Short communication Hesperetin induces melanin production in adult human epidermal melanocytes Iris Usach a,1 , Raquel Taléns-Visconti a,1 , Lorena Magraner-Pardo b , José-Esteban Peris a, * a Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, University of Valencia, Avda. V. Andrés Estellés, s/n, Burjassot, Valencia 46100, Spain b Fundación Centro de Innovación y Demostración Tecnológica, Paseo de la Castellana, 141, Madrid 28046, Spain ARTICLE INFO Article history: Received 30 December 2014 Accepted 23 February 2015 Available online 9 March 2015 Keywords: Hesperetin Melanogenesis Human melanocytes A B ST R AC T One of the major sources of flavonoids for humans are citrus fruits, hesperidin being the predominant flavonoid. Hesperetin (HSP), the aglycon of hesperidin, has been reported to provide health benefits such as antioxidant, anti-inflammatory and anticarcinogenic effects. However, the effect of HSP on skin pig- mentation is not clear. Some authors have found that HSP induces melanogenesis in murine B16-F10 melanoma cells, which, if extrapolated to in vivo conditions, might protect skin against photodamage. Since the effect of HSP on normal melanocytes could be different to that observed on melanoma cells, the described effect of HSP on murine melanoma cells has been compared to the effect obtained using normal human melanocytes. HSP concentrations of 25 and 50 μM induced melanin synthesis and ty- rosinase activity in human melanocytes in a concentration-dependent manner. Compared to control melanocytes, 25 μM HSP increased melanin production and tyrosinase activity 1.4-fold (p < 0.01) and 1.1-fold (p < 0.01), respectively, and the corresponding increases in the case of 50μM HSP were 1.9-fold (p < 0.001) and 1.3-fold (p < 0.001). Therefore, HSP could be considered a valuable photoprotective substance if its capacity to increase melanin production in human melanocyte cultures could be reproduced on human skin. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Human skin pigmentation has many valuable functions, the most important being its role in photoprotection due to its ability to absorb ultraviolet radiation (Costin and Hearing, 2007; Lin and Fisher, 2007; Park et al., 2009). Melanogenesis is the process responsible for cutaneous synthesis and the distribution of the pigment melanin, which is stimulated by many intrinsic and extrinsic regulation factors, such as ultraviolet radiation and the melanocyte-stimulating hormone (α-MSH). Melanin is synthetized by melanocytes via an enzymatic cascade leading to the conversion of tyrosine to melanin pigment, and one of the key enzymes in this process is tyrosinase, which is considered the rate-limiting enzyme for controlling the production of melanin. Enzymatic components of melanosomes include tyrosinase, tyrosinase-related protein 1 and DOPAchrome tautomerase. Phenotypic diversity of skin pigmentation is closely related to the variation in the number, size, composition and dis- tribution of melanosomes, whereas melanocyte numbers typically remain relatively constant (Lin and Fisher, 2007). A great deal of research has recently focused on the potential use of flavonoids to prevent photodamage. Hesperetin (HSP, 3′,5,7-trihydroxy-4′-methoxyflavanone) belongs to the flavanone sub- class of flavonoids, one of the largest groups of phenolic plant constituents. HSP is the aglycone of hesperidin, the predominant flavonoid found in citrus fruits (Nielsen et al., 2006). The chemical structure, molecular formula and molecular weight of HSP is shown in Fig. 1. HSP has been reported to possess many beneficial effects due to its antioxidant (Choi, 2008; Kim et al., 2004; Pollard et al., 2006), anticarcinogenic (Aranganathan and Nalini, 2009; Li et al., 2013; Yang et al., 2013), anti-inflammatory (Hirata et al., 2005), neuroprotective (Huang et al., 2012a) and cardioprotective (Trivedi et al., 2011) properties. Moreover, HSP is hypolipidemic (Morin et al., 2008), platelet-aggregation-inhibitory (Jin et al., 2007) and effec- tive in attenuating airway hyperresponsiveness (Shih et al., 2012). However, the effect of HSP on skin pigmentation is not clear. Some authors have described a whitening effect of HSP when applied on the skin of laboratory animals (Huang et al., 2010; Tsai et al., 2010), while others have found that HSP induces melanogenesis in murine melanoma cells when added to the culture medium (Huang Abbreviations: α-MSH, melanocyte-stimulating hormone; DMSO, dimethylsulf- oxide; HEMa, Hightly pigmented adult human epidermal melanocytes; HSP, Hesperetin; L-DOPA, 3,4-dihydroxy-L-phenyalanine; MITF, microphthalmia- associated transcription factor; PBS, phosphate-buffered saline. * Corresponding author. Department of Pharmacy and Pharmaceutical Technology, Faculty of Pharmacy, University of Valencia, Avda. V. Andrés Estellés, s/n, Burjassot, Valencia 46100, Spain. Tel.: +34 963543353; fax: +34 963544911. E-mail address: jose.e.peris@uv.es (J.-E. Peris). 1 These authors contributed equally to this work. http://dx.doi.org/10.1016/j.fct.2015.02.017 0278-6915/© 2015 Elsevier Ltd. All rights reserved. Food and Chemical Toxicology 80 (2015) 80–84 Contents lists available at ScienceDirect Food and Chemical Toxicology journal homepage: www.elsevier.com/locate/foodchemtox