The Synthetic Approaches for Preparation of Indigo and Applications in Denim Industry

This paper describes indigo chemistry and its brief scientific history beginning with the first characterization and chemical synthesis of indigo via various precursors such as isatin, cinnamic acid, 2-nitrobenzaldehyde, anthranilic acid, N-phenylglycine, aniline, and indole. Furthermore, alternative methods such as eco-friendly microbial synthesis of indigo using a variety of enzymes are reported: Cytochrome P450 monooxygenases, flavin-containing monooxygenases, and unspecific peroxygenases. Subsequently, the application of indigo in the denim industry, reduction methods (chemical, electrochemical, enzymatic and catalytic) and dyeing methods (all parameters in dyeing, ring dye) are discussed. In addition, the main reason for the use of indigo in the denim industry is briefly explained.