Isolation and characterization of beta-hydroxypropionic acid- and hydroxyacetic acid-uroporphyrin I in the urine of a patient with congenital erythropoietic porphyria by high performance liquid chromatography and liquid secondary ion mass spectrometry

Dihydroxy-, Hydroxyspirolactone-, and Dihydroxyspirolactone-urochlorins Induced by 2,3,7,8-Tetrachlorodibenzo-p-dioxin in the Liver of Mice

Previous work has shown that 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) causes porphyria, enhanced by iron, in C57BL/6J mice with marked accumulation in the liver of uroporphyrin I and III isomers and heptacarboxylic acid III and is one model of human porphyria cutanea tarda. Preliminary examination by HPLC also indicated the presence of some oxygenated side chain uroporphyrin derivatives. Here, the porphyrin constituents of TCDD-induced porphyric liver have been examined by HPLC/electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC/ESI-Q-TOFMS) to characterize the major and minor porphyrins present in hepatic tissue. As well as the major constituents uroporphyrins I and III, we identified the isomers of heptacarboxylic, hexacarboxylic, and pentacarboxylic acid porphyrins arising from intermediates in the stepwise decarboxylation of uroporphyrinogen I and III to coproporphyrinogens. In addition, monohydroxy analogues of uroporphyrin isomers were detected hydroxylated in the acetic acid and beta-positions of propionic acid side chains and in the meso ring position. Of particular note, for the first time for human and experimental porphyrias, we found chlorins (dihydroxy-, hydroxyspirolactone- ,and dihydroxyspirolactone-urochlorins) consistent with those derived from an epoxyurochlorin structure, formed by oxidation of the double bond of a pyrrole ring of uroporphyrinogen I and III isomers. The findings demonstrate that oxygen insertion into the pyrrole rings of uroporphyrinogens occurs under pathological circumstances in vivo and support the evidence for an oxidative cellular environment present in TCDD-treated porphyric tissue.

Analysis of urinary and faecal porphyrin excretion patterns in human porphyrias by fast atom bombardment mass spectrometry

We report a new method for obtaining urinary and faecal porphyrin excretion patterns in human porphyrias based on fast atom bombardment mass spectrometry (FAB-MS). Porphyrins were esterified and extracted from urine or faeces as their methyl esters for analysis by FAB-MS. The protonated pseudo-molecular ion [M + H]+ observed for each porphyrin is characteristic of that porphyrin, thus allowing a mixture of porphyrins to be analysed without the need for chromatographic separation. By using tandem MS, identification and characterisation of unknown porphyrins can be achieved. The urinary and faecal porphyrin excretion patterns from various porphyric patients obtained by FAB-MS are in good agreement with those analysed by TLC or HPLC methods.

Peroxylated and hydroxylated uroporphyrins: a study of their production in vitro in enzymic and chemical model systems

In previous work certain hydroxylated and peroxylated derivatives of uroporphyrin (URO) have been isolated from the urine of patients suffering from porphyria. We have now investigated the mechanism of production of these oxygenated derivatives of URO, using both enzymic and chemical model systems and also the effect of exposure to light during reoxidation of uroporphyrinogen (URO'gen). When URO'gen was incubated with haemolysates, peaks with the same retention times as peroxyacetic acid URO, meso-hydroxy URO and beta-hydroxypropionic acid URO were all detected. The first of these was formed in sufficient amounts to allow its characterization by mass spectrometry. Under these conditions, peroxyacetic acid derivatives of heptacarboxylate and pentacarboxylate porphyrins could also be produced from the corresponding porphyrinogens, but no peroxylated product could be obtained from coproporphyrinogen (COPRO'gen, where no acetic acid side chains are present) or from the fully oxidized URO. Similar results were obtained on re-oxidation of URO'gen in the xanthine oxidase-xanthine system and in the presence of hydrogen peroxide/Fe-EDTA (ethylenediamine-tetraacetic acid) and here again no peroxylated product could be detected from either COPRO'gen or URO. Finally, formation of peroxyacetic acid URO could be demonstrated during photo-oxidation of URO'gen and this was followed by light-induced loss of both URO and its peroxylated derivative. It is concluded that the oxygenated derivatives arise from the action of reactive oxygen species on the porphyrinogens (rather than the porphyrins), with one of the acetic acid side chain serving as the preferential (or exclusive target) for peroxylation.

Isolation and characterization of new porphyrin metabolites in human porphyria cutanea tarda and in rats treated with hexachlorobenzene by HPTLC, HPLC and liquid secondary ion mass spectrometry

Porphyrin metabolisms in human porphyria cutanea tarda (PCT) and in rats treated with hexachlorobenzene (HCB) have been studied in detail by high performance thin layer chromatography (HPTLC), high performance liquid chromatography (HPLC) and liquid secondary ion mass spectrometry (LSIMS). The analyses of porphyrin metabolites in the urine, faeces and liver biopsies of patients with PCT have shown that apart from uroporphyrin I and III and their expected decarboxylation intermediates and products, a complex mixture of many other porphyrins are present. The new porphyrins identified are: meso-hydroxyuroporphyrin III, beta-hydroxypropionic acid uroporphyrin III, hydroxyacetic acid uroporphyrin III, peroxyacetic acid uroporphyrin III, beta-hydroxyproionic acid heptacarboxylic acid porphyrin III, hydroxyacetic acid hepatocarboxylic porphyrin III and peroxyacetic acid pentacarboxylic porphyrin III.

Determination of hydroxy and peroxy acid derivatives of uroporphyrin in the plasma of patients with congenital erythropoietic porphyria by high-performance liquid chromatography

A reversed-phase high-performance liquid chromatographic method is described for the determination of hydroxy and peroxy acid derivatives of uroporphyrin in the plasma of patients with congenital erythropoietic porphyria. The porphyrins were extracted from the plasma with 20% trichloroacetic acid-dimethyl sulphoxide (1:1, v/v). The supernatant after centrifugation was chromatographed on a Hypersil-ODS column by gradient elution with 9% (v/v) acetonitrile in 1 M ammonium acetate buffer (pH 5.16) (solvent A) and 10% (v/v) acetonitrile in methanol (solvent B) as the gradient mixture. The method was also suitable for the preparative isolation of the porphyrins.

Identification of peroxyacetic acid uroporphyrin I in the urine of patients with congenital erythropoietic porphyria by liquid chromatography and mass spectrometry

A new porphyrin, peroxyacetic acid uroporphyrin I, has been isolated from the urine of patients with congenital erythropoietic porphyria by reversed phase high performance liquid chromatography. The porphyrin was characterized by high resolution mass spectrometry and by typical chemical reactions of a peroxyacid.