Indole is an important compound in nature and is present in many pathways. First, an overview is given on the oxidative conversions of indole and respective products formed. A focus is put on the formation of pure indigo and some derivatives. Thus, flavin-dependent monooxygenases (styrene epoxidases) were employed which allow the selective oxygenation of indole leading to pure products without the formation of by-pro - ducts as indirubin or isoindigo.