protoporphyrin-IX Dimethyl Ester Research Articles

Synthesis and Characterization of Temperature-Sensitive and Chemically Cross-Linked Poly( N-isopropylacrylamide)/Photosensitizer Hydrogels for Applications in Photodynamic Therapy.

A novel poly( N-isopropylacrylamide) (PNIPAM) hydrogel containing different photosensitizers (protoporphyrin IX (PpIX), pheophorbide a (Pba), and protoporphyrin IX dimethyl ester (PpIX-DME)) has been synthesized with a significant improvement in water solubility and potential for PDT applications compared to the individual photosensitizers (PSs). Conjugation of PpIX, Pba, and PpIX-DME to the poly( N-isopropylacrylamide) chain was achieved using the dispersion polymerization method. This study describes how the use of nanohydrogel structures to deliver a photosensitizer with low water solubility and high aggregation tendencies in polar solvents overcomes these limitations. FT-IR spectroscopy, UV-vis spectroscopy, 1H NMR, fluorescence spectroscopy, SEM, and DLS analysis were used to characterize the PNIPAM-photosensitizer nanohydrogels. Spectroscopic studies indicate that the PpIX, Pba, and PpIX-DME photosensitizers are covalently conjugated to the polymer chains, which prevents aggregation and thus allows significant singlet oxygen production upon illumination. Likewise, the lower critical solution temperature was raised to ∼44 °C in the new PNIPAM-PS hydrogels. The PNIPAM hydrogels are biocompatible with >90% cell viability even at high concentrations of the photosensitizer in vitro. Furthermore, a very sharp onset of light-dependent toxicity for the PpIX-based nanohydrogel in the nanomolar range and a more modest, but significant, photocytotoxic response for Pba-PNIPAM and PpIX-DME-PNIPAM nanohydrogels suggest that the new hydrogels have potential for applications in photodynamic therapy.

Molecular Features of the YAP Inhibitor Verteporfin: Synthesis of Hexasubstituted Dipyrrins as Potential Inhibitors of YAP/TAZ, the Downstream Effectors of the Hippo Pathway

Porphyrin derivatives, in particular verteporfin (VP), a photosensitizer initially designed for cancer therapy, have been identified as inhibitors of the YAP-TEAD interaction and transcriptional activity. Herein we report the efficient convergent synthesis of the dipyrrin half of protoporphyrin IX dimethyl ester (PPIX-DME), in which the sensitive vinyl group was created at the final stage by a dehydroiodination reaction. Two other dipyrrin derivatives were synthesized, including dipyrrin 19 [(Z)-2-((3,5-dimethyl-4-vinyl-2H-pyrrol-2-ylidene)methyl)-3,5-dimethyl-4-vinyl-1H-pyrrole], containing two vinyl groups. We found that VP and dipyrrin 19 showed significant inhibitory effects on TEAD transcriptional activity in MDA-MB-231 human breast cancer cells, whereas other compounds did not show significant changes. In addition, we observed a marked decrease in both YAP and TAZ levels following VP treatment, whereas dipyrrin 19 treatment primarily decreased the levels of YAP and receptor kinase AXL, a downstream target of YAP. Together, our data suggest that, due to their chemical structures, porphyrin- and dipyrrin-related derivatives can directly target YAP and/or TAZ proteins and inhibit TEAD transcriptional activity.

The effect of porphyrin structure on binding to human serum albumin by fluorescence spectroscopy

The efficacy of porphyrin binding to human serum albumin (HSA) is critical to clinical use in photodynamic therapy (PDT). Several porphyrins were utilized to measure the effect of porphyrin structure on its binding to HSA. Two categories of porphyrins were utilized: porphyrins with a hydrophobic and hydrophilic side: Protoporphyrin IX (PPIX), Protoporphyrin IX dimethylester (PPIXDE), and Chlorin e 6 (Ce6) and porphyrins with hydrophilic substituents on both sides: Hematoporphyrin IX (Hme), Hematoporphyrin IX dimethylester (HmeDE), and Deuteroporphyrin IX dimethylester (DPIXEG). The following methods were used for the analysis: Stern–Volmer quenching, fluorescence lifetimes, anisotropy, fluorescence binding, and homogeneous studies. The results indicate that PPIX, PPIXDE, and Ce6 bind to HSA efficiently, evidence that porphyrins bind strongly to HSA if they have a hydrophobic and hydrophilic side. Hme is thought to bind to HSA but likely to a lesser degree than the aforementioned three porphyrins. HmeDE and DPIXEG seem not to bind to HSA probably due to the lack of hydrophobic substituents.

