Identification of coprogen B and its breakdown products from Histoplasma capsulatum

Iron added to a chemically defined liquid medium suppressed hydroxamic acid production at 37 degrees C by yeast cells of Histoplasma capsulatum. Four hydroxamic acids, HA-I, HA-II, HA-III, and HA-IV, present in the low-iron fluid after the culture of H. capsulatum were isolated by extraction and cation-exchange chromatography through cellulose phosphate (0.35% formic acid). Visible spectra of prepared ferrihydroxamates indicated that HA-II and HA-III were monohydroxamates, whereas HA-I and HA-IV were identified as di- and trihydroxamates, respectively. Reductive hydrolysis of HA-I (the major hydroxamic acid isolated) yielded ornithine. Hydrolysis of HA-IV in water or in 0.1 N NaOH resulted in the formation of HA-I (dihydroxamic acid) and HA-II (monohydroxamic acid). Based on their charge at pH 5.2 and 2 determined by paper electrophoresis, Rf values on thin-layer chromatography, infrared spectra, and reactivity to ninhydrin, three of the isolated hydroxamic acids were identified as deferricoprogen B (HA-IV) and its breakdown products, dimerumic acid (HA-I) and trans fusarinine (HA-II). HA-I and HA-IV exhibited growth factor activity for both yeast and mycelial forms of growth of H. capsulatum.