Sodium Trifluoroacetate mediated Copper-Catalyzed aza-Michael addition of α,ß-unsaturated olefins with aromatic amines.

We present a sodium trifluoroacetate (CF3CO2Na) mediated copper-catalyzed aza-Michael addition of aromatic amines with activated olefins under mild, aqueous reaction conditions. This simplistic protocol employs a copper catalyst (10 mol%) and water as solvent. This transformation occurs precisely with aromatic substituted amines containing both electron-donating (EDG) and electron-withdrawing (EWG) groups. A broad range of substrates were tested under the optimized conditions, which are producing good to moderate yields.

Design, synthesis, spectroscopic characterization, in vitro tyrosinase inhibition, antioxidant evaluation, in silico and kinetic studies of substituted indole-carbohydrazides.

In the current study, twenty-five indole-carbohydrazide derivatives linked to different aryl substitutions were rationally designed and synthesized. The structures of all derivatives were confirmed using different spectroscopic techniques including 1H NMR, 13C NMR, Mass spectrometry, and elemental analysis. The tyrosinase inhibitory activities of all synthetic compounds exhibited IC50 values in the range of 0.070 to > 100 µM. Structure-activity relationships showed that compounds 4f (R = 4-OH, IC50 = 0.070 µM), 8f (R = 4-OH, IC50 = 0.072 µM), and 19e (IC50 = 0.19 µM) with para-OH substituent at the R position was found to be the most active members of all three tested series. Kinetic studies exhibited that compounds 4f, 8f, and 19e are mixed-type inhibitors. Furthermore, toxicity and cell-based anti-melanogenesis assessments were performed on the most potent derivatives and it was shown that 4f, 8f, and 19e had no toxicity at 8 µM and reduced the percent of melanin content to 68.43, 72.61, 73.47 at 8 µM, respectively. In silico analyses of absorption, distribution, metabolism, and excretion (ADME) profile of synthesized compounds showed that these molecules followed drug-likeness rules and acceptable predictive ADMET features. Results of the docking study were almost in line with biological results with ChemPLP values of 53.56 to 79.33. Also, the docking study showed the critical interactions of potent inhibitors with the active site of the enzyme which affects the potency of the synthesized hybrids. Based on molecular dynamic simulations, compound 4f exhibited pronounced interaction with the critical residues of the tyrosinase active site so that the indole ring participated in H-bond interaction with Gly281 and 4-hydroxy benzylidene recorded another H-bond interaction with Asp289 plus hydrophobic interactions with Phe292. Hydrazide linker also exhibited three H-bond interactions with His263 and Gly281.

Rational Design, Synthesis, in Vitro, and in Silico Studies of Chlorophenylquinazolin-4(3H)-One Containing Different Aryl Acetohydrazides as Tyrosinase Inhibitors.

Tyrosinase plays a pivotal role in the hyperpigmentation and enzymatic browning of fruit and vegetable. Therefore, tyrosinase inhibitors can be of interest in industries as depigmentation compounds as well as anti-browning agents. In the present study, a series of chlorophenylquinazolin-4(3H)-one derivative were rationally designed and synthesized. The formation of target compounds was confirmed by spectral characterization techniques such as IR, 1 H-NMR, 13 C-NMR, and elemental analysis. Among the synthesized derivatives, compound 8l was proved to be the most potent inhibitor with an IC50 value of 25.48±1.19 µM. Furthermore, the results of the molecular docking study showed that this compound fitted well in the active site of tyrosinase with the binding score of -10.72.

Evaluating the effects of disubstituted 3-hydroxy-1H-pyrrol-2(5H)-one analog as novel tyrosinase inhibitors.

In the present study, a series of 3-hydroxy-1H-pyrrol-2(5H)-one derivative were rationally designed and synthesized. The structure of targeted compounds was confirmed by IR, 1H NMR, 13C NMR, and elemental analysis. Next, all derivatives were evaluated as tyrosinase inhibitors, and among the synthesized derivatives, compound 6a was proved to be the most potent inhibitor with an IC50 value of 6.98 ± 1.05 µM. Kinetic study of compound 6a confirmed the mixed type of inhibitory activity towards tyrosinase. Furthermore, the results of the molecular docking study showed that this compound fitted well in the active site of tyrosinase and exhibited interaction with important residues of the binding site.

Imino-2H-Chromene Based Derivatives as Potential Anti-Alzheimer's Agents: Design, Synthesis, Biological Evaluation and in Silico Study.

A new series of imino-2H-chromene derivatives were rationally designed and synthesized as novel multifunctional agents against Alzheimer's disease. A set of phenylimino-2H-chromenes as well as the newly synthesized iminochromene derivatives were evaluated as BACE1, acetylcholinesterase (AChE), and butyrylcholinesterase (BuChE) inhibitors. The results indicated that among the iminochromene set, 10c bearing fluorobenzyl moiety was the most potent BACE1 inhibitor with an IC50 value 6.31 µM. In vitro anti-cholinergic activities demonstrated that compound 10a bearing benzyl pendant was the best inhibitor of AChE (% inhibition at 30 µM=24.4) and BuChE (IC50 =3.3 µM). Kinetic analysis of compound 10a against BuChE was also performed and showed a mixed-type inhibition pattern. The neuroprotective assessment revealed that compound 11b, a phenylimino-2H-chromene derivative with hydroxyethyl moiety, provided 32.3 % protection at 25 µM against Aß-induced PC12 neuronal cell damage. In addition, docking and simulation studies of the most potent compounds against BACE1 and BuChE confirmed the experimental results.

