Résumé
In the plant kingdom, numerous pigments have already been identified, but only a minority of them is allowed by legal regulations for textile dyeing, food coloring or cosmetic and pharmaceutics’ manufacturing. Anthraquinones, produced as secondary metabolites in plants, constitute a large structural variety of compounds among the quinone family. Derivatives that contain hydroxyl groups, namely hydroxy-anthraquinones, are colored. They have attracted the attention of many researchers due to their large spectrum of possible applications especially in the fields of dyeing. These dyes produce a wide range of nuances in shades (red, orange and yellow). Fifteen anthraquinones’ derivatives from madder color roots (Rubia tinctorium L.) play an important role in dyeing (CI Natural Red 8). Purpurin (CI Natural Red 16) is a minor component in the madder color, but is the main dye in addition with munjistin in Indian madder (Rubia cordifolia). Alizarin (Pigment Red 83, CI Mordant Red 11) is the main red dye in madder color. Several other species, although producing hydroxyanthraquinones dyes, are not considered viable contributors to the natural red dye market. This is the case of Anchusa tinctoria, Lithospermum spp., Carthamus tinctoria or Galium species. Some hydroxyanthraquinone dyes, either extracted from insects (carminic acid), microbes (Arpink red) or plants (alizarin from European madder roots), are already manufactured and marketed as natural colorants in textile, food, cosmetic or pharmaceutics industries. As these dyes are not yet widely applied, research work need to extend the knowledge concerning their potential roles on human health. Their positive and/or negative effects due to the 9,10-anthracenedione structure and its substituents are still not clearly understood and their potential role or effect on human health is currently being discussed by scientists. For example, rubiadin, lucidin, and more generally madder color, can induce carcinogenicity and should be dealt carefully as a significant carcinogen. In contrast, numerous pharmacological studies have proved that some hydroxyanthraquinones have positive effects. Examples including emodin, rhein, physcion, damnacanthal, purpurin, which can inhibit proliferation of various cancer cells. This work gives an overview on hydroxyanthraquinone dyes described in plants.