Design, synthesis, and molecular docking of cysteine-based sulphonamide derivatives as antimicrobial agents

Background and purpose:

The preponderance of microbial infections remains a global challenge. In the present study, synthesis of novel cysteine-based antimicrobial agents and their biological evaluation is reported.

Experimental approach:

The reaction of p-toluenesulphonyl chloride with cysteine afforded 2-{[(4-methylphenyl)sulphonyl]amino}-3-sulphanylpropanoic acid (3) which was acetylated based on Lumiere-Barbier method using acetic anhydride. The ammonolysis of the acetylated compound (4) gave the carboxamide derivative (5) which reacted with aniline, aminopyridine and diaminopyrimidine via nickel catalyzed Buchwald-Hartwig amidation reaction to afford compounds 6a, 6b, and 6c, respectively. The compounds were characterized using FTIR, ¹H-NMR, ¹³C-NMR, and elemental analysis. The in vitro antimicrobial activities were determined. Their physicochemical properties were generated in silico and the molecular docking studied bacterial and fungal infections.

Findings/Results:

Compounds 4, 6b, and 6c exhibited excellent in vitro antibacterial activities while compound 4 had the best antifungal activities. From the in silico antimicrobial results, compound 3 had a better binding affinity (-10.95 kcal/mol) than penicillin (-10.89 kcal/mol) while compounds 3 and 4 had binding affinities (-10.07 and -10.62kcal/mol) comparable to ketoconazole (-10.85 kcal/mol).

Conclusion and implication:

All the synthesized compounds exhibited significant antibacterial and antifungal activities and were confirmed to be potential antimicrobial agents.

New sulphonamide pyrolidine carboxamide derivatives: Synthesis, molecular docking, antiplasmodial and antioxidant activities

Carboxamides bearing sulphonamide functionality have been shown to exhibit significant lethal effect on Plasmodium falciparum, the causative agent of human malaria. Here we report the synthesis of thirty-two new drug-like sulphonamide pyrolidine carboxamide derivatives and their antiplasmodial and antioxidant capabilities. In addition, molecular docking was used to check their binding affinities for homology modelled P. falciparum N-myristoyltransferase, a confirmed drug target in the pathogen. Results revealed that sixteen new derivatives killed the parasite at single-digit micromolar concentration (IC₅₀ = 2.40–8.30 μM) and compounds 10b, 10c, 10d, 10j and 10o scavenged DPPH radicals at IC₅₀s (6.48, 8.49, 3.02, 6.44 and 4.32 μg/mL respectively) comparable with 1.06 μg/mL for ascorbic acid. Compound 10o emerged as the most active of the derivatives to bind to the PfNMT with theoretical inhibition constant (K_i = 0.09 μM) comparable to the reference ligand pyrazole-sulphonamide (K_i = 0.01 μM). This study identifies compound 10o, and this series in general, as potential antimalarial candidate with antioxidant activity which requires further attention to optimise activity.

Novel Leu-Val Based Dipeptide as Antimicrobial and Antimalarial Agents: Synthesis and Molecular Docking

The increase of antimicrobial resistance (AMR) and antimalarial resistance are complex and severe health issues today, as many microbial strains have become resistant to market drugs. The choice for the synthesis of new dipeptide-carboxamide derivatives is as a result of their wide biological properties such as antimicrobial, anti-inflammatory, and antioxidant activities. The condensation reaction of substituted benzenesulphonamoyl pentanamides with the carboxamide derivatives using peptide coupling reagents gave targeted products (8a-j). The in silico antimalarial and antibacterial studies showed good interactions of the compounds with target protein residues and a higher dock score in comparison with standard drugs. In the in vivo study, compound 8j was the most potent antimalarial agent with 61.90% inhibition comparable with 67% inhibition for Artemisinin. In the in vitro antimicrobial activity, compounds 8a and 8b (MIC 1.2 × 10⁻³ M and 1.1 × 10⁻³ M) were most potent against S. aureus; compound 8a, 8b, and 8j with MIC 6.0 × 10⁻³ M, 5.7 × 10⁻⁴ M, and 6.5 × 10⁻⁴ M, respectively, were the most active against B. subtilis; compound 8b (MIC 9.5 × 10⁻⁴ M) was most active against E.coli while 8a, 8b and 8d were the most active against S. typhi. Compounds 8c and 8h (MIC 1.3 × 10⁻³ M) each were the most active against C. albicans, while compound 8b (MIC 1.3 × 10⁻⁴ M) was most active against A. niger.

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 and biological evaluation of Val-Val dipeptide-sulfonamide conjugates

Novel Val-Val dipeptide-benzenesulfonamide conjugates were reported in this study. These were achieved by a condensation reaction of p-substituted benzenesulfonamoyl alkanamides with 2-amino-4-methyl-N-substituted phenyl butanamide using classical peptide-coupling reagents. The compounds were characterized using Fourier transform infrared, ¹ H-nuclear magnetic resonance (NMR), ¹³ C-NMR, and electrospray ionization-high-resolution mass spectrometry spectroscopic techniques. As predicted from in silico studies, the Val-Val dipeptide-benzenesulfonamide conjugates exhibited antimalarial and antioxidant properties that were analogous to the standard drug. The synthesized compounds were evaluated for in vivo antimalarial activity against Plasmodium berghei. The hematological analysis was also conducted on the synthesized compounds. At 50 mg/kg body weight, compounds 8a, 8d, and 8g-i inhibited the multiplication of the parasite by 48-54% on Day 7 of posttreatment exposure, compared with the 67% reduction with artemisinin. All the synthesized dipeptides had a good antioxidant property, but it was less when compared with vitamin C. The dipeptides reported herein showed the ability to reduce oxidative stress arising from the malaria parasite.

