M. abscessus, including a highly drug-resistant strain harboring an A309P mutation in MmpL3. There was also better activity than found with SQ109 with other bacteria and protozoa. Of particular interest, we found that the adamantyl C-2 ethyl, butyl, phenyl, and benzyl analogs had 4-10× increased activity against P. falciparum asexual blood stages, together with low toxicity to a human HepG2 cell line, making them of interest as new antimalarial drug leads. We also used surface plasmon resonance to investigate the binding of inhibitors to MmpL3 and differential scanning calorimetry to investigate binding to lipid membranes. There was no correlation between MmpL3 binding and M. tuberculosis or M. smegmatis cell activity, suggesting that MmpL3 is not a major target in mycobacteria. However, some of the more active species decreased lipid phase transition temperatures, indicating increased accumulation in membranes, which is expected to lead to enhanced uncoupler activity.

Mapping the Melatonin Receptor. 8. Selective MT2 Agonists Derived from 5,6-Dihydroindolo[2,1-a]isoquinolines and Related Systems.

A series of substituted indolo[2,1-a]isoquinolines and indolo[1,2-a]benzoxazines have been prepared, as melatonin analogues, to investigate the nature of the binding site of the melatonin receptor. Agonist and antagonist potency of all the analogues was measured using the [35S]GTPγS binding assay protocol. The binding affinity of the analogues were measured by competition binding studies against the human MT1 (hMT1) and MT2 (hMT2) receptors stably transfected in Chinese Hamster Ovarian (CHO) cells, using 2-[125 I]-iodomelatonin, as a ligand. N-Acetyl 2-(10-methoxy-5,6-dihydroindolo[2,1-a]isoquinolin-12-yl)propyl-1-amine (12 a) binds strongly to both the hMT1 and hMT2 receptors, and shows a preference for the hMT2, as does its propanamido counterpart 12 b. The introduction of two methyl groups into their side chain, analogues 15 a and 15 b, leads to antagonism, in the case of the former, and drastically diminishes its hMT1 binding; an analogous profile is seen for 15 b, which, however, is a partial agonist. Introduction of chlorine or methoxy groups into ring 4 gives compounds, that are weakly binding, with a preference for MT2. Substitution of oxygen for carbon at position 5 gives the indolo[1,2-c]benzoxazines 33, 36 a and b, that bind strongly to the human receptors, 33, 36 b being potent agonists at the melatonin receptors, but do not discriminate between hMT1 and hMT2.

Evidence for spontaneous cannabinoid withdrawal in mice.

Although the behavioral effects of acute and chronic exposure to cannabinoids have been extensively studied in mice, spontaneous withdrawal following exposure to cannabinoids has not been well characterized in this species. To address this issue, different groups of mice were treated for 5 days with saline, 20-36 mg/kg/day of the CB partial agonist Δ9-tetrahydrocannabinol (Δ9-THC), or 0.06-0.1 mg/kg/day of the CB high-efficacy agonist AM2389. Initial studies assessed changes in observable behavior (paw tremors) that were scored from the recordings taken at 4 or 24 h after the last injection. Subsequently, radiotelemetry was used to continuously measure body temperature and locomotor activity before (baseline), during, and after the 5-day dosing regimens. Results show that increases in paw tremors occurred following 5-day exposure to AM2389 or Δ9-THC. In telemetry studies, acute AM2389 or THC decreased both temperature and activity. Rapid tolerance occurred to the hypothermic effects of the cannabinoids, whereas locomotor activity continued to be suppressed following each drug injection. In contrast, increases in locomotor activity were evident 12-72 h after discontinuing daily injections of either 0.06 or 0.1 mg/kg/day AM2389. Increases in locomotor activity were also noted in mice treated daily with 30 or 36, but not 20 mg/kg/day Δ9-THC; these effects were smaller and appeared later than effects seen in AM2389-treated mice. These results indicate that the discontinuation of daily treatment with a CB high-efficacy agonist will yield evidence of spontaneous withdrawal that may reflect prior dependence, and that the degree of cannabinoid dependence may vary in relation to the dose or efficacy of the agonist injected daily.

