In this study, we applied steered molecular dynamics (SMD) simulations to investigate the unbinding mechanism of nine inhibitors of the enzyme cyclin-dependent kinase 5 (CDK5). The study had two major objectives: (i) to create a correlation between the unbinding force profiles and the inhibition activities of these compounds expressed as IC50 values; (ii) to investigate the unbinding mechanism and to reveal atomistic insights, which could help identify accessory binding sites and transient interactions. Overall, we carried out 1.35 μs of cumulative SMD simulations. We showed that SMD could qualitatively discriminate binders from nonbinders, while it failed to properly rank series of inhibitors, particularly when IC50 values were too similar. From a mechanistic standpoint, SMD provided useful insights related to transient and dynamical interactions, which could complement static description obtained by X-ray crystallography experiments. In conclusion, the present study represents a further step toward a systematic exploitation of SMD and other dynamical approaches in structure-based drug design and computational medicinal chemistry.

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J. Neurochem. (2009) 109, 744–754. Abstract Previous studies have reported that selective sigma‐1 agonists may improve cognitive abilities in experimental animals possibly via a cholinergic mechanism. However, the issue of a direct action on to sigma‐1 receptors in memory‐related brain areas has been much less investigated. The newly synthetised compound methyl(1R,2S/1S,2R)‐2‐[4‐hydroxy‐4‐phenylpiperidin‐1‐yl)methyl]‐1‐(4‐methylphenyl) cyclopropanecarboxylate [(±)‐PPCC] has recently been shown to possess high affinity for the sigma‐1 receptor where it specifically acts as an agonist. Here, the functional effects of (±)‐PPCC were investigated in rat models of mild or severe cognitive dysfunction based on a sub‐total (≤ 70–80%) or complete (≥ 90–95%) central cholinergic depletion induced by different doses of the selective immunotoxin 192 IgG‐saporin injected intraventricularly. At 5–6 weeks post‐surgery, the lesioned animals exhibited dose‐dependent deficits in reference memory, as assessed using the Morris water maze task, whereas working memory abilities, evaluated using the radial arm water maze task, appeared equally impaired in the two dose groups. Daily treatment with (±)‐PPCC significantly improved both reference and working memory performance in all lesioned animals but it did not affect intact or sham‐lesioned subjects. In a separate test, treatment with (±)‐PPCC reversed the learning deficits induced by the muscarinic receptor antagonist atropine sulphate in both control and mild‐lesioned rats. The effect was blocked in lesioned, but not normal animals by pre‐treatment with the sigma‐1 antagonist N‐[2‐(3,4‐dichlorophenyl)ethyl]‐N‐methyl‐2‐(dimethylamino)ethylamine. The results suggest that (±)‐PPCC may efficiently ameliorate perturbed cognitive abilities, and that these anti‐amnesic effects most probably occur via a direct interaction of the compound with sigma‐1 receptors.

The development of Tyrosinase inhibitors (TYRIs) could represent an efficacious strategy for pharmacological intervention on skin pathologies related to aberrant production of melanin. Based on in silico studies we designed and tested a library of twenty-four compounds bearing the 4-(4-fluorobenzyl) piperazin-1-yl]-fragment. As result, we identified several compounds with excellent inhibit effects at low micromolar concentration against TYR from Agaricus bisporus (TyM). Among them, compound 25 (IC 50 ¼ 0.96 mM) proved to be~20-fold more potent than the reference compound kojic acid (IC 50 ¼ 17.76 mM) having wide applications in the cosmetics and pharmaceutical industries. The mode of interaction of active inhibitor 25 was deciphered by means of crystallography as well as molecular docking and these results were consistent with kinetic experiments. Moreover, the identified compound 25 exhibited no considerable cytotoxicity and showed anti-melanogenic effects on B16F10 melanoma cells. Therefore, a combination of computational and biochemical approaches could represent a rational guidelines for further structural modification of this class of compounds as future anti-melanogenic agents.

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Juglans regia L. (common walnut) is a deciduous tree belonging to Juglandaceae family. Since ancient time, walnut was widely used in traditional medicine for its antioxidant, antidiabetic, antimicrobial, anti-inflammatory, anti-atherogenic and liver-protective effects. In this work, the antibacterial and anti-biofilm activities of walnuts pellicle extract against coagulase-negative staphylococci were evaluated. Qualitative chemical analysis was performed by the thin layer chromatography. UPLC-Ms/Ms was used to identify the chemical composition of J. regia extract. The total flavonoid and phenolic contents was determined by the Aluminium chloride and Folin-Ciocalteu methods, respectively. The extract showed antibacterial activity with MIC ranging from 3.60 to 461.75 µg/ml and MBC ranging from 461.75 to >461.75 µg/ml. Furthermore, it significantly reduced biofilm biomass and cell viability in a dose-dependent manner.Biological activities of J. regia extract may be due to its high flavonoid and phenolic contents. The obtained results are promising and they deserve further scientific investigations.

The aim of the present study was to investigate the biological profile of new substituted 1-phenyl-2-cyclopropylmethylamines. High affinity for both sigma subtypes was achieved when 4-phenylpiperidin-4-ol (4a-e) and 4-benzylpiperidine moieties were present (5a-e). (1R,2S/1S,2R)-2-[4-Hydroxy-4-phenylpiperidin-1-yl)methyl]-1-(4-methylphenyl)cyclopropanecarboxylate (4b) showed high affinity for the sigma1 sites (Ki = 1.5 nM) and the most favorable sigma1/sigma2 selectivity (Ki(sigma2)/Ki(sigma1) = 33.9). Binding affinity studies showed that 4b binding on N-methyl-d-aspartate (NMDA), dopaminergic (D1, D2, D3), muscarinic, histaminergic H1, adrenergic (alpha1, alpha2), serotoninergic (5-HT2A, 5-HT2C, 5-HT3, 5-HT4, 5-HT6), DA (DAT), and 5-HT (SERT) transporters was not significant. Interestingly, sigma ligands differently induced the expression of tissue transglutaminase (TG-2) in primary astroglial cell cultures. We suggest that 4b may act as a sigma1/sigma2 agonist and that the sigma ligands may modulate TG-2 differently.