The Heptacarboxylic Porphyrin of Various Types of Porphyria and the Melting-Point Curve of Methyl Esters of the I and III Isomers

Abstract The heptacarboxylic porphyrin (hepta) isolated from different types of porphyric urine samples contains different proportions of the isomers I and III. These were separated chromatographically. The hepta in congenital porphyria was found to contain 65% of Type I isomer and 35% of Type III; that in acute intermittent porphyria, 70-80% III and 20-30% I; and that in porphyria cutanea tarda, 80-90% III. Several other cases including 1 of coproporphyria, 1 of South African genetic porphyria, 1 of Bantu porphyria, 4 of hexachlorobenzene poisoning in Turkish individuals were also examined. From the X-ray diffraction pattern and long-column chromatography, the Hepta III prepared either from decarboxylation of Uroporphyrin III or by condensation of porphobilinogen revealed a more complex configuration than that isolated from porphyric materials. The natural hepta might be dominated by one of the four possible isomers of the III series. A melting-point composition curve of methyl esters of Hepta I and III was constructed, and its applicability was tested. The identity of the hepta isolated in porphyria cutanea tarda with "208" and "pseudouro" porphyrins is discussed, and the name "cutano-porphyrin" suggested.