Porphyrin Research Articles

Effect of linoleic acid-induced oxidation on the water retention of golden pompano: Myoglobin and myofibrillar protein oxidation

This study investigated the interrelationship among changes in myoglobin (Mb) morphology, myofibrillar protein (MP) oxidation, and water-holding capacity (WHC) of golden pompano under oxidized linoleic acid (OLA). Results showed that the WHC, springiness, and chewiness of golden pompano were increased at low OLA concentrations. Compared with the control, centrifugal and cooking losses were reduced by 11.78% and 6.22%, respectively. By contrast, high concentrations of OLA showed a decreasing trend in muscle WHC. The porphyrin ring of Mb was disrupted, and the contents of heme and heme iron were significantly decreased (P < 0.05) during oxidation. The carbonyl content gradually increased, whereas total sulfhydryl decreased with the increase in OLA concentration. The α-helix contents of MP decreased and the random coil increased. The surface hydrophobicity of MP increased (≤10 mmol/L), and then gradually decreased with the increase of OLA concentrations. The Pearson analysis showed that WHC was closely related to protein oxidation. Mb would be pre-oxidized before MP due to linoleic acid oxidation, which may further promote oxidation and cause structural changes in MP, affecting WHC in golden pompano. Muscle WHC would be increased at low OLA concentrations (≤10 mmol/L), while reduced at high OLA concentrations (≥20 mmol/L).

Autofluorescence spectroscopy in photodynamic therapy for skin rejuvenation: A theranostic approach in aesthetic medicine

BackgroundThe method of photodynamic therapy for skin rejuvenation (PDT-SR) provides an improvement in appearance with a safe and painless effect. The quality of treatment is most often assessed subjectively. The most informative morphological control methods are rarely used due to the invasiveness of the sampling procedure. AimThis study aimed to find out the possibility of using skin autofluorescence spectroscopy (SAF) for an objective assessment of changes occurring in the skin during PDT-SR. MethodsThis study included 12 volunteers (10 women, 2 men) aged 32 to 79 years. Two (n = 6) or three (n = 6) PDT sessions were performed at intervals of 13–30 days. Photosensitizer chlorin e6, exposure 20 min, energy density 18–24 J/cm2 were used. SAF spectra were recorded using a two-wavelength fiber optic spectrometer under excitation at wavelengths (λex) of 365 nm and 440 nm. Measurements were made both before and after each PDT session and up to 25–238 days from the start of treatment. For the evaluation, we used the spectra AF365(λ) and AF440(λ) averaged over 40 points corrected for diffuse reflection at λex=440 nm in the range λem= 460–700 nm, as well as the spectra of the ratios AFN365(λ) and AFN440(λ), which were obtained by dividing the intensities of the current spectra by the intensities collected before PDT-SR. ResultsPDT-SR led to changes in both the intensity and shape of the spectra. Analysis of the spectra using numerical fitting of the spectra showed that the main changes can be explained by changes in the content of advanced glycation end products (AGEs), as well as lipofuscin-like lipopigments (LPs) and porphyrins (PPs). The spectra of AGEs upon excitation at wavelengths of 365 and 440 nm differ, which may be due to the formation of two types of bonds, with collagen and elastin. By the end of the study, the vast majority of the examined volunteers showed a significant decrease of the parameters characterizing both of these types of AGEs, AGE365 (0.56–1.2) and AGE440 (0.58–1.01), relative to the beginning of the study. In most cases, a decrease was also noted for LPs and PPs. AGE365 and AGE440 were positively correlated with the age of the volunteers (r2 = 0.26–0.46 %). A steady decrease in the content of AGEs occurred approximately on the 40th day. ConclusionSAF spectroscopy makes it possible to assess changes in the content of AGEs, LPs, and PPs in the skin during PDT-SR. The method has great potential for non-invasive monitoring of the treatment process, as well as its improvement, including through its personalization. In addition, the method can be used to study the mechanisms of age-related skin changes at the molecular level and to study the processes of rejuvenation.

