Identification by shape-based virtual screening and evaluation of new tyrosinase inhibitors

Identification of human phosphoglycerate mutase 1 (PGAM1) inhibitors using hybrid virtual screening approaches

PGAM1 plays a critical role in cancer cell metabolism through glycolysis and different biosynthesis pathways to promote cancer. It is generally known as a crucial target for treating pancreatic ductal adenocarcinoma, the deadliest known malignancy worldwide. In recent years different studies have been reported that strived to find inhibitory agents to target PGAM1, however, no validated inhibitor has been reported so far, and only a small number of different inhibitors have been reported with limited potency at the molecular level. Our in silico studies aimed to identify potential new PGAM1 inhibitors that could bind at the allosteric sites. At first, shape and feature-based models were generated and optimized by performing receiver operating characteristic (ROC) based enrichment studies. The best query model was then employed for performing shape, color, and electrostatics complementarity-based virtual screening of the ChemDiv database. The top two hundred and thirteen hits with greater than 1.2 TanimotoCombo score were selected and then subjected to structure-based molecular docking studies. The hits yielded better docking scores than reported compounds, were selected for subsequent structural similarity-based clustering analysis to select the best hits from each cluster. Molecular dynamics simulations and binding free energy calculations were performed to validate their plausible binding modes and their binding affinities with the PGAM1 enzyme. The results showed that these compounds were binding in the reported allosteric site of the enzyme and can serve as a good starting point to design better active selective scaffolds against PGAM1enzyme.

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.

Discovery of Resorcinol-Based Polycyclic Structures as Tyrosinase Inhibitors for Treatment of Parkinson's Disease

Tyrosinase is involved in the synthesis of neuromelanin in the substantia nigra, which is closely correlated with the pathogenesis of Parkinson's disease. Herein, we identified S05014 (l-Tyr, IC₅₀ = 6.25 ± 1.43 nM; l-Dopa, IC₅₀ = 0.64 ± 0.40 μM) as a highly effective tyrosinase inhibitor. It could inhibit the tyrosinase function from different origins and decrease the expression of tyrosinase. S05014 presented good medication safety and inhibited melanogenesis in a dose-dependent manner. Moreover, as a resorcinol derivative, S05014 could scavenge the 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical and significantly reduce the overproduction of LPS-induced reactive oxidative species (ROS), indicating its antioxidative profile. S05014 exhibited an excellent neuroprotective effect against methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) impairment in vitro and could remarkably alleviate movement abnormalities and exploratory activities in vivo. Altogether, S05014 is considered as a promising inhibitor for tyrosinase, melanogenesis, and oxidative stress and has great potential to be utilized in anti-Parkinsonian syndrome. From this point of view, tyrosinase inhibition has been further confirmed to be a novel strategy to improve locomotor capacity and treat Parkinson's disease.

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.

Discovery and Biological Evaluation of a Novel Highly Potent Selective Butyrylcholinsterase Inhibitor

To discover novel BChE inhibitors, a hierarchical virtual screening protocol followed by biochemical evaluation was applied. The most potent compound 8012-9656 (eqBChE IC₅₀ = 0.18 ± 0.03 μM, hBChE IC₅₀ = 0.32 ± 0.07 μM) was purchased and synthesized. It inhibited BChE in a noncompetitive manner and could occupy the binding pocket forming diverse interactions with the target. 8012-9656 was proven to be safe in vivo and in vitro and showed comparable performance in ameliorating the scopolamine-induced cognition impairment to tacrine. Additionally, treatment with 8012-9656 could almost entirely recover the Aβ_1-42 (icv)-impaired cognitive function to the normal level and showed better behavioral performance than donepezil. The evaluation of the Aβ_1-42 total amount confirmed its anti-amyloidogenic profile. Moreover, 8012-9656 possessed blood-brain barrier (BBB) penetrating ability, a long T_1/2, and low intrinsic clearance. Hence, the novel potential BChE inhibitor 8012-9656 can be considered as a promising lead compound for further investigation of anti-AD agents.

A comprehensive review on tyrosinase inhibitors

Tyrosinase is a multi-copper enzyme which is widely distributed in different organisms and plays an important role in the melanogenesis and enzymatic browning. Therefore, its inhibitors can be attractive in cosmetics and medicinal industries as depigmentation agents and also in food and agriculture industries as antibrowning compounds. For this purpose, many natural, semi-synthetic and synthetic inhibitors have been developed by different screening methods to date. This review has focused on the tyrosinase inhibitors discovered from all sources and biochemically characterised in the last four decades.

Natural and Bioinspired Phenolic Compounds as Tyrosinase Inhibitors for the Treatment of Skin Hyperpigmentation: Recent Advances

One of the most common approaches for control of skin pigmentation involves the inhibition of tyrosinase, a copper-containing enzyme which catalyzes the key steps of melanogenesis. This review focuses on the tyrosinase inhibition properties of a series of natural and synthetic, bioinspired phenolic compounds that have appeared in the literature in the last five years. Both mushroom and human tyrosinase inhibitors have been considered. Among the first class, flavonoids, in particular chalcones, occupy a prominent role as natural inhibitors, followed by hydroxystilbenes (mainly resveratrol derivatives). A series of more complex phenolic compounds from a variety of sources, first of all belonging to the Moraceae family, have also been described as potent tyrosinase inhibitors. As to the synthetic compounds, hydroxycinnamic acids and chalcones again appear as the most exploited scaffolds. Several inhibition mechanisms have been reported for the described inhibitors, pointing to copper chelating and/or hydrophobic moieties as key structural requirements to achieve good inhibition properties. Emerging trends in the search for novel skin depigmenting agents, including the development of assays that could distinguish between inhibitors and potentially toxic substrates of the enzyme as well as of formulations aimed at improving the bioavailability and hence the effectiveness of well-known inhibitors, have also been addressed.

MicroRNAs as a Novel Tool in the Diagnosis of Liver Lipid Dysregulation and Fatty Liver Disease

In recent years, metabolic disorder, especially fatty liver disease, has been considered a major challenge to global health. The attention of researchers focused on expanding knowledge of the regulation mechanism behind these diseases and towards the new diagnostics tools and treatments. The pathophysiology of the fatty liver disease is undoubtedly complex. Abnormal hepatic lipid accumulation is a major symptom of most metabolic diseases. Therefore, the identification of novel regulation factors of lipid metabolism is important and meaningful. As a new diagnostic tool, the function of microRNAs during fatty liver disease has recently come into notice in biological research. Accumulating evidence supports the influence of miRNAs in lipid metabolism. In this review, we discuss the potential role of miRNAs in liver lipid metabolism and the pathogenesis of fatty liver disease.