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A well‐known key enzyme in melanogenesis and hyperpigmentation is tyrosinase. The present study introduces a novel series of thiophenyl‐pyrazolylthiazole‐coumarin hybrids (6a–6h) as tyrosinase inhibitors. The in‐vitro tyrosinase inhibition results indicated that all compounds have strong tyrosinase inhibitory activity, particularly compound 6g (IC50 = 0.043 ± 0.006 μM), was identified as the most active compound compared to the positive control (kojic acid, IC50 = 18.521 ± 1.162 μM). Lineweaver‐Burk plots were employed to analyze the kinetic mechanism, and compound 6g formed an enzyme‐inhibitor complex by inhibiting tyrosinase non‐competitively. Furthermore, all compounds demonstrated excellent antioxidant activity against DPPH. MTT assay was used to screen the cytotoxicity of all compounds on B16F10 melanoma cells, and they had no toxic effect on the cells. The binding affinity of compounds with tyrosinase was also investigated using molecular docking, and the ligands displayed good binding energy values. These molecules could be a promising lead for skin pigmentation and associated diseases as nontoxic pharmacological scaffolds. [ABSTRACT FROM AUTHOR]

To develop new alkaline phosphatase inhibitors (ALP), a series of pyrazolo-oxothiazolidine derivatives were synthesized and biologically assessed, and the results showed that all of the synthesized compounds significantly inhibited ALP. Specifically, compound 7g displayed the strongest inhibitory activity (IC50 = 0.045 ± 0.004 μM), which is 116-fold more active than monopotassium phosphate (IC50 = 5.242 ± 0.472 μM) as a standard reference. The most potent compound among the series (7g) was checked for its mode of binding with the enzyme and shown as non-competitively binding with the target enzyme. The antioxidant activity of these compounds was examined to investigate the radical scavenging effect. Moreover, the MTT assay method was performed to evaluate their toxic effects on the viability of MG-63 human osteosarcoma cells, and all compounds have no toxic effect on the cells at 4 μM. Computational research was also conducted to examine the binding affinity of the ligands with alkaline phosphatase, and the results revealed that all compounds showed good binding energy values within the active site of the target. Therefore, these novel pyrazolo-oxothiazolidine derivatives might be employed as promising pharmacophores for potent and selective alkaline phosphatase inhibitors. [ABSTRACT FROM AUTHOR]

[Display omitted] • A series of 1,3,4-thiadiazol-1,3,4-oxadiazol-acetamide derivatives (7a – 7j) were synthesized as elastase inhibitors. • The in-vitro elastase inhibitory activity of all synthesized compounds was determined successfully. • The kinetic mechanism was investigated by Lineweaver-Burk plots. • MTT assay was used to evaluate the cytotoxicity of all compounds on B16F10 melanoma cell lines. • Molecular docking was applied to investigate the binding affinity of compounds with elastase and the ligands showed good binding energy values. Considering the biological significance of 1,3,4-thiadiazole/oxadiazole heterocyclic scaffolds, a novel series of 1,3,4-thiadiazole-1,3,4-oxadiazole-acetamide derivatives (7a – j) was designed and synthesized using molecular hybridization. The inhibitory effects of the target compounds on elastase were evaluated, and all of these molecules were found to be potent inhibitors compared to the standard reference oleanolic acid. Compound 7f exhibited the excellent inhibitory activity (IC 50 = 0.06 ± 0.02 μM), which is 214-fold more active than oleanolic acid (IC 50 = 12.84 ± 0.45 μM). Kinetic analysis was also performed on the most potent compound (7f) to determine the mode of binding with the target enzyme, and it was discovered that 7f inhibits the enzyme in a competitive manner. Furthermore, the MTT assay method was used to assess their toxicity on the viability of B16F10 melanoma cell lines, and all compounds did not display any toxic effect on the cells even at high concentrations. The molecular docking studies of all compounds also justified with their good docking score and among them, compound 7f had a good conformational state with hydrogen bond interactions within the receptor binding pocket, which is consistent with the experimental inhibition studies. [ABSTRACT FROM AUTHOR]