Macrocyclic peptidomimetics with antimicrobial activity: synthesis, bioassay, and molecular modeling studies

Peptidomimetics based on ammonium decasubstituted pillar[5]arenes: Influence of the alpha-amino acid residue nature on cholinesterase inhibition

Cholinesterase inhibitors are a group of medicines that are widely used for the treatment of cognitive impairments accompanying Alzheimer's disease as well as for the treatment of pathological muscle weaknesses syndromes such as myasthenia gravis. The search for novel non-toxic and effective cholinesterase inhibitors for creating neuroprotective and neurotransmitter agents is an urgent interdisciplinary problem. For the first time, the application of water-soluble pillar[5]arenes containing amino acid residues as effective cholinesterase inhibitors was shown. The influence of the nature of aliphatic and aromatic alpha-amino acid residues (glycine, l-alanine, l-phenylalanine and l-tryptophan) on self-assembly, aggregate's stability, cytotoxicity on A549 and LEK cells and cholinesterase inhibition was studied. It was found that the studied compounds with aliphatic amino acid residues showed a low inhibitory ability against cholinesterases. It was established that the pillar[5]arene containing fragments of l-phenylalanine is the most promising inhibitor of butyrylcholinesterase (IC50 = 0.32 ± 0.01 μM), the pillar[5]arene with l-tryptophan residues is the most promising inhibitor of acetylcholinesterase (IC50 = 0.32 ± 0.01 μM). This study has shown a possible application of peptidomimetics based on pillar[5]arenes to inhibit cholinesterase, as well as control the binding affinity to a particular enzyme in a structure-dependent manner.

The Anti-Amoebic Activity of a Peptidomimetic against Acanthamoeba castellanii

Acanthamoeba is a free-living protozoan known to cause keratitis most commonly, especially among contact lens wearers. Treatment of Acanthamoeba keratitis is challenging as Acanthamoeba can encyst from the active form, a trophozoite, into a hibernating cyst that is refractory to antibiotics and difficult to kill; therefore, there is a need for more effective anti-amoebic strategies. In this study, we have evaluated the anti-amoebic activity of the antimicrobial peptide mimic RK-758 against Acanthamoeba castellanii. RK-758 peptidomimetic was subjected to biological assays to investigate its amoebicidal, amoebistatic, anti-encystation, and anti-excystation effects on A. castellanii. The anti-amoebic activity of the peptide mimic RK-758 was compared with chlorhexidine against the Acanthamoeba castellanii ATCC30868 and Acanthamoeba castellanii 044 (a clinical strain) with the concentrations of both ranging from 125 µM down to 7.81 µM. All experiments were performed in duplicate with three independent replicates. The data were represented as mean ± SE and analysed using a two-sample t-test and two-tailed distributions. A p < 0.05 was considered statistically significant. The peptidomimetic RK-758 had anti-Acanthamoeba activity against both trophozoites and cysts in a dose-dependent manner. The RK-758 had amoebicidal and growth inhibitory activities of ≥50% at a concentration between 125 µM and 15.6 µM against the trophozoites of both Acanthamoeba strains. Inhibitory effects on the cyst formation and trophozoite re-emergence from cysts were noted at similar concentrations. Chlorhexidine had 50% activity at 7.81 µM and above against the trophozoites and cysts of both strains. In the haemolysis assay, the RK-758 lysed horse RBCs at concentrations greater than 50 µM whereas lysis occurred at concentrations greater than 125 µM for the chlorhexidine. The peptidomimetic RK-758, therefore, has activity against both the trophozoite and cyst forms of Acanthamoeba and has the potential to be further developed as an anti-microbial agent against Acanthamoeba. RK-758 may also have use as an anti-amoebic disinfectant in contact lens solutions.

Pharmacological Activities of Aminophenoxazinones

Aminophenoxazinones are degradation products resulting from the metabolism of different plant species, which comprise a family of natural products well known for their pharmacological activities. This review provides an overview of the pharmacological properties and applications proved by these compounds and their structural derivatives during 2000-2021. The bibliography was selected according to our purpose from the references obtained in a SciFinder database search for the Phx-3 structure (the base molecule of the aminophenoxazinones). Compounds Phx-1 and Phx-3 are among the most studied, especially as anticancer drugs for the treatment of gastric and colon cancer, glioblastoma and melanoma, among others types of relevant cancers. The main information available in the literature about their mechanisms is also described. Similarly, antibacterial, antifungal, antiviral and antiparasitic activities are presented, including species related directly or indirectly to significant diseases. Therefore, we present diverse compounds based on aminophenoxazinones with high potential as drugs, considering their levels of activity and few adverse effects.