Dispersed Bi2S3 site in a porphyrin-based metal–organic framework for photocatalytic nitrogen fixation

The development of suitable alternatives to the energy-intensive and seriously polluting Haber–Bosch process for ammonia production is crucial. Photocatalytic nitrogen fixation has attracted extensive research attention as a pollution-free, low-cost, and sustainable ammonia production process. However, most reported photocatalysts so far have relatively low conversion rates for N2 reduction. Herein, we employed a strategy based on bismuth precoordination and in-situ sulfurization strategy to grow highly dispersed bismuth sulfide (Bi2S3) on a porous coordination network (PCN) metal–organic framework. The as-fabricated photocatalyst (Bi2S3@PCN-2) with high-density heterojunctions was used for the photocatalytic nitrogen fixation for ammonia production and degradation of bisphenol A, achieving an ammonia production rate of 3880 μg h−1 g−1 and a 96.4% degradation efficiency for bisphenol A within 30 min in the absence of a sacrificial agent. The abundant porphyrin rings and highly dispersed Bi2S3 broadened the visible-light absorption range of the photocatalyst, leading to numerous photogenerated charge carriers. Additionally, the high-density heterojunctions facilitated the separation of photogenerated electron–hole pairs, resulting in excellent photocatalytic performance. This work provides a new approach for the design and preparation of bifunctional photocatalysts.

Porphyrin Helical Nanochannel‐Assembled Polybenzimidazole Membranes Doped with Phosphoric Acid for Fuel Cells Operating in a Temperature Range of 25–200 °C

AbstractHigh‐temperature proton‐exchange membrane fuel cells (HT‐PEMFCs) fabricated with phosphoric acid (PA)‐doped polybenzimidazole (PBI) show apparent technical advantages. In practical automotive applications, achieving cold start‐up capability is crucial. In this work, a kind of branched block proton exchange membrane (PEM) based on PBI with a low content of porphyrin ring (&lt;1 mol.%) is reported as a branched monomer. Self‐assembly into high‐density helical nanochannels under the synergistic effect of phase separation and porphyrin π−π stacking, thus the PEM can maintain a high level of PA doping. Specifically, the PA/1.8TCPP‐BrPy‐OPBI membrane shows a proton conductivity of 0.169 and 0.071 S cm−1, as well as an H2‐O2 fuel cell peak power density of 1077 and 357 mW cm−2 at 180 and 80 °C without humidification and backpressure, respectively. The membrane electrode assembly (MEA) can exhibit good fuel cell stability, with a voltage decay rate of only 7.0 µV h−1 at 80 °C. Furthermore, it maintains a peak power density of 93% even after 150 start‐up/shut‐down cycles at 25 °C. This work expands the operating temperature range of conventional PBI membranes between 25 and 200 °C and thus provides a novel strategy for high‐performance PBI‐based HT‐PEMFCs.

Achieving selective CO2 capture and separation in crosslinked porous porphyrin-based polyimide skeletons

The precise control of porous structure has always been a key factor for porous materials. We tuned the porous structures by enhancing alkynyl-groups contents and introducing metal into porphyrin ring. We used simple polymerization and alkynyl crosslinking reactions to construct crosslinked porous porphyrin-based polyimides (CR-PPBPIs) from 2,5-bis(3,4-dicarboxyphenoxy)-4’-phenylethynyl-biphenyl dianhydride (PEPHQDA) and 5,10,15,20-tetra[4-[(3-aminophenyl)ethynyl]phenyl] porphyrin (TAPEPP). CR-PPBPIs revealed BET surface areas (212, 578 and 593 m2 g−1), dominated pore width (1 and 1.9 nm) and abundant CO2-philic substances. Thus, considerable CO2 uptakes (1.92, 2.43 and 2.52 mmol g−1), CO2-adsorption isosteric enthalpies (31.9, 26.0 and 27.9 kJ mol−1) and superior CO2/N2 selectivities (45.77, 38.72 and 46.26) were achieved. This work sheds some light on the precise regulation of porosity parameters in the crosslinked metalloporphyrin-based polyimides for carbon dioxide adsorption and separation.

