Synthesis of novel compounds containing morpholine and 5(4H)-oxazolone rings as potent tyrosinase inhibitors

Inhibitory Activity of 4-Benzylidene Oxazolones Derivatives of Cinnamic Acid on Human Acetylcholinesterase and Cognitive Improvements in a Mouse Model

We synthesized seven (Z)-benzylidene-2-(E)-styryloxazol-5(4H)-ones derivatives of cinnamic acid and evaluated the ability of these compounds to inhibit human acetylcholinesterase (hAChE). The most potent compound was evaluated for cognitive improvement in short-term memory. The seven compounds reversibly inhibited the hAChE between 51 and 75% at 300 μM, showed an affinity (Ki) from 2 to 198 μM, and an IC50 from 9 to 246 μM. Molecular docking studies revealed that all binding moieties are involved in the non-covalent interactions with hAChE for all compounds. In addition, in silico pharmacokinetic analysis was carried out to predict the compounds' blood-brain barrier (BBB) permeability. The most potent inhibitor of hAChE significantly improved cognitive impairment in a modified Y-maze test (5 μmol/kg) and an Object Recognition Test (10 μmol/kg). Our results can help the rational design of hAChE inhibitors to work as potential candidates for treating cognitive disorders.

Synthesis, Antimicrobial, Anti-virulence and Anticancer Evaluation of New 5(4H)-Oxazolone-Based Sulfonamides

Since the synthesis of prontosil the first prodrug shares their chemical moiety, sulfonamides exhibit diverse modes of actions to serve as antimicrobials, diuretics, antidiabetics, and other clinical applications. This inspiring chemical nucleus has promoted several research groups to investigate the synthesis of new members exploring new clinical applications. In this study, a novel series of 5(4H)-oxazolone-based-sulfonamides (OBS) 9a–k were synthesized, and their antibacterial and antifungal activities were evaluated against a wide range of Gram-positive and -negative bacteria and fungi. Most of the tested compounds exhibited promising antibacterial activity against both Gram-positive and -negative bacteria particularly OBS 9b and 9f. Meanwhile, compound 9h showed the most potent antifungal activity. Moreover, the OBS 9a, 9b, and 9f that inhibited the bacterial growth at the lowest concentrations were subjected to further evaluation for their anti-virulence activities against Pseudomonas aeruginosa and Staphylococcus aureus. Interestingly, the three tested compounds reduced the biofilm formation and diminished the production of virulence factors in both P. aeruginosa and S. aureus. Bacteria use a signaling system, quorum sensing (QS), to regulate their virulence. In this context, in silico study has been conducted to assess the ability of OBS to compete with the QS receptors. The tested OBS showed marked ability to bind and hinder QS receptors, indicating that anti-virulence activities of OBS could be due to blocking QS, the system that controls the bacterial virulence. Furthermore, anticancer activity has been further performed for such derivatives. The OBS compounds showed variable anti-tumor activities, specifically 9a, 9b, 9f and 9k, against different cancer lines. Conclusively, the OBS compounds can serve as antimicrobials, anti-virulence and anti-tumor agents.

Recent advances in the design and discovery of synthetic tyrosinase inhibitors

Tyrosinase is a copper-containing metalloenzyme that is responsible for the rate-limiting catalytic step in the melanin biosynthesis and enzymatic browning. As a promising target, tyrosinase inhibitors can be used as skin whitening agents and food preservatives, thus having broad potential in the fields of food, cosmetics, agriculture and medicine. From 2015 to 2020, numerous synthetic inhibitors of tyrosinase have been developed to overcome the challenges of low efficacy and side effects. This review summarizes the enzyme structure and biological functions of tyrosinase and demonstrates the recent advances of synthetic tyrosinase inhibitors from the perspective of medicinal chemistry, providing a better understanding of the catalytic mechanisms and more effective tyrosinase inhibitors.

SAR and QSAR research on tyrosinase inhibitors using machine learning methods

Tyrosinase is a key rate-limiting enzyme in the process of melanin synthesis, which is closely related to human pigmentation disorders. Tyrosinase inhibitors can down-regulate tyrosinase to effectively reduce melanin synthesis. In this work, we conducted structure-activity relationship (SAR) study on 1097 diverse mushroom tyrosinase inhibitors. We applied five kinds of machine learning methods to develop 15 classification models. Model 5B built by fully connected neural networks and ECFP4 fingerprints achieved the highest prediction accuracy of 91.36% and Matthews correlation coefficient (MCC) of 0.81 on the test set. The applicability domains (AD) of classification models were defined by d S T D - P R O method. Moreover, we clustered the 1097 inhibitors into eight subsets by K-Means to figure out inhibitors' structural features. In addition, 10 quantitative structure-activity relationship (QSAR) models were constructed by four machine learning methods based on 813 inhibitors. Model 6 J, the best QSAR model, was developed by fully connected neural networks with 50 RDKit descriptors. It resulted in a coefficient of determination (r ²) of 0.770 and a root mean squared error (RMSE) of 0.482 on the test set. The AD of Model 6 J was visualized by Williams plot. The models built in this study can be obtained from the authors.

