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    Anti-oxidant and tyrosinase inhibitory in vitro activity of amino acids and small peptides: new hints for the multifaceted treatment of neurologic and metabolic disfunctions
    (MDPI, 2019) Luisi, Grazia; Stefanucci, Azzurra; Zengin, Gökhan; Dimmito, Marilisa Pia; Mollica, Adriano
    Oxidative damage is among the factors associated with the onset of chronic pathologies, such as neurodegenerative and metabolic diseases. Several classes of anti-oxidant compounds have been suggested as having a protective role against cellular stressors, but, in this perspective, peptides' world represents a poorly explored source. In the present study, the free radical scavenging properties, the metal ion reducing power, and the metal chelating activity of a series of sulfurated amino acids and tripeptides were determined in vitro through canonical assays (DPPH, ABTS, CUPRAC, FRAP, PM, and EECC) and estimated in comparison with the corresponding activities of synthetic peptide semicarbazones, incorporating the peculiar non-proteinogenic amino acid, tert-leucine (tLeu). The compounds exhibited remarkable anti-oxidant properties. As expected, sulfurated compounds 1-5 were found to be the most efficient radical scavengers and strongest reductants. Nevertheless, tLeu-containing peptides 7 and 8 disclosed notable metal reducing and chelating activities. These unprecedented results indicate that tLeu-featuring di- and tripeptide backbones, bearing the semicarbazone chelating moiety, are compatible with the emergence of an anti-oxidant potential. Additionally, when tested against a panel of enzymes usually targeted for therapeutic purposes in neurodegenerative and metabolic disorders, all samples were found to be good inhibitors of tyrosinase.
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    Combinatorial peptide library screening for discovery of diverse alpha-glucosidase inhibitors using molecular dynamics simulations and binary QSAR models
    (TAYLOR & FRANCIS INC, 2019) Mollica, Adriano; Zengin, Gökhan; Durdağı, Serdar; Salmas, Ramin Ekhteiari; Macedonio, Giorgia; Stefanucci, Azzurra; Dimmito, Marilisa Pia; Novellino, Ettore
    Human alpha-glucosidase is an enzyme involved in the catalytic cleavage of the glucoside bond and involved in numerous functionalities of the organism, as well as in the insurgence of diabetes mellitus 2 and obesity. Thus, developing chemicals that inhibit this enzyme is a promising approach for the treatment of several pathologies. Small peptides such as di- and tri-peptides may be in natural organism as well as in the GI tract in high concentration, coming from the digestive process of meat, wheat and milk proteins. In this work, we reported the first tentative hierarchical structure-based virtual screening of peptides for human alpha-glucosidase. The goal of this work is to discover novel and diverse lead compounds that my act as inhibitors of alpha-glucosidase such as small peptides by performing a computer aided virtual screening and to find novel scaffolds for further development. Thus, in order to select novel candidates with original structure we performed molecular dynamics (MD) simulations among the 12 top-ranked peptides taking as comparison the MD simulations performed on crystallographic inhibitor acarbose. The compounds with the lower RMSD variability during the MD, were reserved for in vitro biological assay. The selected 4 promising structures were prepared on solid phase peptide synthesis and used for the inhibitory assay, among them compound 2 showed good inhibitory activity, which validated our method as an original strategy to discover novel peptide inhibitors. Moreover, pharmacokinetic profile predictions of these 4 peptides were also carried out with binary QSAR models using MetaCore/MetaDrug applications.
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    Discovery of kynurenines containing oligopeptides as potent opioid receptor agonists
    (MDPI AG, 2020) Szucs, Edina; Stefanucci, Azzurra; Dimmito, Marilisa Pia; Zádor, Ferenc; Pieretti, Stefano; Zengin, Gökhan; Vécsei, László
    Kynurenine (kyn) and kynurenic acid (kyna) are well-defined metabolites of tryptophan catabolism collectively known as “kynurenines”, which exert regulatory functions in host-microbiome signaling, immune cell response, and neuronal excitability. Kynurenine containing peptides endowed with opioid receptor activity have been isolated from natural organisms; thus, in this work, novel opioid peptide analogs incorporating L-kynurenine (L-kyn) and kynurenic acid (kyna) in place of native amino acids have been designed and synthesized with the aim to investigate the biological effect of these modifications. The kyna-containing peptide (KA1) binds selectively the ?-opioid receptor with a Ki = 1.08 ± 0.26 (selectivity ratio ?/?/? = 1:514:10000), while the L-kyn-containing peptide (K6) shows a mixed binding affinity for ?, ?, and ?-opioid receptors, with efficacy and potency (Emax = 209.7 + 3.4%; LogEC50 = ?5.984 + 0.054) higher than those of the reference compound DAMGO. This novel oligopeptide exhibits a strong antinociceptive effect after i.c.v. and s.c. administrations in in vivo tests, according to good stability in human plasma (t1/2 = 47 min). © 2020 by the authors. Licensee MDPI, Basel, Switzerland.
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    Discovery of novel µ-opioid receptor inverse agonist from a combinatorial library of tetrapeptides through structure-based virtual screening
    (MDPI, 2019) Poli, Giulio; Dimmito, Marilisa Pia; Mollica, Adriano; Zengin, Gökhan; Benyhe, Sandor; Zador, Ferenc; Stefanucci, Azzurra
    Morphine, oxycodone, fentanyl, and other mu-opioid receptors (MOR) agonists have been used for decades in antinociceptive therapies. However, these drugs are associated with numerous side effects, such as euphoria, addiction, respiratory depression, and adverse gastrointestinal reactions, thus, circumventing these drawbacks is of extensive importance. With the aim of identifying novel peptide ligands endowed with MOR inhibitory activity, we developed a virtual screening protocol, including receptor-based pharmacophore screening, docking studies, and molecular dynamics simulations, which was used to filter an in-house built virtual library of tetrapeptide ligands. The three top-scored compounds were synthesized and subjected to biological evaluation, revealing the identity of a hit compound (peptide 1) endowed with appreciable MOR inverse agonist effect and selectivity over delta-opioid receptors. These results confirmed the reliability of our computational approach and provided a promising starting point for the development of new potent MOR modulators.