Synthesis of new amphiphilic chlorin derivatives from protoporphyrin-IX dimethyl ester

A simple synthesis of new amphiphilic chlorin derivatives from protoporphyrin-IX dimethyl ester is reported. The preparation of such compounds is based in a straightforward methodology, which involves the Diels–Alder reaction of protoporphyrin-IX dimethyl ester with maleic anhydride followed by addition of nucleophilic species to the initially formed cycloadducts, a transformation, which is highly regioselective. Preliminary photophysical studies with the new compounds show that they meet adequate features for PDT applications.

A Comparison of Protoporphyrin IX and Protoporphyrin IX Dimethyl Ester as a Photosensitizer in Poorly Differentiated Human Nasopharyngeal Carcinoma Cells¶

Protoporphyrin IX dimethyl ester (PME), a dimethyl esterification of protoporphyrin IX (PpIX), exhibits higher intracellular uptake into NPC/CNE2 cells, a poorly differentiated human nasopharyngeal carcinoma, than does PpIX. Phototoxicity studies reveal PME to be a more potent photosensitizer than is PpIX, at the early and late incubation time points. Correlating phototoxicity with subcellular localization indicates that PME is a more potent photosensitizer when its primary target of photodamage is mitochondria. Also, additional targeting of lysosome enhances phototoxicity.

An evaluation of exogenous application of protoporphyrin IX and its dimethyl ester as a photodynamic diagnostic agent in poorly differentiated human nasopharyngeal carcinoma.

5-Aminolevulinic acid and its esterified analogues have been under much investigation to enhance the endogenous production of protoporphyrin IX (PpIX) in tumor cells. However, in this work, we studied the in vitro and in vivo efficacy of exogenously administered PpIX and its esterified analogue, PpIX dimethyl ester (PME), in poorly differentiated human nasopharyngeal carcinoma (NPC/CNE-2) as a photodynamic diagnostic (PDD) agent. NPC/CNE-2 at its earliest time, 1 h after incubation with PME in in vitro studies, has exhibited 64% (P <0.01) higher tumor to normal cell (T/N) fluorescence ratio than with PpIX. In an in vivo mouse xenograft model, comparable photosensitizer concentration in tumor after intravenous administration was observed at 1-3 h time points, but at 9 h, PME had 31% (P=0.05) greater concentration in tumor compared with PpIX. In addition, by constituting PME and PpIX in different topical gel composites, of which, PME gel composition of 8:2 Plasdone and Gantrez resulted in the highest T/N ratio at 6 h after application (34%; P <0.05) in comparison with other gel composites. Evaluation of PME and PpIX constituted in the delivery vehicles investigated showed comparable selectivity for tumor at 1-3 h, thus neither photosensitizer is more efficient than the other for PDD at the early time points; however, beyond 6 h, PME had higher selectivity for tumor compared with PpIX. Thus, further investigation is warranted to improve the drug delivery vehicle for greater tumor selectivity at a shorter incubation time.

A study comparing endogenous protoporphyrin IX induced by 5-ALA and ALA-methyl ester with exogenous PpIX and PpIX dimethyl ester in photodynamic diagnosis of human nasopharyngeal carcinoma xenografts

