Identification of coprogen B and its breakdown products from Histoplasma capsulatum

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Abstract
Fe added to a chemically defined liquid medium suppressed hydroxamic acid production at 37.degree. C by H. capsulatum. Four hydroxamic acids, HA-I, HA-II, HA-III and HA-IV, present in the low-Fe 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; 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 TLC, IR spectra and reactivity to ninhydrin, 3 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.