A systematic review of synthetic tyrosinase inhibitors and their structure-activity relationship

Tyrosinase is a copper-containing oxidation enzyme, which is responsible for the production of melanin. This enzyme is widely distributed in microorganisms, animals and plants, and plays an essential role in undesirable browning of fruits and vegetables, antibiotic resistance, skin pigment formation, sclerotization of cuticle, neurodegeneration, etc. Hence, it has been recognized as a therapeutic target for the development of antibrowning agents, antibacterial agents, skin-whitening agents, insecticides, and other therapeutic agents. With great potential application in food, agricultural, cosmetic and pharmaceutical industries, a large number of synthetic tyrosinase inhibitors have been widely reported in recent years. In this review, we systematically summarized the advances of synthetic tyrosinase inhibitors in the literatures, including their inhibitory activity, cytotoxicity, structure-activity relationship (SAR), inhibition kinetics, and interaction mechanisms with the enzyme. The collected information is expected to provide a rational guidance and effective strategy to develop novel, potent and safe tyrosinase inhibitors for better practical applications in the future.

Synthesis, Anti-Bacterial and Anti-Oxidant Activity of Azo-Oxazolone and Their Ring Opening Azo-Benzamide Derivatives

This article describes the controlled synthesis and characterization of azo oxazolone scaffold compounds containing multifunctional groups such as carbonyl group, imine and carbon-carbon double bond. The reaction of the azo-oxazolone with aromatic amines led to the ring-opening of the azo-oxazolone into the corresponding azo-benzamide derivatives in a short time (average 10 min), resulting in high yield (>90%). All newly synthesized compounds were characterized by the common spectral analysis such as UV, IR, ¹H-NMR, ¹³CNMR, Elemental analysis and MS spectrometry.

OBJECTIVE

The aim of the study was to synthesize new bioactive azo-benzamides by using azo-oxazolone as a synthon utilizing its ring-opening function.

MATERIALS AND METHODS

Azo-benzamide derivatives were prepared in very good yield via ring-opening reaction of azo-oxazolone with aromatic amines in the presence of acetic acid under reflux for few minutes.

RESULTS AND DISCUSSION

Chemical structures of the newly synthesized compounds were characterized by UV, IR, ¹H-NMR, ¹³C-NMR, Elemental analysis and MS spectrometry.

CONCLUSION

The new azo-oxazolone 4 and azo-benzamide compounds 5a, 5c, 5f, 5h, 5j were screened against Escherichia coli as G(-ve) and Staphylococcus aureus as G(+ve) using ciprofloxacin as a standard. All compounds showed high inhibition potency against E-Coli but low inhibition for S-aureus. Compounds 4, 5c, and 5J showed more reactivity against E-coli. Others: Also, the compounds were tested for their anti-oxidant activity by both DPPH and FRAP methods. The results showed that some compounds possessed moderate anti-oxidant activity in comparison to ascorbic acid as control, typically the compounds bearing OCH₃ and OCH₂CH₃ groups.

Synthesis, computational molecular docking analysis and effectiveness on tyrosinase inhibition of kojic acid derivatives