Bimetallic synergy significantly enhances the photocatalytic performance of lanthanide porphyrin-based MOFs: Efficient photocatalytic oxidation of benzyl alcohol and benzylamine under mild conditions in air

Metal-organic frameworks as photocatalysts for the conversion of light energy into chemical energy applied to organic conversion is an efficient and sustainable strategy. Lanthanide organometallic frameworks perform poorly in photocatalytic organic reactions owing to their high electron and hole complexation rates. Inspired by the synergistic effect of biomacromolecule porphyrin as a photosensitizer with bimetallic pairs that can boost electron transport efficiency. We synthesized a series of lanthanide porphyrin mechanism MOFs (Nd PMOFs, Co–Nd PMOFs, Ni–Nd PMOFs). These PMOFs are endowed with a novel three-dimensional structure. It is noteworthy that Ni in the middle of the porphyrin ring enhances the photocatalytic performance of Ni–Nd PMOFs. The reasons can be attributed to the introduced Ni and the coordinated Nd elements, which interact synergistically with the porphyrin skeleton. This interaction results in a good photoresponse and promotes an efficient separation of photogenerated electrons and holes. The photocatalytic performance of Ni–Nd PMOFs was tested under mild conditions (12 W visible light, air) using the photocatalytic oxidation of benzyl alcohol and the oxidative coupling of benzylamine as model reactions. The conversion rate for benzyl alcohol was 90 % with a selectivity 94 %, and the conversion rate for benzylamine was 85 % with a selectivity 83 %. The photocatalytic oxidation performance of Ni–Nd PMOFs has been found to be excellent for a wide range of reactions and substrates, indicating that it is a promising photocatalyst. To some extent, the presentation of this work expands the possibilities of lanthanide metal frameworks for photocatalytic organic transformations and sheds new light on the multidirectional applications of lanthanide metal–organic frameworks.

Fluoro-2,6-dimethylphenyl mono-hydroxychlorin and porphyrin congeners

Mono-hydroxychlorins are uncommon macrocycles that have only been synthetically realized by modifying porphyrin rings using the harsh oxidizing agent OsO4. We show here that a more directed delivery of the mono-hydroxychlorin may be concomitantly obtained from the oxidation of porphyrinogen using the mild conditions of the high dilution Lindsey porphyrin forming reaction where water content is minimized by using dry CHCl3 within the environment of a glovebox. We now report the direct synthesis of 17,18-dihydro-18-hydroxy-5,10,15,20-tetrakis-(4-fluoro,2,6-dimethylphenyl)-porphyrin (2H-TFChl-[Formula: see text]OH) together with the corresponding freebase porphyrin TFP. The TFP has been metalated with FeBr2 and MgBr2•OEt2 resulting in metalloporphyrins Fe(III)TFP(Cl) and Mg(II)-TFP which have been structurally characterized by single-crystal X-ray crystallography. We find that the excited state properties of the mono-hydroxychlorin are similar to that of its parent TFP and Mg(II)TFP porphyrin congeners. Excited state deactivation by vibronic coupling to the high energy O-H oscillator is circumvented with the hydroxyl group remote to the 18[Formula: see text]-electron framework of the chlorin ring. These results reveal that strong H-bonding groups may be introduced on the periphery of the chlorin ring while maintaining the light-gathering properties that lie at the heart of photosynthesis of the chlorin ring.

