Methoxy-Substituted Tyramine Derivatives Synthesis, Computational Studies and Tyrosinase Inhibitory Kinetics

Optimization of a Novel Tyrosinase Inhibitory Peptide from Atrina pectinata Mantle and Its Molecular Inhibitory Mechanism

In order to realize the multi-level utilization of marine shellfish resources and to develop the potential biological activity of processing by-products of Atrina pectinata, gelatin was extracted from the mantle and the potential whitening effect of its enzymatic peptides was explored. Taking tyrosinase inhibitory activity as the evaluation index, the enzyme hydrolysate process was optimized by response-surface methodology, and the optimal enzyme hydrolysate conditions were as follows: pH 5.82, 238 min enzyme hydrolysate time, and temperature of 54.5 °C. Under these conditions, the tyrosinase inhibition activity of Atrina pectinata mantle gelatin peptide (APGP) was 88.6% (IC50 of 3.268 ± 0.048 mg/mL). The peptides obtained from the identification were separated by ultrafiltration and LC-MS/MS, and then four new peptides were screened by molecular docking, among which the peptide Tyr-Tyr-Pro (YYP) had the strongest inhibitory effect on tyrosinase with an IC50 value of 1.764 ± 0.025 mM. The molecular-docking results indicated that hydrogen bonding is the main driving force for the interaction of the peptide YYP with tyrosinase. From the Lineweaver-Burk analysis, it could be concluded that YYP is inhibitory to tyrosinase and exhibits a mixed mechanism of inhibition. These results suggest that YYP could be widely used as a tyrosinase inhibitor in whitening foods and pharmaceuticals.

Synthesis and biological evaluation of substituted aurone derivatives as potential tyrosinase inhibitors: in vitro, kinetic, QSAR, docking and drug-likeness studies

Tyrosinase enzyme plays an essential role in melanin biosynthesis and enzymatic browning of fruits and vegetables. To discover potent tyrosinase inhibitors, the present studies were undertaken. In this context, synthetic aurone derivatives 26-50 were designed, synthesized, and structurally elucidated by various spectroscopic techniques including IR, UV, 1H- & 13C-NMR and mass spectrometry. The target compounds 26-50 were screened for their anti-tyrosinase inhibitory potential, and thus kinetic mechanism was analyzed by Lineweaver-Burk plots. All target compounds exhibited good to excellent IC50 values in the range of 7.12 ± 0.32 μM to 66.82 ± 2.44 μM. These synthesized aurone derivatives were found as potent tyrosinase inhibitors relative to the standard kojic acid (IC50 = 16.69 ± 2.81 μM) and the compound 39 inhibited tyrosinase non-competitively (Ki = 11.8 μM) by forming an enzyme-inhibitor complex. The binding modes of these molecules were ascribed through molecular docking studies against tyrosinase protein (PDB ID: 2Y9X). The quantitative structure-activity relationship studies displayed a good correlation between 26-50 structures and their anti-tyrosinase activity (IC50) with a correlation coefficient (R2) of 0.9926. The computational studies were coherent with experimental results and these ligands exhibited good binding values against tyrosinase and interacted with core residues of target protein. Moreover, the drug-likeness analysis also showed that some compounds have a linear correlation with Lipinski's rule of five, indicating good drug-likeness and bioactivity scores for pharmacological targets.Communicated by Ramaswamy H. Sarma.

Evaluation of 2,3-Dihydro-1,5-benzothiazepine Derivatives as Potential Tyrosinase Inhibitors: In Vitro and In Silico Studies

Benzothiazepines are pharmacologically active compounds, frequently utilized as a precursor for acquiring versatile molecules with several bioactivities including anti-inflammatory, anti-human immunodeficiency virus (anti-HIV), analgesic, antitumor, antimicrobial, and antitubercular. In this study, the 2,4-diphenyl-2,3-dihydro-1,5-benzothiazepine scaffold was selected for their in vitro, docking, and druglikeness studies to evaluate their inhibitory potential against mushroom tyrosinase. All synthesized analogues, 1-14, exhibited moderate to good IC₅₀ values ranging from 1.21 to 70.65 μM. The synthesized benzothiazepine derivatives were potent tyrosinase inhibitors, which outperformed the reference kojic acid (IC₅₀ = 16.69 μM). The kinetic analysis revealed that compound 2 (2-(3,4-dimethoxyphenyl)-4-(p-tolyl)-2,3-dihydrobenzo[b][1,4]thiazepine) was a mixed-type tyrosinase inhibitor with a K_i value of 1.01 μM. Molecular modeling studies against tyrosinase protein (PDB ID: 2Y9X) were conducted to recognize the binding modes of these analogues. The utilization of molecular dynamic (MD) simulations enabled the assessment of the protein-ligand complex's dynamic behavior, stability, and binding affinity for the compounds. These simulations ultimately led to the identification of compound 2 as a potential inhibitor of tyrosinase. Additionally, a druglikeness study was conducted, which supported the promising potential of the new analogues as novel antityrosinase agents. The in silico studies were consistent with the in vitro results, showing that these ligands had good binding scores against tyrosinase and interacted with the core residues of the target protein. Gaussian 09 was used for the geometry optimization of all complexes.