5-Aminolevulinic acid (5-ALA) and its esters have been under intense investigation to enhance the endogenous production of protoporphyrin IX (PpIX) in tumour cells for the purpose of photodynamic diagnosis. In this study we have investigated the use of exogenous PpIX and its dimethyl ester (PME) and compared the results with endogenous PpIX produced via 5-ALA and ALA methyl ester (AME) in poorly differentiated NPC/CNE-2 nasopharyngeal carcinoma cells in both in vivo and in vitro systems. All prodrugs and photosensitizers were administered to tumour bearing balb/c nude mice either intravenously or topically. in vitro results show that 5-ALA induced more PpIX fluorescence when compared with AME in NPC/CNE-2 cells and PME showed better uptake than PpIX. in vivo results show that exogenous PpIX and PME show promise as good candidates as photosensitizers for photodynamic diagnosis as they exhibit significant selectivity between tumour tissue and normal tissue at 3 h. Modification of delivery vehicle used for application of exogenous PpIX and PME could allow for rapid uptake; better selectivity and localization of the photosensitizer.

Improving regioselectivity in the rhodium catalyzed hydroformylation of protoporphyrin-IX and chlorophyll a derivatives

An efficient and selective catalytic process to promote the hydroformylation of protoporphyrin-IX dimethyl ester, the respective nickel(II) and zinc(II) complexes and also of methyl pheophorbide a allomer is described. The effect of the central metal ion, pressure, temperature and phosphine ligand structure on the regioselectivity of the reactions is discussed and molecular PM3 calculations are presented in order to rationalize these effects. The hydroformylation reaction of protoporphyrin-IX dimethyl ester using triphenylphosphine (PPh 3) as ligand, at 30 bar and 31 °C yielded 98% of branched aldehyde. However, using 9,9-dimethyl-4,6-bis(diphenylphosphino)xanthene (Xantphos), as ligand, at 20 bar and 80 °C, 74% of linear aldehyde was observed. The regioselectivity of the reaction is strongly dependent on the central metal ion. The zinc(II) complex of protoporphyrin-IX dimethyl ester favours the formation of the branched aldehyde (99%) independently of reaction conditions, while the regioselectivity with the nickel(II) complex showed a dependence both on pressure and temperature. The hydroformylation of methyl pheophorbide a allomer yields 98% of the branched aldehyde even at 20 bar and 80 °C reaction conditions.

An Evaluation of Exogenous Application of Protoporphyrin IX and its Dimethyl Ester as a Photodynamic Diagnostic Agent in Poorly Differentiated Human Nasopharyngeal Carcinoma¶

Abstract5‐Aminolevulinic acid and its esterified analogues have been under much investigation to enhance the endogenous production of protoporphyrin IX (PpIX) in tumor cells. However, in this work, we studied the in vitro and in vivo efficacy of exogenously administered PpIX and its esterified analogue, PpIX dimethyl ester (PME), in poorly differentiated human nasopharyngeal carcinoma (NPC/CNE‐2) as a photodynamic diagnostic (PDD) agent. NPC/CNE‐2 at its earliest time, 1 h after incubation with PME in in vitro studies, has exhibited 64% (P &lt; 0.01) higher tumor to normal cell (T/N) fluorescence ratio than with PpIX. In an in vivo mouse xenograft model, comparable photosensitizer concentration in tumor after intravenous administration was observed at 1–3 h time points, but at 9 h, PME had 31% (P = 0.05) greater concentration in tumor compared with PpIX. In addition, by constituting PME and PpIX in different topical gel composites, of which, PME gel composition of 8:2 Plasdone® and Gantrez® resulted in the highest T/N ratio at 6 h after application (34%; P &lt; 0.05) in comparison with other gel composites. Evaluation of PME and PpIX constituted in the delivery vehicles investigated showed comparable selectivity for tumor at 1–3 h, thus neither photosensitizer is more efficient than the other for PDD at the early time points; however, beyond 6 h, PME had higher selectivity for tumor compared with PpIX. Thus, further investigation is warranted to improve the drug delivery vehicle for greater tumor selectivity at a shorter incubation time.