Functional study of Cygb in the immune response to Vibrio harveyi disease in yellow drum (Nibea albiflora)

Cytoglobin (Cygb) is a 21-kDa heme-protein that belongs to the globin superfamily and is expressed in vertebrate tissues. It can participate in the oxidative stress response in organisms through the porphyrin ring. Previous studies have shown that this protein, also known as YdCygb, has potential immune abilities in the infection of Vibrio harveyi in yellow drum (Nibea albiflora). In this study, we report the role of Cygb in the immune response of teleost fish for the first time. Quantitative RT-PCR analysis indicated that YdCygb was highly expressed in the liver and intestine of yellow drum, and its expression can be upregulated by pathogenic attack. The cellular distribution of YdCygb-EGFP proteins was observed in cell membrane, cytoplasm, and nucleus in the kidney cells of N. albiflora. Furthermore, a comparative transcriptome analysis between the YdCygb overexpression group and control vector group identified 28 differentially expressed genes (DEGs). The analysis showed that ANPEP, CLDN5, ORM1/2, SERPINC1 and HPN and ITGAM might play important regulatory roles to Cygb in fish. Notably, using GST-pull down technology, we identified 3-phosphoglyceraldehyde dehydrogenase and intermediate filament protein as direct interactors with YdCygb, playing a role against V. harveyi. The molecular and functional characterization of YdCygb provides better understanding of the genetic basis of disease resistance traits in yellow drum and sheds new light on the functioning of Cygb and its potential regulatory signaling pathway as well.

Investigation of J-Aggregates of 2,3,7,8,12,13,17,18-Octabromo-5,10,15,20-tetrakis(4-sulfonatophenyl) Porphyrin in Aqueous Solutions.

The highly distorted water-soluble 2,3,7,8,12,13,17,18-octabromo-5,10,15,20-tetrakis(4-sulfonatophenyl)porphyrin (Br8TPPS44-) is readily protonated under acidic pH, forming the diacid H2Br8TPPS42- and subsequently the zwitterionic H4Br8TPPS4, which eventually evolves into J-aggregates. These latter species exhibit a relevant bathochromic shift with respect to the monomer with a quite sharp band due to motional narrowing. The depolarization ratio measured in resonant light scattering spectra allows estimating a tilt angle of ~20° of the porphyrins in the J-aggregate. The kinetic parameters are obtained by applying a model based on the initial slow nucleation step, leading to a nucleus containing m monomers, followed by fast autocatalytic growth. The kc values for this latter step increase on decreasing the acid concentration and on increasing the porphyrin concentration, with a strong power-law dependence. No spontaneous symmetry breaking or transfer of chirality from chiral inducers is observed. Both Atomic Force Microscopy (AFM) and Dynamic Light Scattering (DLS) point to the presence, in both the solid and solution phases, of globular-shaped aggregates with sizes close to 130 nm. Density functional theory (DFT) calculations performed on simplified models show that (i) upon protonation, the saddled conformation of the porphyrin ring is slightly altered, and a further rotation of the aryl rings occurs, and (ii) the diacid species is more stable than the parent unprotonated porphyrin. Time-dependent DFT analysis allows comparing the UV/Vis spectra for the two species, showing a consistent red shift upon protonation, even if larger than the experimental one. The simulated Raman spectrum agrees with the experimental spectrum acquired on solid samples.

Tetraphenylporphyrin-based Chelating Ligand Additive as a Molecular Sieving Interfacial Barrier toward Durable Aqueous Zinc Metal Batteries.

The sustained water consumption and uncontrollable dendrite growth strongly hamper the practical applications of rechargeable zinc (Zn) metal batteries (ZMBs). Herein, for the first time, we demonstrate that trace amount of chelate ligand additive can serve as a "molecular sieve-like" interfacial barrier and achieve highly efficient Zn plating/stripping. As verified by theoretical modeling and experimental investigations, the benzenesulfonic acid groups on the additive molecular not only facilitates its water solubility and selective adsorption on the Zn anode, but also effectively accelerates the de-solvation kinetics of Zn2+ . Meanwhile, the central porphyrin ring on the chelate ligand effectively expels free water molecules from Zn2+ via chemical binding against hydrogen evolution, and reversibly releases the captured Zn2+ to endow a dendrite-free Zn deposition. By virtue of this non-consumable additive, high average Zn plating/stripping efficiency of 99.7 % over 2100 cycles together with extended lifespan and suppressed water decomposition in the Zn||MnO2 full battery were achieved, thus opening a new avenue for developing highly durable ZMBs.

