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      Evaluation of novel pyrimidine derivatives as a new class of mushroom tyrosinase inhibitor

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          Background and aim

          Tyrosinase (EC is responsible for enzymatic browning in fruits and vegetables. Its inhibitors may be applied to efficiently treat hyperpigmentation and are widely used in pharmaceutical and cosmetic products, food supplements and insecticides. Previous studies have shown that heterocyclic compounds with an amino group can inhibit tyrosinase activity. The present study aims to evaluate the inhibitory effect of some novel 2,6-diamino-4-chloropyrimidine derivatives (1a-e) and 2,4,6-triaminopyrimidine (2a–e) including bioactive aniline moiety on the activity of the mushroom tyrosinase.


          In practice, the azo salt was initially synthesized from aniline derivatives and combined subsequently with the 2,4,6-triaminopyrimidine and 2,6-diamino-4 chloropyrimidine followed by crystallization. The structures of resulting compounds were confirmed by FT-IR, 13C NMR, and 1H NMR. The derivatives (0–100 µM) were evaluated for their inhibitory effect on tyrosinase activity using l-3,4-dihydroxyphenylalanine (l-DOPA) as substrate.


          All compounds showed inhibitory effects against the activity of the enzyme. About 23.72–55.08% inhibition was observed in the presence of 30 µM of each compound. The IC 50 values of the synthesized compounds were measured, and their inhibition properties were also visualized by zymography. Based on the results, the compounds 1a-e and 2a-e showed moderate inhibitory activities. Notably, pyrimidine derivatives 1a (IC 50=24.68) and 1d (IC 50=24.45) also exhibited similar inhibitory activities when compared with the positive control, kojic acid (IC 50=25.24 µM). Kinetic studies indicated that the type of inhibition was noncompetitive.


          All results suggest that pyrimidine derivatives, especially 1d and 1a, can be considered as safe and efficient tyrosinase inhibitors.

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          Most cited references 22

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          Crystal structure of Agaricus bisporus mushroom tyrosinase: identity of the tetramer subunits and interaction with tropolone.

          Tyrosinase catalyzes the conversion of phenolic compounds into their quinone derivatives, which are precursors for the formation of melanin, a ubiquitous pigment in living organisms. Because of its importance for browning reactions in the food industry, the tyrosinase from the mushroom Agaricus bisporus has been investigated in depth. In previous studies the tyrosinase enzyme complex was shown to be a H(2)L(2) tetramer, but no clues were obtained of the identities of the subunits, their mode of association, and the 3D structure of the complex. Here we unravel this tetramer at the molecular level. Its 2.3 Å resolution crystal structure is the first structure of the full fungal tyrosinase complex. The complex comprises two H subunits of ∼392 residues and two L subunits of ∼150 residues. The H subunit originates from the ppo3 gene and has a fold similar to other tyrosinases, but it is ∼100 residues larger. The L subunit appeared to be the product of orf239342 and has a lectin-like fold. The H subunit contains a binuclear copper-binding site in the deoxy-state, in which three histidine residues coordinate each copper ion. The side chains of these histidines have their orientation fixed by hydrogen bonds or, in the case of His85, by a thioether bridge with the side chain of Cys83. The specific tyrosinase inhibitor tropolone forms a pre-Michaelis complex with the enzyme. It binds near the binuclear copper site without directly coordinating the copper ions. The function of the ORF239342 subunits is not known. Carbohydrate binding sites identified in other lectins are not conserved in ORF239342, and the subunits are over 25 Å away from the active site, making a role in activity unlikely. The structures explain how calcium ions stabilize the tetrameric state of the enzyme.
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            Naturally occurring tyrosinase inhibitors: mechanism and applications in skin health, cosmetics and agriculture industries.

            Tyrosinase is a copper-containing enzyme, which is widely distributed in microorganisms, animals and plants and is a key enzyme in melanin biosynthesis, involved in determining the color of mammalian skin and hair. In addition, unfavorable enzymatic browning of plant-derived foods by tyrosinase causes a decrease in nutritional quality and economic loss of food products. The inadequacy of current conventional methods to prevent tyrosinase action encourages researchers to seek new potent tyrosinase inhibitors for food and cosmetics. This article presents a study on the importance of tyrosinase, biochemical characteristics, type of inhibitions, activators from various natural sources with its clinical and industrial importance in recent prospects is discussed in this paper.
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              EADock: docking of small molecules into protein active sites with a multiobjective evolutionary optimization.

              In recent years, protein-ligand docking has become a powerful tool for drug development. Although several approaches suitable for high throughput screening are available, there is a need for methods able to identify binding modes with high accuracy. This accuracy is essential to reliably compute the binding free energy of the ligand. Such methods are needed when the binding mode of lead compounds is not determined experimentally but is needed for structure-based lead optimization. We present here a new docking software, called EADock, that aims at this goal. It uses an hybrid evolutionary algorithm with two fitness functions, in combination with a sophisticated management of the diversity. EADock is interfaced with the CHARMM package for energy calculations and coordinate handling. A validation was carried out on 37 crystallized protein-ligand complexes featuring 11 different proteins. The search space was defined as a sphere of 15 A around the center of mass of the ligand position in the crystal structure, and on the contrary to other benchmarks, our algorithm was fed with optimized ligand positions up to 10 A root mean square deviation (RMSD) from the crystal structure, excluding the latter. This validation illustrates the efficiency of our sampling strategy, as correct binding modes, defined by a RMSD to the crystal structure lower than 2 A, were identified and ranked first for 68% of the complexes. The success rate increases to 78% when considering the five best ranked clusters, and 92% when all clusters present in the last generation are taken into account. Most failures could be explained by the presence of crystal contacts in the experimental structure. Finally, the ability of EADock to accurately predict binding modes on a real application was illustrated by the successful docking of the RGD cyclic pentapeptide on the alphaVbeta3 integrin, starting far away from the binding pocket. 2007 Wiley-Liss, Inc.

                Author and article information

                Drug Des Devel Ther
                Drug Des Devel Ther
                Drug Design, Development and Therapy
                08 July 2019
                : 13
                : 2169-2178
                [1 ] Department of Biology, Faculty of Sciences, University of Guilan , Rasht, Iran
                [2 ] Department of Chemistry, Faculty of Sciences, University of Guilan , Rasht, Iran
                Author notes
                Correspondence: Hossein GhafouriDepartment of Biology, Faculty of Sciences, University of Guilan, Namjoo Ave, P.O. Box 41335-1914 , Rasht, IranTel/Fax +98 133 333 3647Email h.ghafoori@ 123456guilan.ac.ir
                © 2019 Mirmortazavi et al.

                This work is published and licensed by Dove Medical Press Limited. The full terms of this license are available at https://www.dovepress.com/terms.php and incorporate the Creative Commons Attribution – Non Commercial (unported, v3.0) License ( http://creativecommons.org/licenses/by-nc/3.0/). By accessing the work you hereby accept the Terms. Non-commercial uses of the work are permitted without any further permission from Dove Medical Press Limited, provided the work is properly attributed. For permission for commercial use of this work, please see paragraphs 4.2 and 5 of our Terms ( https://www.dovepress.com/terms.php).

                Page count
                Figures: 7, Tables: 2, References: 29, Pages: 10
                Original Research


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