Natural hydroxyanthraquinoid pigments as potent food grade colorants: an overview

Natural pigments and colorants are widely used in the world in many industries such as textile dying, food processing or cosmetic manufacturing. Among the natural products of interest are various compounds belonging to carotenoids, anthocyanins, chlorophylls, melanins, betalains... The review emphasizes pigments with anthraquinoid skeleton and gives an overview on hydroxyanthraquinoids described in Nature, the first one ever published. Trends in consumption, production and regulation of natural food grade colorants are given, in the current global market. The second part focuses on the description of the chemical structures of the main anthraquinoid colouring compounds, their properties and their biosynthetic pathways. Main natural sources of such pigments are summarized, followed by discussion about toxicity and carcinogenicity observed in some cases. As a conclusion, current industrial applications of natural hydroxyanthraquinoids are described with two examples, carminic acid from an insect and Arpink red (TM) from a filamentous fungus.