Tetraphenylporphyrin‐based Chelating Ligand Additive as a Molecular Sieving Interfacial Barrier toward Durable Aqueous Zinc Metal Batteries

AbstractThe sustained water consumption and uncontrollable dendrite growth strongly hamper the practical applications of rechargeable zinc (Zn) metal batteries (ZMBs). Herein, for the first time, we demonstrate that trace amount of chelate ligand additive can serve as a “molecular sieve‐like” interfacial barrier and achieve highly efficient Zn plating/stripping. As verified by theoretical modeling and experimental investigations, the benzenesulfonic acid groups on the additive molecular not only facilitates its water solubility and selective adsorption on the Zn anode, but also effectively accelerates the de‐solvation kinetics of Zn2+. Meanwhile, the central porphyrin ring on the chelate ligand effectively expels free water molecules from Zn2+ via chemical binding against hydrogen evolution, and reversibly releases the captured Zn2+ to endow a dendrite‐free Zn deposition. By virtue of this non‐consumable additive, high average Zn plating/stripping efficiency of 99.7 % over 2100 cycles together with extended lifespan and suppressed water decomposition in the Zn||MnO2 full battery were achieved, thus opening a new avenue for developing highly durable ZMBs.

Entropy analysis of nickel(II) porphyrins network via curve fitting techniques

Nickel(II) porphyrins typically adopt a square planar coordination geometry, with the nickel atom located at the center of the porphyrin ring and the coordinating atoms arranged in a square plane. The additional atoms or groups coordinated to the nickel atom in nickel(II) porphyrins are called ligands. Porphyrins have been investigated as potential agents for imaging and treating cancer due to their ability to selectively bind to tumor cells and be used as sensors for a variety of analytes. Nickel(II) porphyrins are relatively stable compounds, with high thermal and chemical stability. They can be stored in a solid state or in solution without significant degradation. In this study, we compute several connectivity indices, such as general Randi’c, hyper Zagreb, and redefined Zagreb indices, based on the degrees of vertices of the chemical graph of nickel porphyrins. Then, we compute the entropy and heat of formation NiP production, among other physical parameters. Using MATLAB, we fit curves between various indices and the thermodynamic properties parameters, notably the heat of formation and entropy, using various linearity- and non-linearity-based approaches. The method’s effectiveness is evaluated using R^2, the sum of squared errors, and root mean square error. We also provide visual representations of these indexes. These mathematical frameworks might offer a mechanism to investigate the thermodynamical characteristics of NiP’s chemical structure under various circumstances, which will help us understand the connection between system dimensions and these metrics.

A Porphyrin Iron(III) π-Dication Species and its Relevance in Catalyst Design for the Umpolung of Nucleophiles.

Isoporphyrins have recently been identified as remarkable species capable of turning the nucleophile attached to the porphyrin ring into an electrophile, thereby providing umpolung of reactivity (Inorg. Chem. 2022, 61, 8105-8111). They are generated by nucleophilic attack on an iron(III) π-dication, a class of species that has received scant attention. Here, we explore the effect of the porphyrin meso-substituent and report a iron(III) π-dication bearing the meso-tetraphenylporphyrin (TPP) ligand. We provide an extensive study of the species by UV/Vis absorption, 2 H NMR, EPR, applied field Mössbauer, and resonance Raman spectroscopy. We further explore the system's highly dynamic and tunable properties and address the nature of the axial ligands as well as the conformation of the porphyrin ring. The insights presented are essential for the rational design of catalysts for the umpolung of nucleophiles. Such catalytic avenues could for example provide a novel method for electrophilic chlorinations. We further examine the importance of electronic tuning of the porphyrin by nature of the meso-substituent as a factor in catalyst design.

