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PubMed1978

[Comparative study of five different methods for measuring urinary porphyrins (author's transl)].

The AA. have compared five different methods for measuring urinary porphyrins (Bio-Rad porphyrins, Porphyrin-T Sibar, Reinkingh-Van Kampen, Schwartz and coll., Fischer-Ham). Based on the results obtained, for total porphyrins the best method appeared to be the Porphyrin-T Sibar test, while for the separate evaluation of uro- and coproporphyrins the most suitable method proved to be the one proposed by Reinkingh-Van Kampen. The investigations has also allowed the AA. to conclude that spectrophotometric reading can replace the fluorimetric one, without affecting the accuracy of results.

Coproporphyrins↗
PubMed1995

[Urinary porphyrin screening tests].

While it is known that urinary porphyrins are invariably increased in all varieties of porphyrias, no analytical device, color-developing solution or test paper for specific use in quantifying porphyrins is as yet available. Determination of porphyrins, requiring highly specialized technical skill and experience, is now being done, only in a limited number of special laboratories. For this reason, porphyrias in so many instances are detected late in the course of disease and few physicians are aware of the necessity for making porphyrin measurement. Of greatest importance in the diagnosis of porphyrias is the urinary screening test for porphyrins and screening tests reported to date, though not in widespread use, include those that make use of spectrum, argon ion laser, thin-layer chromatography and ion exchange column chromatography. In this paper, an account is given of three methods currently in most extensive use, i.e. the Schwartz method, Brugsh-Fischer method and high-performance liquid chromatography method, and microplate fluorescence technique, recently developed by the author.

Chromatography, High Pressure Liquid↗
PubMed1993

Influence of clonidine on the porphyrin metabolism in female rats.

Effects of different doses of clonidine (CAS 4205-90-7) (15, 150, or 300 micrograms/kg body weight) over a period of 3, 14, or 64 days on the activities of delta-aminolevulinic acid synthase (ALA-S) and the P450 dependent isoenzymes aminopyrine-N-demethylase (ADM), 7-ethoxycoumarin-O-deethylase (7-ECO-D), and 7-ethoxyresorufin-O-deethylase (7-ERO-D) as well as on the hepatic porphyrin and P450 content were studied in female rats. Additionally, the urinary excretion of total porphyrins, and porphyrin precursors delta-aminolevulinic acid (ALA) and porphobilinogen (PBG) and the plasma clonidine level were measured. No changes in the activity of ALA-S and in the hepatic and urinary porphyrin, ALA and PBG contents were observed. An increase in the activities of ADM in the short and median term application of clonidine and of 7-ERO-D in the long term application was detected. It is concluded from these findings that clonidine has no effect on the porphyrin biosynthesis, but has an influence on the activities of P450 dependent isoenzymes ADM or 7-ERO-D.

5-Aminolevulinate Synthetase↗
PubMed1994

[Porphyrin metabolism in chronic liver diseases].

Out of 147 patients with chronic hepatic diseases, chronic persistent hepatitis, chronic active hepatitis, hepatic cirrhosis, alcoholic lesions of the liver, biliary hepatic cirrhosis and Gilbert syndrome were registered in 26, 35, 27, 43, 8 and 8 patients, respectively. Urinary and fecal porphyrins were measured spectrophotometrically. Disturbances in porphyrin metabolism were diagnosed in 76 patients (51.7%). Four different biochemical syndromes were identified: 1) a symptomatic rise of fecal porphyrins only, 2) secondary coproporphyrinuria, 3) secondary coproporphyrinuria in combination with high fecal protoporphyrin, 4) biochemical syndrome of chronic latent hepatic porphyria. These syndromes were not strictly specific, but secondary coproporphyrinuria occurred significantly more often in chronic active hepatitis and biliary cirrhosis. High symptomatic fecal porphyrins were characteristic for alcoholic affections, and latent hepatic porphyria was indicative of hepatic cirrhosis. Disturbed porphyrin metabolism arises in more severe hepatic lesions and runs in association with more rapid development of hepatocellular insufficiency. Probable pathochemical mechanism and diagnostic value of the above impairment are discussed.

Adolescent↗
PubMed1977

Clinical aspects of porphyrin measurement, other than lead poisoning.

Measurement of porphyrins and porphyrin precursors has clinical significance beyond the detection or confirmation of lead poisoning. The porphyric diseases of man are characterized by the presence of a specific clinical syndrome and demonstration of abnormal porphyrin excretion or accumulation in the tissues. In addition, porphyrins accumulate in other disorders that are unrelated to lead poisoning or the porphyrias. These causes of erythrocyte porphyrin accumulation, porphyrinuria, and the porphyrias are discussed.

