A method for identifying a natural substance capable of complex formation with Ni 2+ , Cu 2+ and/or Fe 2+ ions, characterized by the following steps (a) providing an aqueous, alcoholic or aqueous-alcoholic extract containing a natural substance, wherein the used extract containing a natural substrate is a plant-based food extract obtained by extraction of one or more parts of a plant, which is/are suitable for human consumption, selected from the group consisting of stems, leaves, flowers, roots, seeds, fruits, (b) providing a device containing a stationary phase loaded with Ni 2+ , Cu 2+ and/or Fe 2+ ions, which is suitable for immobilized metal ion affinity chromatography (IMAC) (IMAC device), (c) passing the extract containing a natural substrate of step (a) through a device of step (b), such that an adsorption of the natural substance capable of complex formation with Ni 2+ , Cu 2+ and/or Fe 2+ ions onto the stationary phase of the IMAC device is obtained, (d) optionally, rinsing the stationary phase loaded with the natural substance capable of complex formation with Ni 2+ , Cu 2+ and/or Fe 2+ ions of the IMAC device of step (c) with a solvent selected from the group consisting of pure water, preferably ion-free water, and water-ethanol mixtures, (e) desorption of the natural substance from the stationary phase of the IMAC device of step (c) or step (d), preferably by passing a solution containing one or more desorbents through the IMAC device of step (c) or of step (d), (f) optionally, separation of the natural substance from the desorbent, (g) identification of the natural substance capable of complex formation with Ni 2+ , Cu 2+ and/or Fe 2+ ions, wherein the natural substance is not a protein and has a molecular weight of less than or equal to 1000 g/mol. (a) providing an aqueous, alcoholic or aqueous-alcoholic extract containing a natural substance, wherein the used extract containing a natural substrate is a plant-based food extract obtained by extraction of one or more parts of a plant, which is/are suitable for human consumption, selected from the group consisting of stems, leaves, flowers, roots, seeds, fruits, (b) providing a device containing a stationary phase loaded with Ni 2+ , Cu 2+ and/or Fe 2+ ions, which is suitable for immobilized metal ion affinity chromatography (IMAC) (IMAC device), (c) passing the extract containing a natural substrate of step (a) through a device of step (b), such that an adsorption of the natural substance capable of complex formation with Ni 2+ , Cu 2+ and/or Fe 2+ ions onto the stationary phase of the IMAC device is obtained, (d) optionally, rinsing the stationary phase loaded with the natural substance capable of complex formation with Ni 2+ , Cu 2+ and/or Fe 2+ ions of the IMAC device of step (c) with a solvent selected from the group consisting of pure water, preferably ion-free water, and water-ethanol mixtures, (e) desorption of the natural substance from the stationary phase of the IMAC device of step (c) or step (d), preferably by passing a solution containing one or more desorbents through the IMAC device of step (c) or of step (d), (f) optionally, separation of the natural substance from the desorbent, (g) identification of the natural substance capable of complex formation with Ni 2+ , Cu 2+ and/or Fe 2+ ions, wherein the natural substance is not a protein and has a molecular weight of less than or equal to 1000 g/mol. <EOS>