Synthesis, in vitro cholinesterase inhibition, molecular docking, DFT and ADME studies of novel 1,3,4-oxadiazole 2-thiol derivatives

A sequence of 1,3,4-oxadiazole 2-thiol derivatives bearing various alkyl or aryl moieties was designed, synthesized, and characterized by modern spectroscopic methods to yield 17 compounds ( 6a - 6q ) which were screened for acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) enzymes in search of 'lead' compounds for the treatment of Alzheimer disease (AD). The compounds 6q, 6p, 6k, 6o, and 6l showed inhibitory capability against AChE and BChE, with IC 50 values ranging from 11.730.49 to 27.360.29 µM for AChE and 21.830.39 to 39.430.44 µM for BChE, inhibiting both enzymes within a limited range. The SAR ascertained that the substitution of the aromatic moiety had a profound effect on the AChE and BChE inhibitory potential as compared to the aliphatic substitutions which were supported by the molecular docking studies. In silico ADME studies reinforced the drug-likeness of most of the synthesized molecules. These results were additionally supplemented by the molecular orbital analysis (HOMO-LUMO) and electrostatic potential maps got from DFT calculations. ESP maps expose that on all structures, there are two potential binding sites conquered by the most positive and most negative districts.

Design, Synthesis, and Structural Characterization of Thioflavones and Thioflavonols as Potential Tyrosinase Inhibitors: In Vitro and In Silico Studies

To find new potential tyrosinase inhibitors, a diverse range of 2-arylchromone-4-thione derivatives (2a-2p) were designed and synthesized by employing a multistep strategy, and the newly synthesized compounds, for the first time, were screened in vitro for their tyrosinase inhibitory activity. In this context, the newly synthesized compounds (2a-2p) were characterized using a combination of several spectroscopic techniques including Fourier transform infrared, UV-vis, ¹H NMR, and ¹³C NMR spectroscopies and electron ionization-mass spectrometry. All the target compounds were potent against tyrosinase as compared to the standard inhibitor kojic acid (half-maximal inhibitory concentration (IC₅₀) = 12.6 ± 0.6 μM). The compounds (2a-2p) produced IC₅₀ values in the range from 1.12 ± 0.04 to 5.68 ± 0.13 μM. Among the synthesized 4-thioflavones and 4-thioflavonols, the compound 2n exhibited excellent tyrosinase inhibitory activity with the lowest IC₅₀ of 1.12 ± 0.04 μM that could be recommended as potential lead candidates to cure tyrosinase-mediated hyperpigmentation in the future. A kinetic study of compound 2n revealed that compound 2n inhibited tyrosinase in a competitive mode. Furthermore, the nontoxic performance of the most beneficial compounds ranging from 1 to 25 g/mL was determined using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide test method for A375 human melanoma cells for the highly efficient target compounds (2m, 2n, 2o, and 2p). Moreover, a molecular modeling study was performed against tyrosinase enzyme (2Y9X) to check the binding interactions of the synthesized compounds (2a-2p) against the target protein. Furthermore, quantitative structure-activity relationship studies were conducted based on an antityrosinase assay. The value of the correlation coefficient (R ²) 0.9997 shows that there was a good correlation between (2a-2p) structures and selected properties. The geometry optimization of all complexes was performed by using Gaussian 09. Additionally, a drug-likeness research was used to establish the potent analogues' positive action as a new antityrosinase agent (2n, 2o, and 2p).

Molecular Docking, Synthesis, and Tyrosinase Inhibition Activity of Acetophenone Amide: Potential Inhibitor of Melanogenesis

Tyrosinase and its related proteins are responsible for pigmentation disorders, and inhibiting tyrosinase is an established strategy to treat hyperpigmentation. The carbonyl scaffolds can be effective inhibitors of tyrosinase activity, and the fact that both benzoic and cinnamic acids are safe natural substances with such a scaffolded structure, it was speculated that hydroxyl-substituted benzoic and cinnamic acid derivatives may exhibit potent tyrosinase inhibitory activity. These moieties were incorporated into new chemotypes that displayed in vitro inhibitory effect against mushroom tyrosinase with a view to explore antimelanogenic ingredients. The most active compound, 2-((3-acetylphenyl)amino)-2-oxoethyl(E)-3-(2,4-dihydroxyphenyl)acrylate (5c), inhibited mushroom tyrosinase with an IC50 of $0.0020\pm 0.0002\mu \text{M}$ , while 2-((3-acetylphenyl)amino)-2-oxoethyl 2,4-dihydroxybenzoate (3c) had an IC50 of $27.35\pm 3.6\mu \text{M}$ in comparison to the positive control arbutin and kojic acid with a tyrosinase inhibitory activity of IC50 of $191.17\pm 5.5\mu \text{M}$ and IC50 of $16.69\pm 2.8\mu \text{M}$ , respectively. Analysis of enzyme kinetics revealed that 5c is a competitive and reversible inhibitor with dissociation constant (Ki) value 0.0072 μM. In silico docking studies with mushroom tyrosinase (PDB ID 2Y9X) predicted possible binding modes in the enzymatic pocket for these compounds. The orthohydroxyl of the cinnamic acid moiety of 5c is predicted to form hydrogen bond with the active site side chain carbonyl of Asn 260 (2.16 Å) closer to the catalytic site Cu ions. The acetyl carbonyl is picking up another hydrogen bond with Asn 81 (1.90 Å). The inhibitor 5c passed the panassay interference (PAINS) alerts. This study presents the potential of hydroxyl-substituted benzoic and cinnamic acids and could be beneficial for various cosmetic formulations.