Contents lists available at ScienceDirect Bioorganic Chemistry journal homepage: www.elsevier.com/locate/bioorg Coumaric acid derivatives as tyrosinase inhibitors: Efcacy studies through in silico, in vitro and ex vivo approaches Marina Themoteo Varela a,1 , Márcio Ferrarini a,1 , Vitória Gallo Mercaldi a , Bianca da Silva Suf b , Giovana Padovani b , Lucas Idacir Sbrugnera Nazato b , João Paulo S. Fernandes a, ⁎ a Department of Pharmaceutical Sciences, Institute of Environmental, Chemical and Pharmaceutical Sciences, Universidade Federal de São Paulo, Rua São Nicolau 210, 09913-030 Diadema-SP, Brazil b Research and Development Department, Chemyunion Química Ltda, Av. Independência 1501, 18087-101 Sorocaba-SP, Brazil ARTICLE INFO Keywords: Coumaric acid ester Tyrosinase inhibitor Antimelanogenic agent Melanin synthesis inhibitor Molecular docking ABSTRACT p-Coumaric acid is a known inhibitor of tyrosinase, an enzyme involved in the initial steps of the melanin synthesis in human and other species. However, its low lipophilicity impairs its penetration through skin and efcacy as antimelanogenic agent indeed. Accordingly, this paper reports the assessment of several coumaric acid derivatives as tyrosinase inhibitors and antimelanogenic agents in in vitro, in silico and ex vivo assays. The compounds were designed with modifcations in the aromatic and acid moieties of p-coumaric acid, being the coumarate esters the most promising derivatives. The compounds showed higher tyrosinase inhibitory activity (pIC 50 3.7–4.2) than the parent acid, being compounds 1d, 1e and 1f the most potent inhibitors. Docking analysis showed that these esters are competitive inhibitors per se, and act independently of a redox mechanism as suggested by DPPH assays. Moreover, the esters showed efcacy in reducing the melanin deposition in human skin fragments at 0.1% concentration, especially compound 1e. In summary, there is an important equilibria between tyrosinase afnity and lipophilicity that must be considered to get efective antimelanogenic agents with adequate permeability in the skin. 1. Introduction Melanin biosynthesis is a natural process that occurs in several living species, including plants, fungi and mammals. The limiting step in melanogenesis is controlled by metalloprotein tyrosinase, a copper- containing polyphenol oxidase that oxidizes L-tyrosine and L-DOPA into DOPA-quinone (Fig. 1) [1]. The biological importance of melanin is variable in each organism, but are mostly related to photoprotection from UV light and pigmentation. In humans, melanin is responsible for the diferent eye, hair and skin colors, as well as neural pigmentation, associated with neuromelanin [2]. Many dysfunctions and pathologies may come as a result of the excess or lacking melanin pigments produced in the cells. Albinism is a genetic disorder that is characterized by alteration of TYR gene, re- sponsible for controlling the presence of tyrosinase in cells [3]. This alteration causes cells to be unable to produce melanin, giving to the individuals the characteristic pale skin and pink/red eyes and white hair. Excessive production of melanin is usually caused by prolonged and continuous sun exposure and also after infammation processes in the skin, such as acne [4]. Tyrosinase is an enzyme present in several organisms, including plant, fungal and animal species, but with marked diferences among them. For instance, human tyrosinase is an intracellular membrane- bound glycoprotein [5], while fungal tyrosinase is a soluble enzyme. Although the tyrosinases from diferent species difer considerably re- garding several aspects of the protein structure, they share in common a similar active site, comprised by two copper atoms coordinated by three histidine residues, which catalyzes the oxidation reaction of phenols [6,7]. Mushroom tyrosinase is a widely used model for identifying tyr- osinase inhibitors for human applications, since it is an accessible, commercially available enzyme due to its soluble characteristic [8,9]. Moreover, known inhibitors of mushroom tyrosinase usually exhibit increased potency in murine and human tyrosinases, and thus by identifying novel inhibitors in mushroom tyrosinase model, really ef- fective antimelanogenic compounds may be expected [10,11]. There are many applications of melanin biosynthesis inhibitors in both pharmacological and cosmetic aspects, especially to treat https://doi.org/10.1016/j.bioorg.2020.104108 Received 11 May 2020; Received in revised form 23 May 2020; Accepted 15 July 2020 ⁎ Corresponding author at: Department of Pharmaceutical Sciences, Universidade Federal de São Paulo, Rua São Nicolau 210, 09913-030 Diadema-SP, Brazil. E-mail address: joao.fernandes@unifesp.br (J.P.S. Fernandes). 1 These authors contributed equally. Bioorganic Chemistry 103 (2020) 104108 Available online 21 July 2020 0045-2068/ © 2020 Elsevier Inc. All rights reserved. T