Tyrosinase inhibitors have become increasingly important as whitening agents and for the treatment of pigmentary disorders. In this study, the synthesis of kojic acid derivatives having 2-substituted-3-hydroxy-6-hyroxymethyl/chloromethyl/methyl/morpholinomethylpiperidinyl- methyl/pyrrolidinylmethyl-4H-pyran-4-one structure (compounds 1-30) with inhibitory effects on tyrosinase enzyme were described. One-pot Mannich reaction was carried out by using kojic acid/chlorokojic acid/allomaltol and substituted benzylpiperazine derivatives in presence of formaline. Subsequently, cyclic amine (morpholine, piperidine and pyrrolidine) derivatives of the 6th-position of chlorokojic acid were obtained with nucleophilic substitutions in basic medium. The structures of new compounds were identified by FT-IR, ¹H- and ¹³C NMR, ESI-MS and elemental analysis data. The potential mushroom tyrosinase inhibitory activity of the compounds were evaluated by the spectrophotometric method using l-DOPA as a substrate and kojic acid as the control agent. The potential inhibitory activity was also investigated in silico using molecular docking simulation method. Tyrosinase inhibitory action was significantly more efficacious for several compounds (IC₅₀: 86.2-362.1 µM) than kojic acid (IC₅₀: 418.2). Compound 3 bearing 3,4-dichlorobenzyl piperazine moiety was proven to have the highest inhibitory activity. The results of docking studies showed that according to the predicted conformation of compound 3 in the enzyme binding site, hydroxymethyl group provides a metal complex with copper ions and enzyme. Thus, this interaction explain the high inhibitory activities of the compounds 1, 3 and 4 possessing hydroxymethyl substituent supporting the mushroom assay results with docking studies. In accordance with the results, it is suggested that Mannich bases of kojic acid bearing substituted benzyl piperazine groups (compounds 1, 3, 4, 11, 13, 14, 23, 24, 28, and 29) could be promising antityrosinase agents. Additionally, considering the relationship between tyrosinase inhibitory activity results and molecular docking, a new tyrosinase inhibition mechanism can be proposed.

Synthesis, characterization, antioxidant power and acute toxicity of some new azo-benzamide and azo-imidazolone derivatives with in vivo and in vitro antimicrobial evaluation

In this research paper, a stepwise chemical reaction was conducted to synthesize and develop of a new potent azo-oxazolone, which was used as prototypical molecule for production of two series of azo-benzimide (5a-j) and azo-imidazolone (6a-j). FT-IR, ¹H NMR, ¹³C NMR and CHN analysis were used for the structural elucidation. The high biological efficiency of newly obtained compounds was confirmed by in vitro antioxidant efficacy and in vitro antimicrobial activity against gram-positive and gram-negative bacteria via disc diffusion and tube dilution techniques. In addition, in vivo anti-microbial activity of some of the synthesized compounds was determined by using burnt rats which infected by Staphylococcus aureus. Tested compounds have shown high anti-microbial activity and wound healing in comparison to ucederm as a control. In vivo acute toxicity was carried out by up and down method for the compounds 4, 5d and 6d. The limited test dose was 2000 mg/kg, while the maximum tolerated dose was 5000 mg/kg which has administered no lethality recorded.

Synthesis, Spectroscopic Characterization and Polymerization Abilities of Blue and Green Light Emitting Oxazol-5-one Fluorophores

New fluorescent thiophenyl group containing oxazol-5-one fluorophores of 3a (4-(3-thiophenylmethylene)-2-phenyloxazol-5-one), 3b (4-(3-thiophenylmethylene)-2-(4-tolyl)oxazol-5-one) and 3c (4-(3-thiophenylmethylene)-2-(4-nitrophenyl)oxazol-5-one) were synthesized and characterized. The newly synthesized oxazol-5-ones absorption and fluorescence characteristics were studied in some solvents of varying polarities. The heterocyclic chromophores were fluorescent, with two of them, 3a and 3b, emitting blue light, whilst the other one, 3c, emitting green light. The emission maxima of the derivatives varied between 415 and 572 nm according as the extent of conjugation and solvent polarity. As solvent polarity increased, 3c derivatives emission spectra displayed a large bathochromic shift, which revealed the considerable change of the dipole moment of the fluorescent structure because of an intramolecular charge transfer interaction. Furthermore, oxazolones polymerization ability via the thiophenyl group linked to the oxazol-5-one heterocycle showed that copolymerization of 3a was achieved, but homopolymerization was not observed.

Breaking aziridines to construct morpholines with a gold(i)-catalyzed tandem ring-opening and cycloisomerization reaction

A convenient synthetic method for the construction of morpholine derivatives from easily available aziridines and propargyl alcohols has been successfully developed. A tandem nucleophilic ring-opening of aziridine/6-exo-dig cyclization/double bond isomerization sequence was achieved by using a single gold(i) catalyst under mild conditions. The gold(i) catalyst served as a π acid and also a σ acid to realize the dual activation of both reactants in this reaction. The obtained unsaturated morpholine products could be easily hydrogenated to achieve target morpholine derivatives with good diastereoselectivities in high yields.

The water soluble peripherally tetra-substituted zinc(ii), manganese(iii) and copper(ii) phthalocyanines as new potential anticancer agents

In this study, [2-(2-morpholin-4-ylethoxy)ethoxy] group substituted zinc(ii), manganese(iii) and copper(ii) phthalocyanines 2–4 and their water soluble derivatives 2a, 3a and 4a were synthesized and the interactions of compounds 2a, 3a and 4a with CT-DNA and supercoiled pBR322 plasmid DNA were investigated.