A Porphyrin Iron(III) π‐Dication Species and its Relevance in Catalyst Design for the Umpolung of Nucleophiles

AbstractIsoporphyrins have recently been identified as remarkable species capable of turning the nucleophile attached to the porphyrin ring into an electrophile, thereby providing umpolung of reactivity (Inorg. Chem. 2022, 61, 8105–8111). They are generated by nucleophilic attack on an iron(III) π‐dication, a class of species that has received scant attention. Here, we explore the effect of the porphyrin meso‐substituent and report a iron(III) π‐dication bearing the meso‐tetraphenylporphyrin (TPP) ligand. We provide an extensive study of the species by UV/Vis absorption, 2H NMR, EPR, applied field Mössbauer, and resonance Raman spectroscopy. We further explore the system's highly dynamic and tunable properties and address the nature of the axial ligands as well as the conformation of the porphyrin ring. The insights presented are essential for the rational design of catalysts for the umpolung of nucleophiles. Such catalytic avenues could for example provide a novel method for electrophilic chlorinations. We further examine the importance of electronic tuning of the porphyrin by nature of the meso‐substituent as a factor in catalyst design.

Effect of magnetic field modification on oxidative stability of myoglobin in sarcoplasm systems

This study aimed to investigate the effect of magnetic fields (0, 3, 6, 12 mT) on the oxidation characteristics of myoglobin (Mb) in the sarcoplasmic protein (SP) system and to understander the underlying mechanism. The metmyoglobin content, Soret band of heme iron porphyrin, protein conformation and molecular weight distribution were measured in different Mb and SP samples. The results showed that the primary oxidation site of hydroxyl radical on Mb was likely to be the porphyrin ring structure and the side chain group of protein rather than the central iron atoms, what’s more, 12 mT magnetic field treatment had an inhibitory effect on the oxidative damage induced by hydroxyl radical.

Synthesis, Structure, and Redox and Optical Properties of 5,10,15,20-Tetraaryl-5-azaporphyrinium Salts.

The fundamental properties of azaporphyrins can be modulated over a wide range by changing the number of meso-nitrogen atoms. We report herein the first examples of 5,10,15,20-tetraaryl-5-azaporphyrinium (MTAMAP) salts, which were prepared via metal-templated cyclization of the corresponding zinc(II) and copper(II) complexes of 10-aryl-1-chloro-19-benzoyl-5,15-dimesityl-10-azabiladiene-ac. The inclusion of one meso-nitrogen atom in the 5,10,15,20-tetraarylporphyrin skeleton considerably changes the redox and optical properties as well as the degree of aromaticity of the porphyrin ring. The present findings suggest that MTAMAP salts would be promising scaffolds for the development of new azaporphyrin-based ionic fluorophores and photosensitizers.

Synthesis and crystal structure of bis-(tert-butyl isocyanide-κC)[5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinato-κ4N]iron(II).

In the title compound, [FeII(C44H24Cl4N4)(C5H9N)2] or [FeII(TClPP)(t-BuNC)2] [where TClPP and t-BuNC are 5,10,15,20-tetra-kis-(4-chloro-phen-yl)porphyrinate and tert-butyl isocyanide ligands, respectively], the metal ion lies on an inversion center and is octa-hedrally coordinated by the N atoms of the porphyrin ring in the equatorial plane and by carbon atoms of the trans t-BuNC ligands in the axial sites. The Fe-N bond length of 2.0074 (14) Å suggests a low-spin complex (S = 0). The crystal packing of the title compound is sustained by C-H⋯Cl, C-H⋯N and C__H⋯Cg (Cg = the centroid of a pyrrole ring of the TClPP porphyrinate) inter-actions, leading to a three-dimensional network. The Hirshfeld surface (HS) analysis indicates that 61.4% of the inter-molecular inter-actions are from H⋯H contacts while other contributions are from C⋯H/H⋯C, O⋯H/H⋯O and N⋯H/H⋯N inter-actions, which comprise 21.3%, 13.3% and 3.6% of the HS, respectively.