Novel Dipeptides Bearing Sulfonamide as Antimalarial and Antitrypanosomal agents: Synthesis and Molecular Docking

OBJECTIVE

Currently, there is a problem of ineffective chemotherapy to trypanosomiasis and the increasing emergence of malarial drug-resistant parasites. This research aimed to develop new dipeptide-sulfonamides as antiprotozoal agents.

BACKGROUND

Protozoan parasites cause severe diseases, with human African trypanosomaisis (HAT) and malaria leading the list. The noted deficiencies of existing antitrypanosomal drugs and the worldwide resurgence of malaria, accompanied by the springing up of widespread drug-resistant protozoan parasites, represent a huge challenge in infectious disease treatment in tropical regions.

METHODS

In order to discover new antiprotozoal agents, ten novel p-nitrobenzenesulphonamide derivatives incorporating dipeptide moiety were synthesized by the condensation reaction of 3-methyl-2-(4-nitrophenylsulphonamido)pentanoic acid (6) with substituted acetamides (4a-j) using peptide coupling reagents, characterized using 1H and 13C NMR, FTIR, HRMS, and investigated for their antimalarial and antitrypanosomal activities in vivo employing standard methods.

RESULTS

At 100 mg/kg body weight, N-(2-(2,6-dimethylphenylamino)-2-oxoethyl)-3-methyl-2-(4-nitrophenylsulfonamido)pentanamide showed the highest activity by inhibiting P. berghei parasite by 79.89%, which was comparable with the standard drug (artemether-lumefantrine 79.77%). In the antitrypanosomal study, N-(2-(4-chlorophenylamino)-2-oxoethyl)-3-methyl-2-(4-nitrophenylsulfonamido)pentanamide, N-(2-(4-fluorophenylamino)-2-oxoethyl)-3-methyl-2-(4-nitrophenylsulfonamido)pentanamide, and N-(2-(3-chlorophenylamino)-2-oxoethyl)-3-methyl-2-(4-nitrophenylsulfonamido)pentanamide were most potent in clearing Trypanosome brucei in mice. However, they were less active than the standard drug (diminazene aceturate). Molecular docking results demonstrated good binding affinity among the reported derivatives and target proteins in the active place of the protein. The outcome of haematological analysis and liver and kidney function tests showed that the new compounds had no adverse effect on the blood and organs.

CONCLUSIONS

The results of this research showed that the new compounds demonstrated interesting antitrypanosomal and antimalarial potentials. However, further research should be carried out on the synthesized derivatives as promising drug candidates for trypanosomiasis and malaria.

Synthesis, molecular docking, antiplasmodial and antioxidant activities of new sulfonamido-pepetide derivatives

Twenty-three new series of toluene-sulfonamide dipeptide derivatives were synthesized and screened for antiplasmodial and antioxidant potencies. Many of the derivatives were active against Plasmodium falciparum with IC50 ranging from 3.20 - 9.10 μM. The ability of compounds 7h, 7m and 7n (IC50 of 7.53, 7.21 and 6.01 μg/mL respectively) to scavenge DPPH free radicals were comparable to that of ascorbic acid. Additionally, molecular docking disclosed that four compounds exhibited theoretical inhibition constant at submicromolar concentrations (K i = 0.72, 0.75, 0.57, and 0.53 μM respectively) compare to the reference ligand (a pyrazole sulfonamide; K i = 0.01 μM). Overall, some of the derivatives possess antimalarial property as well as the ability to inhibit oxidative stress in malaria pathophysiology; and hence, are good candidates for further antimalarial drug research.

Synthesis, pharmacological profile and 2D-QSAR studies of curcumin-amino acid conjugates as potential drug candidates

A series of curcumin bis-conjugates 3a-q, 5a-k and 6a-k were synthesized in good yields utilizing an optimized reaction condition. We explored the effect of different amino acids and protecting groups on biological activities of curcumin. The conjugates were screened for anti-inflammatory, analgesic and antimicrobial properties. Some of the conjugates showed promising biological observations with a potency comparable with the standard references. The variations in biological properties concerning different amino acids and protecting groups are interesting observations. Effects of the synthesized conjugates on splenocytes and the production of nitric oxide by lipopolysaccharide-stimulated peritoneal macrophages are correlated with the observed anti-inflammatory properties. We have also established the safety profile of the most active conjugates. Robust 2D-QSAR studies supported and validated biological data.

Synthesis and human carbonic anhydrase I, II, VA, and XII inhibition with novel amino acid-sulphonamide conjugates

A series of amino acid-sulphonamide conjugates was prepared through benzotriazole mediated coupling reactions and characterised by ¹H-NMR, ¹³C-NMR, MS, and FTIR spectroscopic techniques as well as elemental analysis. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was determined against four human (h) isoforms, hCA I, hCA II, hCA VA, and hCA XII. Most of the synthesised compounds showed effective in vitro CA inhibitory properties. The new amino acid-sulphonamide conjugates showed potent inhibitory activity against hCA II, some of them at subnanomolar levels, exhibiting more effective inhibitory activity compared to the standard drug acetazolamide. Some of these sulphonamides were also found to be effective inhibitors of hCA I, hCA VA, and hCA XII, with activity from the low to high nanomolar range.