Improved cyclobutyl nabilone analogs as potent CB1 receptor agonists.

In earlier work, we explored the SAR for the C3 side chain pharmacophore in the hexahydrocannabinol template represented by the drug nabilone, which resulted in the development of AM2389. In an effort for further optimization, we have merged features of nabilone and AM2389 and explored the C3 side chain with varying chain lengths and terminal substitutions. Of the compounds described here, a nabilone analog, AM8936, with the C6'-cyano-substituted side chain, was identified as the most successful analog capable of serving as a potential candidate for further development and a valuable tool for further in vivo studies. AM8936 behaved as a balanced and potent CB1 agonist in functional assays and was a potent and efficacious CB1 agonist in vivo. Our SAR studies are highlighted with the docking of AM8936 on the crystal structure of the hCB1 receptor.

An Overview on Target-Based Drug Design against Kinetoplastid Protozoan Infections: Human African Trypanosomiasis, Chagas Disease and Leishmaniases.

The protozoan diseases Human African Trypanosomiasis (HAT), Chagas disease (CD), and leishmaniases span worldwide and therefore their impact is a universal concern. The present regimen against kinetoplastid protozoan infections is poor and insufficient. Target-based design expands the horizon of drug design and development and offers novel chemical entities and potential drug candidates to the therapeutic arsenal against the aforementioned neglected diseases. In this review, we report the most promising targets of the main kinetoplastid parasites, as well as their corresponding inhibitors. This overview is part of the Special Issue, entitled "Advances of Medicinal Chemistry against Kinetoplastid Protozoa (Trypanosoma brucei, Trypanosoma cruzi and Leishmania spp.) Infections: Drug Design, Synthesis and Pharmacology".

Pineal hormone melatonin as an adjuvant treatment for COVID­19 (Review).

The beneficial properties of the pineal hormone, melatonin, as a neuroprotective and cardioprotective agent, have been previously identified. Furthermore, melatonin plays essential roles in biological rhythms resynchronization, sleep initiation/maintenance and metabolic, ocular, rheumatological diseases. In addition to these functions, melatonin is known to exert immunomodulation, anti­inflammatory and anti­oxidative effects. Due to these properties, coupled with its non­toxic nature, melatonin has been suggested to limit viral infections; however, melatonin cannot be classified as a viricidal drug. In addition, the recent increase in the number of clinical trials on melatonin's role, as an adjuvant treatment for COVID­19, has resurged the interest of the scientific community in this hormone. The present short review aimed to improve the understanding of the antiviral/anti­COVID­19 profile of melatonin and the clinical trials that have recently been conducted, with respect to its co­administration in treating individuals with COVID­19.

Biophysical Evaluation and In Vitro Controlled Release of Two Isomeric Adamantane Phenylalkylamines with Antiproliferative/Anticancer and Analgesic Activity.

The aqueous dissolution profile of the isomeric synthetic adamantane phenylalkylamine hydrochlorides I and II was probed. These adducts have shown significant antiproliferative/anticancer activity associated with an analgesic profile against neuropathic pain. They are both devoid of toxic effects and show appreciable enzymatic human plasma stability. The structures of these two compounds have been elucidated using 2D NMR experiments, which were used to study their predominant conformations. Compound II's scaffold appeared more flexible, as shown by the NOE spatial interactions between the alkyl bridge chain, the aromatic rings, and the adamantane nucleus. Conversely, compound I appeared very rigid, as it did not share significant NOEs between the aforementioned structural segments. MD simulations confirmed the NOE results. The aqueous dissolution profile of both molecules fits well with their minimum energy conformers' features, which stem from the NOE data; this was nicely demonstrated, especially in the case of compound II.

Chemical Probes for Blocking of Influenza A M2 Wild-type and S31N Channels.