Anemia↗
PubMed1995

Complex formation of heterocyclic amines with porphyrins: its use in detection and prevention.

Porphyrins can suppress mutagenicity of heterocyclic amines. We have shown using the Ames Salmonella test that the mutagenicity of heterocyclic amines is efficiently inhibited by addition of hemin, the red blood porphyrin, in the assay mixture. In this suppression, hemin acts in two ways; inhibition of metabolic activation and suppression of the mutagenicity in the metabolically activated heterocyclic amines. In both of these actions, a complex formation between the porphyrin molecule and the planar molecules of heterocyclic amines seems to play a role. Complex formation and its use in detecting heterocyclic amines in various samples can be seen in the case for copper phthalocyanine, a blue pigment with a porphyrin-like structure. Cellulose bearing copper phthalocyanine trisulfonate as ligand was found to be a selective adsorbent for polycyclic compounds. This adsorbent, named blue cotton/blue rayon, adsorbs polycyclics in aqueous media by forming complexes on the ligand molecules, and releases the adsorbed compounds in organic solvents, such as in methanol plus a small amount of ammonia. The ease in manipulation and its high efficiency have made the blue cotton/blue rayon technique a means now widely used in detecting heterocyclic amines and other polycyclic mutagens in crude samples such as food, urine, and even river water. Chlorophyll, a green plant porphyrin, is another example. Chlorophyll and its stable form, chlorophyllin, have been shown to be inhibitory against the mutagenicity of heterocyclic amines. We have prepared Sepharose-supported chlorophyllin and have shown that heterocyclic amines are adsorbable to this ligand in a reversible fashion. Complex formation between chlorophyllin and heterocyclic amines is also suggested from spectrophotometric studies. A preliminary in vivo study has shown that chlorophyllin is effective in diminishing the cooked beef-derived urinary mutagenicity in humans.

Amines↗
PubMed1996

Dependence of growth, metabolic expression, and pathogenicity of Naegleria fowleri on exogenous porphyrins.

The pathogenicity of the free-living amoeba Naegleria fowleri is modulated by the composition of the medium used for cultivation. The constituents that determine the level of pathogenicity of N. fowleri, however, have not been definitively established. The present study examined the effects of selected porphyrins on N. fowleri amoebae. The iron-containing porphyrins, hemin or hematin, or the iron-free porphyrin, protoporphyrin IX, were effective in supporting growth of N. fowleri in Cline medium lacking serum. Iron-binding proteins, including hemoglobin, could not satisfy the growth requirement of the amoebae for exogenous porphyrin. Expression of biological functions including azocaseinase activity, agglutination, mobility, complement susceptibility, and virulence were altered by the composition of the growth medium. Amoebae grown in Cline medium supplemented with either hemin or protoporphyrin IX displayed greater mobility and were more resistant to lysis by complement than those grown in Nelson medium. Similarly, amoebae grown in Cline medium supplemented with either hemin or protoporphyrin IX were more pathogenic for B6C3F1 mice than those grown in Nelson medium. The addition of protoporphyrin IX to Nelson medium resulted in a modest increase in mobility, resistance to complement lysis and virulence when compared to N. fowleri amoebae grown in Nelson medium without added porphyrin.

Agglutination↗
PubMed1998

Supramolecular cationic tetraruthenated porphyrin and light-induced decomposition of 2'-deoxyguanosine predominantly via a singlet oxygen-mediated mechanism.

The tetraruthenated porphyrin, mu-[meso-5,10,15,20-tetra(pyridyl)porphyrin]tetrakis[bis-(bipyridine) chloride ruthenium(II)] (TRP) is a supramolecular cationic species. The aim of the present investigation was to evaluate the photodynamic properties of TRP and Zn-TRP to damage DNA with emphasis on the mechanistic aspects. The ability for tetraruthenated porphyrin derivatives to induce photosensitization reactions has been determined using 2'-deoxyguanosine as a DNA model compound. The main photooxidation products of the targeted nucleoside were identified and classified according to their mechanisms of formation, involving either a radical pathway (type I) or a singlet oxygen-mediated mechanism (type II). Quantification of the different oxidation products provides a means to evaluate the relative contribution of type I and type II pathways associated with the oxidative photosensitization of 2'-deoxyguanosine by tetraruthenated porphyrin derivatives. Results indicate that 1O2 plays a major role in the mechanism of photooxidation mediated by these porphyrin derivatives. In addition an increase of the photosensitizing effect in the presence of zinc is observed. For each sensitizer, the ratio between type II and type I photoproducts has been calculated and compared to that of other known dyes such as methylene blue and riboflavin.