An Evaluation of Exogenous Application of Protoporphyrin IX and its Dimethyl Ester as a Photodynamic Diagnostic Agent in Poorly Differentiated Human Nasopharyngeal Carcinoma ¶

5-Aminolevulinic acid and its esterified analogues have been under much investigation to enhance the endogenous production of protoporphyrin IX (PpIX) in tumor cells. However, in this work, we studied the in vitro and in vivo efficacy of exogenously administered PpIX and its esterified analogue, PpIX dimethyl ester (PME), in poorly differentiated human nasopharyngeal carcinoma (NPC/CNE-2) as a photodynamic diagnostic (PDD) agent. NPC/CNE-2 at its earliest time, 1 h after incubation with PME in in vitro studies, has exhibited 64% (P <0.01) higher tumor to normal cell (T/N) fluorescence ratio than with PpIX. In an in vivo mouse xenograft model, comparable photosensitizer concentration in tumor after intravenous administration was observed at 1-3 h time points, but at 9 h, PME had 31% (P=0.05) greater concentration in tumor compared with PpIX. In addition, by constituting PME and PpIX in different topical gel composites, of which, PME gel composition of 8:2 Plasdone and Gantrez resulted in the highest T/N ratio at 6 h after application (34%; P <0.05) in comparison with other gel composites. Evaluation of PME and PpIX constituted in the delivery vehicles investigated showed comparable selectivity for tumor at 1-3 h, thus neither photosensitizer is more efficient than the other for PDD at the early time points; however, beyond 6 h, PME had higher selectivity for tumor compared with PpIX. Thus, further investigation is warranted to improve the drug delivery vehicle for greater tumor selectivity at a shorter incubation time.

An Evaluation of Exogenous Application of Protoporphyrin IX and its Dimethyl Ester as a Photodynamic Diagnostic Agent in Poorly Differentiated Human Nasopharyngeal Carcinoma ¶

5-Aminolevulinic acid and its esterified analogues have been under much investigation to enhance the endogenous production of protoporphyrin IX (PpIX) in tumor cells. However, in this work, we studied the in vitro and in vivo efficacy of exogenously administered PpIX and its esterified analogue, PpIX dimethyl ester (PME), in poorly differentiated human nasopharyngeal carcinoma (NPC/CNE-2) as a photodynamic diagnostic (PDD) agent. NPC/CNE-2 at its earliest time, 1 h after incubation with PME in in vitro studies, has exhibited 64% (P < 0.01) higher tumor to normal cell (T/N) fluorescence ratio than with PpIX. In an in vivo mouse xenograft model, comparable photosensitizer concentration in tumor after intravenous administration was observed at 1–3 h time points, but at 9 h, PME had 31% (P = 0.05) greater concentration in tumor compared with PpIX. In addition, by constituting PME and PpIX in different topical gel composites, of which, PME gel composition of 8:2 Plasdone® and Gantrez® resulted in the highest T/N ratio at 6 h after application (34%; P < 0.05) in comparison with other gel composites. Evaluation of PME and PpIX constituted in the delivery vehicles investigated showed comparable selectivity for tumor at 1–3 h, thus neither photosensitizer is more efficient than the other for PDD at the early time points; however, beyond 6 h, PME had higher selectivity for tumor compared with PpIX. Thus, further investigation is warranted to improve the drug delivery vehicle for greater tumor selectivity at a shorter incubation time.

Hydroformylation: a versatile tool for the synthesis of new β-formyl-metalloporphyrins

Formyl derivatives of protoporphyrin-IX dimethyl ester metal complexes were obtained via hydroformylation reactions, catalysed by rhodium–triphenylphosphine complexes. The regioselectivity of the reaction is remarkably dependent on the metal centre of the porphyrin, yielding 100% of the branched aldehyde with zinc(II) complexes and 75% with the nickel(II). The NMR characterisation of the new compounds was carried out after their derivatisation into acetals.