Synthesis of proline derived benzenesulfonamides: A potent anti-Trypanosoma brucei gambiense agent

Thousands of death in Africa and other developing nations are still attributed to trypanosomiasis. Excessive sleep has been associated with increased inflammation. We report herein, the synthesis, antitrypanosomal and anti-inflammatory activities of eight new carboxamide derivatives bearing substituted benzenesulfonamides. The base promoted reactions of l-proline and L-4-hydroxyproline with substituted benzenesulfonyl chlorides gave the benzenesulfonamides (11a-h) in excellent yields. Boric acid mediated amidation of the benzenesulfonamides (11a-h) and p-aminobenzoic acid (12) gave the new carboxamides (13a-h) in excellent yields. The new carboxamides were tested for their antitrypanosomal and anti-inflammatory activities against Trypanosome brucei gambiense and inhibition of carrageenan-induced rat paw edema. Compound 13f was the most potent antitrypanosomal agent with an IC50 value of 2 nM as against 5 nM for melarsoprol; whereas compound 13a was the most potent anti-inflammatory agent with percentage inhibition of carrageenan-induced rat paw edema of 58, 60, 67 and 84% after 0.5 h, 1 h, 2 h and 3 h administration respectively. The structure-activity relationship study revealed that substitution at the para position in the benzenesulfonamide ring increased both the antitrypanosomal and anti-inflammatory activities. The 4-hydroxyprolines (13a-d) showed higher anti-inflammatory activity than the prolines (13e-h). In contrast, the prolines (13e-h) had higher antitrypanosomal activities than the 4-hydroxyprolines. The link between excessive sleep and inflammation makes the report of this class of compounds possessing both antitrypanosomal and anti-inflammatory activity worthwhile. The pharmacokinetic studies showed that the compounds would not pose oral bioavailability, transport and permeability problems.

Novel Phenoxazinones as potent agonist of PPAR-α: design, synthesis, molecular docking and in vivo studies

Background

The use of statin, a 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor for the treatment of dyslipidemia has been associated with dose limiting hepatoxicity, mytotoxicity and tolerability due to myalgias thereby necessitating the synthesis of new drug candidates for the treatment of lipid disorder.

Methods

The reaction of appropriate benzenesulphonamide with substituted phenoxazinone in the presence of phenylboronic acid gave the targeted compounds. The molecular docking study were carried out using autodock tool against peroxisome proliferator activated receptor alpha. The in vivo lipid profile were assayed using conventional methods. The kidney and liver function test were carried out to assess the effect of the derivatives on the organs. The LD₅₀ of the most active derivatives were determined using mice.

Results

The targeted compounds were successfully synthesized in excellent yields and characterized using spectroscopic techniques. The results of the molecular docking experiment showed that they were good stimulant of peroxisome proliferator activated receptor alpha. Compound 9f showed activity at Ki of 2.8 nM and binding energy of 12.6 kcal/mol. All the compounds tested reduced triglyceride, total cholesterol, low density lipoprotein cholesterol and very low density lipoprotein cholesterol level in the mice model. Some of the reported compounds also increased high density lipoprotein cholesterol level in the mice. The compounds did not have appreciable effect on the kidney and liver of the mice used. The LD₅₀ showed that the novel compounds have improved toxicity profile.

Conclusion

The synthesis of fifteen new derivatives of carboxamides bearing phenoxazinone and sulphonamide were successful. The compounds possessed comparable activity to gemfibrozil. The reported compounds had better toxicity profile than gemfibrozil and could serve as a replacement for the statins and fibrate class of lipid agents.

Angular Phenozaxine Ethers as Potent Multi-microbial Targets Inhibitors: Design, Synthesis, and Molecular Docking Studies

The reaction of diaza-5H-benzo[a]phenoxazin-5-one and 5H-benzo[a]phenoxazin-5-one with various phenols catalyzed by Pd/t-BuXPhos/K3PO4 system gave previously unknown ether derivatives (7a-f and 8a-f) in good yields. UV-visible, FTIR, and 1H NMR data were used to confirm structures of the synthesized compounds. The parent compounds and the derivatives were screened in-silico for their drug-likeness and binding affinities to the microbial targets through molecular docking. Molinspiration software and AutoDock were used for the drug-likeness and docking studies, respectively. All the synthesized compounds showed strong drug-likeness. They also showed excellent binding affinities with glucosamine-6-phosphate synthase (2VF5), AmpC beta-lactamase (1KE4), and Lanosterol-14α-demethylase (3JUV), with compound 7e having the highest binding energies -9.5, -9.3, and -9.3 kcal/mol, respectively. These were found to be higher than the binding energies of the standard drugs. The binding energies of ciprofloxacin with 2VF5 and 1KE4 were -7.8 and -7.5 kcal/mol, respectively, while that of ketoconazole with 3JUV was -8.6 kcal/mol. The study showed that the synthesized compounds have multi-target inhibitory effects and can be very useful in multi-drug resistance cases. A 2D quantitative structural activity relationship (QSAR) model against target Glucosamine-6-phosphate synthase (2VF5) was developed using partial least squares regression (PLS) with good internal prediction (R2 = 0.7400) and external prediction (R2_ predicted = 0.5475) via Molecular Operating Environment (2014).