DNA Damage↗
PubMed1999

Effects of cationic porphyrins as G-quadruplex interactive agents in human tumor cells.

A series of cationic porphyrins has been identified as G-quadruplex interactive agents (QIAs) that stabilize telomeric G-quadruplex DNA and thereby inhibit human telomerase; 50% inhibition of telomerase activity was achieved in HeLa cell-free extract at porphyrin concentrations in the range < or = 50 microM. Cytotoxicity of the porphyrins in vitro was assessed in normal human cells (fibroblast and breast) and human tumor cells representing models selected for high telomerase activity and short telomeres (breast carcinoma, prostate, and lymphoma). In general, the cytotoxicity (EC50, effective concentration for 50% inhibition of cell proliferation) against normal and tumor cells was > 50 microM. The porphyrins were readily absorbed into tumor cell nuclei in culture. Inhibition of telomerase activity in MCF7 cells by subcytotoxic concentrations of TMPyP4 showed time and concentration dependence at 1-100 microM TMPyP4 over 15 days in culture (10 population doubling times). The inhibition of telomerase activity was paralleled by a cell growth arrest in G2-M. These results suggest that relevant biological effects of porphyrins can be achieved at concentrations that do not have general cytotoxic effects on cells. Moreover, the data support the concept that a rational, structure-based approach is possible to design novel telomere-interactive agents with application to a selective and specific anticancer therapy.

Antineoplastic Agents↗
PubMed2001

Enhanced intersystem crossing in donor/acceptor systems based on zinc/iron or free-base/iron porphyrins.

The deactivation pathways of the singlet excited state of a series of zinc or free-base donor porphyrins covalently linked by a bridge to a paramagnetic iron(III) chloride porphyrin acceptor have been studied. These donor-bridge-acceptor systems all share a similar geometry (25 A donor-acceptor center-to-center distance), but the bridges vary in electronic structure. In previously reported investigations of zinc/iron porphyrin systems, the fluorescence quenching of the donor has predominantly been assigned to electron transfer. However, for the porphyrin systems studied in this paper, we show that the dominant deactivation channels are enhanced intersystem crossing and singlet energy transfer. In both series, the intersystem crossing rate (S1-->T1) of the donor moiety is almost doubled in the presence of a paramagnetic high-spin metal-porphyrin acceptor. The significant spectral overlap of the donor fluorescence and acceptor absorption in both series allows for efficient singlet energy transfer (Forster mechanism). Furthermore, the bridging chromophores mediate energy transfer and the enhancement is inversely dependent upon the energy gap between the donor and bridge excited states. Although Marcus theory predicts thermodynamically favorable electron transfer to occur in the systems investigated, the quenching rate constants were found to be independent of solvent polarity, and no charge-separated state could be detected, indicating very small electronic coupling for electron transfer.

Journal Article↗
PubMed2001

Interaction between dioxoruthenium(VI) porphyrins and hydroxylamines: coordination of N-substituted hydroxylamine to ruthenium and X-ray crystal structures of ruthenium complexes with a unidentate nitrosoarene ligand.

The interactions between dioxoruthenium(VI) porphyrins 1 with N-phenylhydroxylamine or unsubstituted hydroxylamine are described. Reaction of complexes 1 with excess PhNHOH leads to isolation of bis(nitrosobenzene)ruthenium(II) porphyrins 3 and mono(nitrosobenzene)ruthenium(II) porphyrins 4. Both the types of ruthenium complexes are characterized by 1H NMR, IR, and UV/Vis spectroscopy, and mass spectrometry. The X-ray structure determinations on [Ru(II)(TPP)(PhNO)2] (3a), [Ru(II)(2,6-Cl-TPP)(PhNO)2] (3e), and [Ru(II)(4-MeO-TPP)(PhNO)(PhNH2)] (4d) (TPP tetraarylporphyrin) disclose a unidentate nitrosoarene coordination in all these complexes, with Ru-N(PhNO) bond lengths of 2.003(3) (3a, average), 1.991(3) (3e, average), and 2.042(2) A (4d). In the case of 4d, the Ru-N(PhNH2) bond length is found to be 2.075(3) A. Mechanistic investigations reveal the formation of intermediates [Ru(II)(Por)(PhNO)(PhNHOH)] (5; Por=porphyrin), a ruthenium complex with N-substituted hydroxylamine ligand, in the "1 + PhNHOH" system. The Ru-NH(OH)Ph moiety in 5 undergoes no rapid exchange with free PhNHOH in solution at room temperature, as revealed by 1H NMR spectroscopy. Unlike the interaction between complexes 1 and PhNHOH, reaction of such complexes with NH2OH affords nitrosylruthenium(II) porphyrins [Ru(II)(Por)(NO)(OH)] (6).