Synthesis carbonic anhydrase enzyme inhibition and antioxidant activity of novel benzothiazole derivatives incorporating glycine, methionine, alanine, and phenylalanine moieties

Thirteen novel benzothiazole derivatives incorporating glycine, methionine, alanine, and phenylalanine were synthesised by facile acylation reactions through benzotriazole or DCC mediated reactions and their structures were identified by 1H-NMR, 13C-NMR, and FT-IR spectroscopic techniques and elemental analysis. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was assessed against four human (h) isoforms, hCA I, hCA II, hCA V, and hCA XIII. Some of the synthesised compounds showed good in vitro carbonic anhydrase inhibitory properties, with inhibition constants in the micromolar level. The new amino acid benzothiazole conjugates found to be more effective against hCA V and hCA II inhibition. In vitro antioxidant activities of the novel compounds were determined by DPPH method. Most of the synthesised compounds showed moderate to low antioxidant activities compared to the control antioxidant compounds (BHA and α-tocopherol).

Synthesis, human topoisomerase IIα inhibitory properties and molecular modeling studies of anti-proliferative curcumin mimics

Piperidinecarboxamides (curcumin mimics) show promising anti-proliferative properties against HCT116 (colon), MCF7 (breast) and A431 (squamous skin) carcinoma cell lines with potency higher than that of 5-fluorouracil.

Synthesis and carbonic anhydrase inhibitory properties of novel 4-(2-aminoethyl)benzenesulfonamide-dipeptide conjugates

Thirty novel sulfonamide derivatives incorporating dipeptide were synthesized by facile acylation through benzotriazole mediated reactions and their structures were identified by ¹H NMR, ¹³C NMR, MS and FT-IR spectroscopic techniques and elemental analysis. The carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activity of the new compounds was assessed against four human (h) isoforms, hCA I, hCA II, hCA IV and hCA XII. Most of the synthesized compounds showed excellent in vitro carbonic anhydrase inhibitory properties comparable to those of the clinically used drug acetazolamide (AAZ). The new unprotected dipeptide-sulfonamide conjugates showed very effective inhibitory activity, in the low nanomolar range against II and XII, being less effective as hCA I and IV inhibitors. Four of the thirty compounds also showed strong inhibitory activity against hCA XII compared to AAZ.

Synthesis & molecular modeling studies of bronchodilatory active indole–pyridine conjugates

Aim: Synthesis of novel bronchodilatory active indole–pyridine conjugates. Results/methodology: Indole–pyridine conjugates (6a–n, 8a–i and 10a–c) were synthesized in a facile pathway through reaction of 2-[(1-alkyl-1H-indol-3-yl)methylene]malononitriles 4a,b with the corresponding ketone-containing compounds (5a–f, 7a–c and 9a,b) in the presence of sodium alkoxide. Single (6l, 8 g) and powder (6k, 8d) x-ray studies supported the structures. Results: Histamine precontracted isolated tracheal rings of guinea pig exhibited the potent bronchodilation properties of 6c (about double-fold potency relative to the standard reference, theophylline). Some of the synthesized conjugates (8d, 6c, 6f and 6e) revealed promising reduction of IL-8 production during lipopolysaccharide-induced airway inflammatory bioassay. Computational studies (3D pharmacophore, 2D-QSAR ‘quantitative structure–activity relationship’) showed high approximations to the bronchodilation properties and explained the parameters controlling biological observations.

Identification of some novel xanthine-based derivatives with bronchodilator activity

AIM

The discovery of new bronchodilators with higher efficacy than theophylline is an important issue for asthmatic patients.

MATERIALS & METHODS

Theophylline 2, 8-bromotheophylline 4 and theobromine 6 were reacted with different 2/3-chloro-N-phenylacetamides 1a-d or their propanamide analogs 1e-g to obtain 3a-g, 5a-g and 7a-g, respectively. The target compounds were screened for their in vitro bronchodilator activity using isolated guinea pig tracheal rings precontracted with histamine and compared with their precursors.

RESULTS

Many compounds exhibited promising activity especially 3d, 3f, 5d, 7d and 7e. 2D-QSAR study resulted in a significant model (N = 24, n = 5, R ² = 0.848, R ²cvOO = 0.748, R ²cvMO = 0.745, F = 21.215, s ² = 0.0002) using CODESSA-Pro software.