We report on using the synthetic aminoadamantane-CH2-aryl derivatives 1-6 as sensitive probes for blocking M2 S31N and influenza A virus (IAV) M2 wild-type (WT) channels as well as virus replication in cell culture. The binding kinetics measured using electrophysiology (EP) for M2 S31N channel are very dependent on the length between the adamantane moiety and the first ring of the aryl headgroup realized in 2 and 3 and the girth and length of the adamantane adduct realized in 4 and 5. Study of 1-6 shows that, according to molecular dynamics (MD) simulations and molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) calculations, all bind in the M2 S31N channel with the adamantyl group positioned between V27 and G34 and the aryl group projecting out of the channel with the phenyl (or isoxazole in 6) embedded in the V27 cluster. In this outward binding configuration, an elongation of the ligand by only one methylene in rimantadine 2 or using diamantane or triamantane instead of adamantane in 4 and 5, respectively, causes incomplete entry and facilitates exit, abolishing effective block compared to the amantadine derivatives 1 and 6. In the active M2 S31N blockers 1 and 6, the phenyl and isoxazolyl head groups achieve a deeper binding position and high kon/low koff and high kon/high koff rate constants, compared to inactive 2-5, which have much lower kon and higher koff. Compounds 1-5 block the M2 WT channel by binding in the longer area from V27-H37, in the inward orientation, with high kon and low koff rate constants. Infection of cell cultures by influenza virus containing M2 WT or M2 S31N is inhibited by 1-5 or 1-4 and 6, respectively. While 1 and 6 block infection through the M2 block mechanism in the S31N variant, 2-4 may block M2 S31N virus replication in cell culture through the lysosomotropic effect, just as chloroquine is thought to inhibit SARS-CoV-2 infection.

Repurposing current therapeutic regimens against SARS-CoV-2 (Review).

The recent coronavirus outbreak has spread worldwide, with the exception of Antarctica, causing serious social and economic disruption. All disciplines of the science community are driven to confront the impact of the COVID-19 pandemic, as currently, there is neither prophylactic nor therapeutic treatments available. Due to the urgency of the situation, various research strategies are ongoing, in order to evaluate the therapeutic efficacy of repurposed and experimental drugs. The present review presents the most promising repurposed regimens, which may be used for the treatment of COVID-19. The drugs/bioactive substances presented herein belong to diverse therapeutic classes, including antimalarial, cardioprotective, angiotensin-converting enzyme 2 inhibitors, antiviral, anti-inflammatory and antiparasitic drugs. Therapeutic perspectives of vaccination and passive immunization are also reviewed.

Multicomponent Reaction of Aldehydes, Amines and Oxalacetate Analogues Leading to Biologically Attractive Pyrrole Derivatives.

Pyrrole is a very important pharmacophoric moiety. It has been widely incorporated into the skeleton of antitumor, anti-inflammatory, antibacterial, antioxidant and antifungal active substances. Access to this key heterocycle by diverse routes is particularly attractive in terms of chemistry, and also from the environmental point of view. The present minireview summarizes the reported methods for the preparation of highly substituted pyrrole derivatives based on the one-pot multicomponent reaction of aldehydes, primary amines, and oxalacetate analogues as well as their biology.

Synthesis and evaluation of novel 2,4-disubstituted arylthiazoles against T. brucei.

The design, synthesis and pharmacological evaluation of the 4-substituted-2-[3-(adamant-1-yl)-4-fluorophenyl]thiazoles 1a-j, the 4-substituted-2-[4-(adamant-1-yl)phenyl]thiazoles 2a-h, the 2-substituted-4-[4-(adamant-1-yl)phenyl]thiazoles 3a-e, the N-substituted 2-phenylthiazol-4-ethylamides 4a, b and the N-substituted 4-phenylthiazol-2-ethylamides 4c, d is described. Compounds 1a and 2a exhibit trypanocidal activity in the range of IC50 = 0.42 µM and IC50 = 0.80 µM, respectively. Both of these derivatives bear a lipophilic end, which consists of a 4-(1-adamantyl) phenyl or a 3-(1-adamantyl)phenyl moiety, a 1,3-thiazole ring and a functional end, which comprises of an alkylamine and can be considered as promising candidates for the treatment of Trypanosoma brucei infections.