Catalysis↗
PubMed2003

Synthetic expanded porphyrin chemistry.

Expanded porphyrins are synthetic analogues of the porphyrins, and differ from these and other naturally occurring tetrapyrrolic macrocycles by containing a larger central core with a minimum of 17 atoms, while retaining the extended conjugation features that are a hallmark of these quintessential biological pigments. The result of core expansion is to produce systems with novel spectral and electronic features, interesting and, often unprecedented, cation-coordination properties, and, in many cases, an ability to bind anions in certain protonation states. Also adding to the appeal of expanded porphyrins is their central role in addressing issues of aromaticity. In many cases, they also display structural features, such as decidedly nonplanar "figure-eight" motifs, that have no antecedents in the chemistry of porphyrins or related macrocyclic compounds. In this Review, the various synthetic approaches now being employed to produce expanded porphyrins as well as their various applications-related aspects are discussed.

Journal Article↗
PubMed2003

A functionalized noncovalent macrocyclic multiporphyrin assembly from a dizinc(II) bis-porphyrin receptor and a free-base dipyridylporphyrin.

The bis-porphyrin system ZnP(2), in which two zinc porphyrins are connected by a phenanthroline linker in an oblique fashion, acts as a bifunctional receptor towards the complexation of free-base meso-5,10-bis(4'-pyridyl)-15,20-diphenylporphyrin (4'-cis DPyP). In solution, NMR spectroscopy evidenced quantitative formation of the tris-porphyrin macrocyclic assembly ZnP(2)(4'-cis DPyP), in which the two fragments are held together by two axial 4'-N(pyridyl)-Zn interactions. The remarkable stability of the edifice (an association constant of about 6x10(8) M(-1) was determined by UV/Vis absorption and emission titration experiments in toluene) is due to the almost perfect geometrical match between the two interacting units. The macrocycle was crystallized and studied by X-ray diffraction, which confirmed the excellent complementarity of the two components. Photoinduced energy transfer from the singlet excited state of the zinc porphyrin chromophores to the free-base porphyrin occurs with an efficiency of 98 % (k(en)=2x10(10) s(-1) in toluene, ambient temperature) with a mechanism consistent with a dipole-dipole process with a low orientation factor.

Crystallography, X-Ray↗
PubMed2005

Energy and electron transfer in polyacetylene-linked zinc-porphyrin-[60]fullerene molecular wires.

The synthesis and electrochemical and photophysical studies of a series of alkyne-linked zinc-porphyrin-[60]fullerene dyads are described. These dyads represent a new class of fully conjugated donor-acceptor systems. An alkynyl-fullerene synthon was synthesized by a nucleophilic addition reaction, and was then oxidatively coupled with a series of alkynyl tetra-aryl zinc-porphyrins with 1-3 alkyne units. Cyclic and differential pulse voltammetry studies confirmed that the porphyrin and fullerene are electronically coupled and that the degree of electronic interaction decreases with increasing length of the alkyne bridge. In toluene, energy transfer from the excited zinc-porphyrin singlet to the fullerene moiety occurs, affording fullerene triplet quantum yields of greater than 90 %. These dyads exhibit very rapid photoinduced electron transfer in tetrahydrofuran (THF) and benzonitrile (PhCN), which is consistent with normal Marcus behavior. Slower rates for charge recombination in THF versus PhCN clearly indicate that charge-recombination events are occurring in the Marcus inverted region. Exceptionally small attenuation factors (beta) of 0.06+/-0.005 A(-1) demonstrate that the triple bond is an effective mediator of electronic interaction in zinc-porphyrin-alkyne-fullerene molecular wires.

Acetylene↗
PubMed1991

Porphyrins as contrast media.

The interest in tissue distribution of variously labeled or otherwise detectable natural and synthetic porphyrins and porphyrin derivatives dates back well over 60 years. Although a considerable interest in fluorescent tumor localization and therapy dominates the history of porphyrin biodistribution studies, many investigators have evaluated the diagnostic and therapeutic characteristics of porphyrins with radioactive, radiopaque, and paramagnetic qualities. In this paper, a review of the use of porphyrins as nuclear medicine, X-ray, and NMR contrast agents is presented.

