Methylene blue (MB) is used extensively in medicine; nevertheless, excessive dosages (>= 7 mg/kg) of MB can oxidize hemoglobin directly, resulting in methemoglobinemia. Especially in newborns, hemolysis is linked to doses of >15 mg/kg. It may also impede the clinical manifestations of cyanosis and discolor mucosal membranes and secretions. In this work, iron oxide nanoparticles (Fe(2)O(3)NPs) were synthesized utilizing green chemistry methods using fresh leaves of red cabbage (Brassica oleracea L. var. capitata f, rubra) extract and calcined at 700 degrees C temperatures to get the hematite phases. In this approach, biomolecules such as alkaloids, steroids, flavonoids, terpenoids, phenolic, flavonoids, anthocyanins, and glucosinolates presence in the red cabbage extract have been shown to work as encapsulating agents for Fe(2)O(3)NPs. The various physical and chemical characteristics of synthesized Fe(2)O(3)NPs with spherical solid shapes and having a diameter ranging from 29.03 to 49.13 nm were characterized using FESEM, TEM, XRD, FTIR, and UV-visible spectroscopy techniques. The photocatalytic activity of synthesized Fe(2)O(3)NPs was tested against methylene blue (MB) under UV-visible light. The photocatalyst degraded approximately 65.5 % of the original MB dye at a rate of 0.0043 min(-1) during 240 min of irradiation.