Porphyrin-degraded product

Fio. 3. Nonporphyrinic metals (a) vanadyl hydroporphyrin, (b) vanadyl arylporphyrin (highly aromatic porphyrin), (c) porphyrin-degraded product (bilirubin). (Yen, 1975). 

Porphyrin-degraded products such as open-chain bile pigments were also detected. The stability of vanadyl m-tetra-a-naphyl porphin and other high aromatic derivatives is unusually high. ... 

Porphyrins organometallic constituents of petroleum that contain vanadium or nickel the degradation products of chlorophyll that became included in the protopetroleum. 

Table 1 provides a fairly comprehensive listing of trivial names still in regular use in the porphyrin and chlorophyll area. The uro-, copro- and etio-porphyrins are examples of primary type isomer systems, while proto-, meso-, deutero- and hemato-porphyrins derive from the situation where 15 isomers exist. Phyllo-, pyrro- and rhodo-porphyrins, all being chlorophyll degradation products, are examples of the situation where there are four different kinds of porphyrin substituent. It transpires that, in biologically important porphyrin derivatives, the isomer chosen by Nature is Type-Ill (for the primary system), Type-IX (with three types of substituent) and Type-XV (with four). As can be seen in Schemes 1 and 2, primary type-III is related to type-IX in Scheme 2, and type-IX is in turn related to type-XV in the yet more complicated four-substituent system. 

The nature of the petroporphyrins found in a variety of crude oils, oil shales, ancient and recent sediments have been a subject of continual interest since these compounds were first isolated from such materials by Treibs (l) some fifty years ago. It is now generally agreed ( 2) that the petroporphyrins represent the degradation products of chlorophyll and that they consist predominantly of homologous series of deoxophyllo-erythroetioporphyrin (DPEP) and aetio porphyrins. However, as yet unidentified porphyrin compounds which do not belong to either of these two classes have been observed (JO in some samples and the proposition that all petroporphyrins are derived from chlorophyll has also been questioned (4). 

Liquid-phase catalysts are close models to enzymes and can be a gentle alternative method of destruction of halogenated hydrocarbons. Transition metal complexes, in particular metal porphyrins, corrins and phthalocyanines, have been studied in homogeneous abiotic aqueous systems as potential remediation catalysts, but further identification of degradative products is necessary, since innocuous products must result if synthetic catalysts are to be used effectively. Moreover, the implementation of homogeneous catalysts is still impractical because of problems with separating the catalyst in principle these can be overcome by immobi-... 

In the present definition, the nonporphyrins will also include the altered or modified porphin structure, such as hydroporphins (ab), arylporphins (ac), and porphin-degraded products (ad). All three classes have been included in the discussion of the above section since they are the secondary or tertiary derivatives or the precursors of the regular porphin structure (aa). In many cases they lose their porphyrin identity (properties) even when they exist in the same environment. 

Several other nitrogen-containing metabolites, notably the bile pigments, are also excreted. These are degradation products of hemoglobin and various porphyrin-containing molecules. 

The major nitrogen-containing metabolites are urea (-84% of total nitrogen), uric acid (-2%), creatinine (-5%), ammonia (-5%), amino acids (-4%), protein (trace), and degradation products of porphyrins (trace, a few tens of mg). The amounts of these substances can vary. E.g., the amount of urea will increase during starvation and when a person is eating a high-protein diet and creatinine excretion will increase after physical activity. 

Figure 8 Mechanistic pathways for the one-electron initiated degradation of a lignin model. Note that any oxygen incorporated into degradation products arises from H2O or O2 and not from any 0=Fe porphyrin species... 

The structural type of C. (2,3-dihydroporphyrins) is formally derived from that of porphyrin by reduction of a peripheral double bond in a pyrrole ring of the porphyrin skeleton. The name is based on that of chlorophyll which possesses the C. skeleton with a central magnesium(ll) ion. Other substances with the C. skeleton are, in addition to the chlorophylls and their degradation products, some bacterioch)orophylls, bo-nellin, chlorophyllone, cyclopheophorbide, factor I, heme d, and tunichlorin. 

C33H46N4O6, Mr 594.75, mp. 238 °C, (a]g -4000° (hydrochloride), [a] -870° (free base), golden yellow oxidation product of stercobilinogen, considered to be the final product of porphyrin degradation in warmblooded organisms. S. is present in urine and feces and is in part responsible for the color of feces. 

Stercobillnogen. Formula, see stercobilin (saturated at C-10- and N-23). C33H4,N40, Mr 596.77. S. is formed in the intestines by bacterial degradation of the bile pigment bilirubin via urobilinogen and thus represents the actual final product of porphyrin degradation in warm-blooded organisms. It is excreted in urine and feces where it is easily oxidized to stercobilin. 

In the MOF PIZA-3 (PIZA, porphyrinic Illinois zeolite analog), Mn(III) is found both in the porphyrin struts and as a structural metal node. The framework is structurally stable and is used for the oxidation of cycUc alkanes and alkenes with iodosylbenzene or peracetic acid as the oxidant [117]. Reaction is found to take place at the outer surface, which is justified by the authors by the unfavorable hydrophilic properties of the pore interior. Yields were similar to those obtained with homogeneous Mn(III) porphyrin systems or those immobilized inside inorganic supports as heterogeneous catalysts. Less than 0.1 mM of metalloporphyrin or degradation products were observed in the reaction mixtures, with no loss of oxidation activity observed in a second run when peracetic acid was used. 

As reported in his Nobel lecture and in a variety of subsequent publications by others, the large number of reactions that had been undertaken to synthesize various pyrroles and the techniques of linking them to form porphyrins led to a clear understanding of the structures of heme and chlorophyll and their various degradation products. 

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