Animals↗
PubMed1999

Manganese and iron porphyrins catalyze peroxynitrite decomposition and simultaneously increase nitration and oxidant yield: implications for their use as peroxynitrite scavengers in vivo.

Twelve substituted metalloporphyrins (MPs), some of which have been previously characterized with respect to superoxide dismutase and peroxynitrite decomposing activities, were evaluated for their ability to scavenge peroxynitrite in vitro at 37 degrees C. Because the overall effectiveness of MPs as catalytic peroxynitrite scavengers is a function of (1) how fast they react with peroxynitrite, (2) how fast they cycle back to the starting compound, and (3) how well they contain or quench the reactive intermediates generated, all of these properties were evaluated and compared directly under the same conditions. Of the various MPs tested, only the iron and manganese porphyrins showed significant reactivity with peroxynitrite. The Mn(IV) intermediates resulting from oxidation by peroxynitrite were relatively stable and rereduction to the Mn(III) forms was rate-limiting to catalytic decomposition of peroxynitrite. However, in the presence of oxidizeable substrates like phenolics, rereduction of Mn(IV) forms occurred very rapidly and both the Mn- and Fe-porphyrins catalyzed nitration and oxidation by peroxynitrite. Mn- and Fe-porphyrins enhanced the yield of nitrated phenolics by peroxynitrite as much as 5-fold at pH 7.4 and up to 12-fold at pH 9. 1, while total oxidative yield was more than doubled. Nitration enhancement by MPs was effectively inhibited by ascorbate, glutathione, or serum, although much higher concentrations of ascorbate were required to inhibit nitration catalyzed by either Mn or Fe tetramethylpyridyl porphyrin. Catalysis of peroxynitrite nitration by MPs appears to proceed via a radical-mediated reaction mechanism whereby the phenolic substrate rapidly reduces Mn(IV) = O or Fe[IV] = O to the +3 state to yield phenoxyl radical which then combines with the other primary product, nitrogen dioxide. Based on the rate constants and the proposed reaction mechanism, it is reasonable to suggest that Mn and Fe porphyrins could detoxify peroxynitrite in vivo by efficiently trapping the relatively unreactive peroxynitrite anion and, in effect, channeling it into a single reaction pathway which could then be more effectively scavenged by cellular reductants like ascorbate.

Ascorbic Acid↗
PubMed2002

Electrochemical metallization of self-assembled porphyrin monolayers.

Multifunctional sensor systems are becoming increasingly important in electroanalytical chemistry. Together with ongoing miniaturization there is a need for micro- and nanopatterning tools for thin electroactive layers (e.g. self-assembling monolayers). This paper documents a method for production of a micro-array of different metal-porphyrin monolayers with different sensor properties. A new method has been developed for the selective and local metallization of bare porphyrin monolayers by cathodic pulsing and sweeping. The metal-porphyrin monolayers obtained were characterized by cyclic voltammetry. It was shown that porphyrin monolayers can be metallized with manganese, iron, cobalt, and nickel by use of the new method. It is expected that all types of metal-porphyrin monolayers can be produced in the same manner.

Journal Article↗
PubMed1990

The enzymatic one-electron reduction of porphyrins to their anion free radicals.

The anaerobic enzymatic one-electron reduction of uroporphyrin I (in the absence of light) by the ferredoxin/ferredoxin:NADP+ oxidoreductase system was investigated using NADPH as the source of reducing equivalents. The porphyrin anion free radical metabolite formed by one-electron reduction of the parent molecule was detected with ESR spectroscopy. The ESR spectrum exhibited a singlet (g = 2.0021) with a 5.4-G peak-to-peak linewidth. The reduction process was also investigated under aerobic conditions. The reduction of molecular oxygen to superoxide anion radical by the porphyrin anion radical was demonstrated by using the ESR technique of spin trapping. The ESR spectra of the spin-trapped oxygen-derived radicals were superoxide dismutase-sensitive and catalase-insensitive, supporting the assignment of the trapped radical to the superoxide anion radical. These aerobic experiments demonstrate electron transfer from the porphyrin anion radical to molecular oxygen. The anaerobic reduction of Photofrin II by hepatic microsomes and the ferredoxin/ferredoxin:NADP+ oxidoreductase system to a porphyrin anion radical was also investigated. Free radical formation by ferredoxin: NADP+ oxidoreductase is totally dependent upon ferredoxin. The ESR spectrum of this porphyrin free radical also exhibited a singlet (g = 2.0026) with a 15-G peak-to-peak linewidth.

Animals↗