An iron complex, "astechrome," was isolated from Aspergillus terreus IFO 6123, and its structure was determined. When the fungus was cultivated with shaking (using Czapek-Dox medium containing polypeptone and ferrous ion, which was found to be the best culture medium), astechrome was obtained instead of the previously reported antitumor metabolite asterriquinone. The compound was purified from the mycelia via solvent extraction and chromatography. Structural analysis through spectral techniques (field desorption mass spectroscopy, elemental analysis, atomic absorption spectrometry), chemical reactions (catalytic hydrogenation, iron removal with alkali, reaction with phosphorus tribromide), and derivative preparation (e.g., copper complex, methylated derivatives) revealed that astechrome is an Fe³⁺ complex with three identical ligands containing a hydroxamic acid moiety, with the molecular formula (C₂₀H₂₂N₃O₃)₃Fe. The iron was tightly bound to the ligand and could not be easily removed by chelating agents. Astechrome was neutral, optically inactive, and showed weak antibiotic activity but no antitumor activity against Ehrlich ascites carcinoma.