Design, synthesis, and biological evaluation of symmetrical azine derivatives as novel tyrosinase inhibitors.

A series of symmetrical azine derivatives containing different substituted benzyl moieties were designed, synthesized, and evaluated for their inhibitory activity against tyrosinase. The results showed that compounds 3e, 3f, 3h, 3i, 3j, and 3k possess effective tyrosinase inhibition with IC50 values ranging from 7.30 µM to 62.60 µM. Particularly, compounds 3f displayed around three-fold improvement in the potency (IC50 = 7.30 ± 1.15 µM) compared to that of kojic acid (IC50 = 20.24 ± 2.28 µM) as the positive control. Kinetic study of compound 3f confirmed uncompetitive inhibitory activity towards tyrosinase indicating that it can bind to enzyme-substrate complex. Next, molecular docking analysis was performed to study the interactions and binding mode of the most potent compound 3f in the tyrosinase active site. Besides, the cytotoxicity of 3f, as well as its potency to reduce the melanin content were also measured on invasive melanoma B16F10 cell line. Also, 3f exhibited above 82% cell viability in the A375 cell line at 10 µM. Consequently, compounds 3f could be introduced as a potent tyrosinase inhibitor that might be a promising candidate in the cosmetics, medicine, and food industry.

Anti-melanogenesis and anti-tyrosinase properties of aryl-substituted acetamides of phenoxy methyl triazole conjugated with thiosemicarbazide: Design, synthesis and biological evaluations.

A series of aryl phenoxy methyl triazole conjugated with thiosemicarbazides were designed, synthesized, and evaluated for their tyrosinase inhibitory activities in the presence of l-dopa and l-tyrosine as substrates. All the compounds showed tyrosinase inhibition in the sub-micromolar concentration. Among the derivatives, compound 9j bearing benzyl displayed exceptionally high potency against tyrosinase with IC50 value of 0.11 µM and 0.17 µM in the presence of l-tyrosine and l-dopa as substrates which is significantly lower than that of kojic acid as the positive control with an IC50 value of 9.28 µM for l-tyrosine and 9.30 µM for l-dopa. According to Lineweaver-Burk plot, 9j demonstrated an uncompetitive type of inhibition in the kinetic assay. Also, in vitro antioxidant activities determined by DPPH assay recorded an IC50 value of 68.43 µM for 9i. The melanin content of 9j was determined on B16F10 melanoma human cells which demonstrated a significant reduction of the melanin content. Moreover, the binding energies corresponding to the same ligand as well as computer-aided drug-likeness and pharmacokinetic studies were also carried out. Compound 9j also possessed metal chelation potential correlated to its high anti-TYR activity.

A Series of Benzylidenes Linked to Hydrazine-1-carbothioamide as Tyrosinase Inhibitors: Synthesis, Biological Evaluation and Structure-Activity Relationship.

Tyrosinase is a type 3 copper enzyme responsible for skin pigmentation disorders, skin cancer, and enzymatic browning of vegetables and fruits. In the present article, 12 small molecules of 2-benzylidenehydrazine-1-carbothioamide were designed, synthesized and evaluated for their anti-tyrosinase activities followed by molecular docking and pharmacophore-based screening. Among synthesized thiosemicarbazone derivatives, one compound, (2E)-2-[(4-nitrophenyl)methylidene]hydrazine-1-carbothioamide, is the strongest inhibitor of mushroom tyrosinase with IC50 of 0.05 µM which demonstrated a 128-fold increase in potency compared to the positive control. Kinetic studies also revealed mix type inhibition by this compound. Docking studies confirmed the complete fitting of the synthesized compounds into the tyrosinase active site. The results underline the potential of 2-benzylidenehydrazine-1-carbothioamides as potent pharmacophore to extend the tyrosinase inhibition in drug discovery.

Biotransformation of acetoin to 2,3-butanediol: Assessment of plant and microbial biocatalysts.

2,3-Butanediol (2,3-BD) is a valuable bulk chemical owing to its extensive application in chemical and pharmaceutical industry with diverse applications in drug, cosmetics and food products. In the present study, the biotransformation of acetoin to 2,3-BD by five plant species (Brassica oleracea, Brassica rapa, Daucuscarota, Pastinaca sativa, and Raphnussativus) and five microorganisms (Aspergillusfoetidus, Penicillumcitrinum, Saccharomyces carlbergensis, Pichiafermentans, and Rhodotrulaglutinis) was investigated as a method for the production of 2,3-BD, which can serve as an alternative to the common pentoses and hexoses fermentation by microorganisms. The produced 2,3-BD stereoisomers were characterized and their total conversion yields were determined. The results showed that the examined plants can be used as a green factory for the production of all 2,3-BD stereoisomers, except B. rapa. In microorganisms, P. fermentans and S. carlbergensis produced (-)-2R,3R and mesobutanediol, while P. citrinum produced (+)-2S,3S and mesobutanediol. R. glutinis and A. foetidus produced all three isomers. In conclusion, efficient whole-cell biocatalysts from plants and microorganisms were determined in the bioconversion of acetoin to 2,3-BD. The profile of produced stereoisomers demonstrated that microorganisms produce more specific stereoisomers.