CONCLUSION

These compounds can be considered as promising hits for potent bronchodilators that may be useful for further investigations. [Formula: see text].

Advances in Development of Antimicrobial Peptidomimetics as Potential Drugs

The rapid emergence of multidrug-resistant pathogens has evolved into a global health problem as current treatment options are failing for infections caused by pan-resistant bacteria. Hence, novel antibiotics are in high demand, and for this reason antimicrobial peptides (AMPs) have attracted considerable interest, since they often show broad-spectrum activity, fast killing and high cell selectivity. However, the therapeutic potential of natural AMPs is limited by their short plasma half-life. Antimicrobial peptidomimetics mimic the structure and biological activity of AMPs, but display extended stability in the presence of biological matrices. In the present review, focus is on the developments reported in the last decade with respect to their design, synthesis, antimicrobial activity, cytotoxic side effects as well as their potential applications as anti-infective agents. Specifically, only peptidomimetics with a modular structure of residues connected via amide linkages will be discussed. These comprise the classes of α-peptoids (N-alkylated glycine oligomers), β-peptoids (N-alkylated β-alanine oligomers), β³-peptides, α/β³-peptides, α-peptide/β-peptoid hybrids, α/γ N-acylated N-aminoethylpeptides (AApeptides), and oligoacyllysines (OAKs). Such peptidomimetics are of particular interest due to their potent antimicrobial activity, versatile design, and convenient optimization via assembly by standard solid-phase procedures.

Synthesis, molecular modeling studies and bronchodilation properties of nicotinonitrile containing-compounds

Facile synthetic pathway for nicotinonitriles 5a‒o, 7a‒i was demonstrated through reaction of ketones 4a‒k, 6a‒f with ylidenemalononitrile 3 in the presence of sodium alkoxide. Meanwhile, nucleophilic attack of amines on 2-bromonicotinonitrile 9 (obtained through reaction of propenone 8 with malononitrile, followed by bromination with bromine in acetic acid) afforded 3-pyridinecarbonitriles 11a‒d. Single crystal X-ray of compound 7i reveals the monoclinic space group C2/c with 8 molecules per unit cell. Optimized structure of 7i [DFT/B3LYP, 6-31G(d,p)] shows close correlations to that of X-ray study. Compound 5l seems superior among all the synthesized analogues exhibiting bronchodilation properties about three folds potency compared to theophylline (standard reference) through pre-contracted tracheal rings with histamine standard method. Also compound 5a reveals promising observations (about two folds potency of the standard reference). Molecular modeling studies (3D-pharmacophore and 2D-QSAR) supported the observed biological properties.

Microwave-Assisted Syntheses of Bioactive Seven-Membered, Macro-Sized Heterocycles and Their Fused Derivatives

This review describes the recent advances in the microwave-assisted synthesis of 7-membered and larger heterocyclic compounds. Several types of reaction for the cyclization step are discussed: Ring Closing Metathesis (RCM), Heck and Sonogashira reactions, Suzuki-Miyaura cross-coupling, dipolar cycloadditions, multi-component reactions (Ugi, Passerini), etc. Green syntheses and solvent-free procedures have been introduced whenever possible. The syntheses discussed herein have been selected to illustrate the huge potential of microwave in the synthesis of highly functionalized molecules with potential therapeutic applications, in high yields, enhanced reaction rates and increased chemoselectivity, compared to conventional methods. More than 100 references from the recent literature are listed in this review.

Rational design, synthesis and 2D-QSAR studies of antiproliferative tropane-based compounds

Novel tropane-based compounds were synthesized exhibiting antiproliferative properties against HepG2 and MCF7 carcinoma cell lines.

Synthesis, X-ray powder diffraction and DFT calculations of vasorelaxant active 3-(arylmethylidene)pyrrolidine-2,5-diones

Two 3-(arylmethylidene)pyrrolidine-2,5-diones, 12a and 12b, were synthesized and characterized by powder X-ray diffraction utilizing a high-resolution synchrotron X-ray powder technique as well as DFT calculations.

Synthesis, characterization and carbonic anhydrase inhibitory activity of novel benzothiazole derivatives

N-protected amino acids were reacted with substituted benzothiazoles to give the corresponding N-protected amino acid-benzothiazole conjugates (60-89%). Their structures were confirmed by proton nuclear magnetic resonance ((1)H NMR), carbon-13 nuclear magnetic resonance ((13)C NMR), IR and elemental analysis. Their carbonic anhydrase (CA, EC 4.2.1.1) inhibitory activities were determined against two cytosolic human isoforms (hCA I and hCA II), one membrane-associated (hCA IV) and one transmembrane (hCA XII) enzyme by a stopped-flow CO2 hydrase assay method. The new compounds showed rather weak, micromolar inhibitory activity against most of these enzymes.