Triazine- and porphyrin-based donor-acceptor microporous conjugated polymers for enhanced photocatalytic hydrogen production activity

Donor-acceptor type conjugated microporous polymers (D-A CMPs) have recently gained popularity as active components for photocatalytic hydrogen evolution from water due to their ability to separate the photoinduced holes and electrons efficiently and vastly absorb visible light. However, creating a novel CMP photocatalyst with high photoconversion efficiency is still difficult. Porphyrins and triazines exhibit intriguing electrical and optical features. We present here the directed synthesis and photocatalytic activity in hydrogen generation of two donor-acceptor isostructural triazine- and porphyrin-based conjugated microporous polymers (H-Por-TPT and Zn-Por-TPT CMPs). Our data demonstrate that both CMPs have extremely high specific surface areas (around 650 m2 g−1) and thermal stabilities (Td10: equal to 629 °C with char yields equal to 76.18 wt%). Introducing a Zn atom into a porphyrin ring profoundly influences its optoelectronic properties and photocatalytic efficiency for hydrogen generation from water. Zn-Por-TPT CMP has one of the highest reported values for a D-A CMP, with a photocatalytic hydrogen evolution rate of 11450 μmol g−1 h−1 when exposed to visible light. In addition, the Zn-Por-TPT CMP is notable not just for increasing the rate of hydrogen generation but also for improving photocatalysis stability during prolonged irradiation for roughly 30 h. These CMPs may prove useful as organic photocatalysts in future photocatalytic H2 production from water applications.

Various effects of repeated rifampin dosing on coproporphyrin levels in humans.

In recent years, the identification of endogenous substrates as biomarkers became an uprising topic. Particularly coproporphyrins (CPs), byproducts of heme biosynthesis, are intensely investigated as biomarkers for predicting interactions with the organic anion transporting polypeptide (OATP) 1B transporters. In the context of drug-drug interactions, several preclinical and clinical studies assessed the effect of the OATP1B-index inhibitor rifampin on CPI levels. However, rifampin is not only a "perpetrator" drug of transporters but is also known for its interaction with the nuclear receptor pregnane X receptor (PXR) leading to the efficient induction of PXR-target genes. These include hemoproteins like cytochrome P450 enzymes but also the δ-aminolevulinate synthase 1, which is the rate-limiting enzyme in heme biosynthesis. In this study, we showed that quantification of CPs in clinical serum samples was possible after long-term storage at -20°C. We quantified CPI, CPIII, and heme levels in clinical serum samples (at selected timepoints) that originated from a trial investigating the interaction potential of repeated rifampin administration in 12 healthy participants. In samples collected at the assumed time to maximum concentration of rifampin, higher CP levels were observed compared to baseline. Increased levels persisted even 14 h after discontinuation of rifampin. No impact on heme serum levels was observed. We found a correlation between CP isomers at baseline and at 14 h after rifampin intake. In summary, we show that multiple doses of rifampin affect CP levels. However, besides inhibition of hepatic OATP function there is evidence for an interaction with CP levels beyond the transporter level.

The Fate of Chlorophylls in Alkali-Treated Green Table Olives: A Review.

This paper reviews the current knowledge regarding modifications to chlorophylls during the processing of green table olives treated with alkali. Particular attention is given to the pheophytinization reactions (substitution of Mg2+ by 2H+ in the chlorophyll chromophore group) that can take place because of pH and/or temperature changes and the possible sequential substitution of the 2H+ with Cu2+ within the chlorophyll porphyrin ring. These reactions may have a direct impact on the commercial value of olive productions as some naturally forming Cu-chlorophylls complexes (i) are identical to strictly forbidden colorants for table olives (E141) and (ii) have been identified as responsible for the unwelcome appearance of the so-called green staining alteration (characterized by bluish-green zones distributed over the olive skin of the drupes).