Abstract
Allium genus (Amaryllidaceae) is widely distributed in the Northern hemisphere. Some species, including garlic and onion, have been used since ancient times as both food ingredients and medicinal plants. Many reviews deal with the chemical constituents, particularly the typical sulfur compounds, as well as with Allium pharmacological properties, such as antimicrobial, anti-inflammatory, antioxidant, and cytotoxic activities. The bibliographic search performed in this review is mainly focused on the potential role of Allium species in inhibiting melanogenesis, which has been mainly assessed through the evaluation of the inhibitory properties on tyrosinase, the key enzyme in melanin biosynthesis. Two well established models for identifying potential skin-whitening agents have been used to assess the anti-melanogenic effects of Allium species, the mushroom tyrosinase and the murine melanoma B16 cell line. Here, a literature search from Scopus, Web of Science, and PubMed databases has been performed using the keywords "Allium", "tyrosinase", "anti-melanogenic", and "melanogenesis", combined by means of Boolean operators. Based on selected inclusion criteria, 32 eligible papers have been selected. The aim of this systematic review is to offer an overview of the species for which the ability to affect melanogenesis has been demonstrated to date, highlighting a new and emerging perspective on the potential therapeutic use of Allium species. The biological properties of isolated pure compounds and the negative outcomes have been also considered.