Fluorine substituted methoxyphenylalkyl amides as potent melatonin receptor agonists.

A series of fluorine substituted methoxyphenylalkyl amides were prepared with different orientations of the fluorine and methoxy groups with respect to the alkylamide side chain and with alkyl sides of differing lengths (n = 1-3). ß-Dimethyl and α-methyl derivatives were also synthesised. The compounds were tested as melatonin agonists and antagonists using the pigment aggregation of Xenopus melanophores as the biological assay. A number of these compounds were potent melatonin agonists, the potency depending on the length of the alkyl chain, the orientation of the methoxy and fluorine substituents, the amide chain length and, for the ethyl side-chain analogues, the presence of ß-substituents.

Synthesis and Evaluation of Nifurtimox-Adamantane Adducts with Trypanocidal Activity.

The synthesis and pharmacological evaluation of C1-substituted adamantane hydrazones, their C2-substituted isomers, and C1-substituted adamantane furanoic carboxamides is described. These new adamantane derivatives exhibited an interesting pharmacological profile in terms of trypanocidal activity and selectivity. The most active adduct with the best selectivity in this study was found to be the phenylacetoxy hydrazone 1 b (2-[4-(tricyclo[3.3.1.13,7 ]dec-1-yl)phenyl]-N'-[(5-nitrofuran-2-yl)methylene]acetohydrazide; EC50 =11±0.9 nm, SITb =770).

Bone tumours around the elbow: a rare entity.

Bone tumours around the elbow are rare. Even nowadays diagnostic dilemmas and delays are common. During recent decades the management and prognosis of patients with elbow bone tumours has improved significantly.Benign tumours can be treated using minimally invasive procedures, whereas malignant ones require a multidisciplinary team approach based on an adjuvant therapeutic regimen of chemotherapy, radiotherapy and limb salvage procedures.This article reviews the most commonly encountered elbow bone tumours and their management. Cite this article: EFORT Open Rev 2019;4:133-142. DOI: 10.1302/2058-5241.4.180086.

Synthesis of diphenoxyadamantane alkylamines with pharmacological interest.

In this work, the synthesis and the pharmacological evaluation of diphenoxyadamantane alkylamines Ia-f and IIa-f is described. The new diphenoxy-substituted adamantanes share structural features present in trypanocidal and antitubercular agents. 1-Methylpiperazine derivative Ia is the most potent against T. brucei compound, whilst its hexylamine congener IIf exhibits a significant antimycobacterial activity.

Insights in Organometallic Synthesis of Various Adamantane Derivatives with Sigma Receptor-Binding Affinity and Antiproliferative/Anticancer Activity.

Organometallic reactions, such as those involving Grignard and organocadmium reagents, are very useful but require prudent laboratory skills. In many papers related to the medicinal chemistry of adamantane derivatives with sigma receptor (σR)-binding affinity and antiproliferative/anticancer activity, organometallics play a crucial role in the synthetic pathways. In this work, the experimental procedures utilizing Grignard and organocadmium reagents are presented in detail, because these techniques are not analyzed and are important in the rational drug design.

Sigma Receptor (σR) Ligands with Antiproliferative and Anticancer Activity.

Sigma receptor (σR) ligands have proven to be useful as cancer diagnostics and anticancer therapeutics and their ligands have been developed as molecular probes in oncology. Moreover, various σR ligands generate cancer cell death in vitro and in vivo. These σR ligands have exhibited promising results against numerous human and rodent cancers and are investigated under preclinical and clinical study trials, indicating a new category of drugs in cancer therapy.