Factors Affecting the Electronic Ground State of Low-Spin Iron(III) Porphyrin Complexes

To determine the factors affecting the ground-state electron configuration of low-spin Fe(III) porphyrin complexes, we have examined the (1)H NMR, (13)C NMR, and EPR spectra of a series of low-spin bis-ligated Fe(III) porphyrin complexes [Fe(Por)L(2)](+/-), in which the positions of porphyrin substituents and the coordination ability of axial ligands are different. The seven porphyrins used in this study are meso-tetraalkylporphyrins (TRP: R is propyl, cyclopropyl, or isopropyl), meso-tetraphenylporphyrin (TPP), meso-tetrakis(2,3,4,5,6-pentafluorophenyl)porphyrin, and 5,10,15,20-tetraphenyl-2,3,7,8,12,13,17,18-octaalkylporphyrins (ORTPP: R is methyl or ethyl). The porphyrin cores of TRP are more or less S(4)-ruffled depending on the bulkiness of the alkyl substituents, while those of ORTPP are highly S(4)-saddled. Three types of axial ligands are examined which have the following characteristics in ligand field theory: they are (i) strong sigma-donating imidazole (HIm), (ii) strong sigma-donating and weak pi-accepting cyanide (CN(-)), and (iii) weak sigma-donating and strong pi-accepting tert-butyl isocyanide ((t)BuNC). In the case of the bis(HIm) complexes, only the isopropyl complex, [Fe(T(i)PrP)(HIm)(2)](+), has shown the less common (d(xz), d(yz))(4)(d(xy))(1) ground state; the other six complexes have exhibited the common (d(xy))(2)(d(xz), d(yz))(3) ground state. When the axial imidazole is replaced by cyanide, even the propyl and cyclopropyl complexes have shown the (d(xz), d(yz))(4)(d(xy))(1) ground state; the TPP and ORTPP complexes have still maintained the common (d(xy))(2)(d(xz), d(yz))(3) ground state. In the case of the bis((t)()BuNC) complexes, all the complexes have shown the (d(xz), d(yz))(4)(d(xy))(1) ground state. However, the contribution of the (d(xz), d(yz))(4)(d(xy))(1) state to the electronic ground state differs from complex to complex; the (d(xz), d(yz))(4)(d(xy))(1) contribution is the largest in [Fe(T(i)PrP)((t)()BuNC)(2)](+) and the smallest in [Fe(OETPPP)((t)BuNC)(2)](+). We have then examined the electronic ground state of low-spin [Fe(OEP)((t)BuNC)(2)](+) and [Fe(ProtoIXMe(2))((t)BuNC)(2)](+); OEP and ProtoIXMe(2) represent 2,3,7,8,12,13,17,18-octaethylporphyrin and protoporphyrin-IX dimethyl ester, respectively. These porphyrins have a(1u) HOMO in contrast to the other seven porphyrins that have a(2u) HOMO. The (13)C NMR and EPR studies have revealed that the contribution of the (d(xz), d(yz))(4)(d(xy))(1) state in these complexes is as small as that in [Fe(OETPP)((t)BuNC)(2)](+). On the basis of these results, we have concluded that the low-spin iron(III) porphyrins that have (i) strong axial ligands, (ii) highly saddle shaped porphyrin rings, (iii) porphyrins with a(1u) HOMO, and (iv) electron withdrawing substituents at the meso positions tend to maintain the common (d(xy))(2)(d(xz), d(yz))(3) ground state.

New Heck-Type Reaction Applied to the Synthesis of Protoporphyrin-IX Derivatives

[reaction: se text] A new Heck-type reaction under catalysis by Pd for obtaining polysubstituted arylvinylydene derivatives of porphyrin systems is reported. The coupling between the Zn(II)-protoporphyrin-IX dimethylester Zn-2 and several bromo-aryl and iodo-aryl compounds in the presence of a new Pd catalyst has been studied. This coupling reaction, although providing moderate regioselectivity, gives quantitative conversion.

Haem propionates control oxidative and reductive activities of horseradish peroxidase by maintaining the correct orientation of the haem.

The role of haem propionates in oxidative and reductive reactions catalysed by horseradish peroxidase (HRP) was studied after successful reconstitution of ferric protoporphyrin IX dimethyl ester (PPDME) into the apoperoxidase. The reconstituted enzyme oxidizes neither guaiacol (aromatic electron donor) nor iodide or thiocyanate (inorganic donor). Although the reconstituted enzyme binds guaiacol with a similar Kd (13 mM) to that of the native enzyme (10 mM), the Kd for SCN- binding (5 mM) is decreased 20-fold compared with that of the native enzyme (100 mM). This indicates that haem propionates hinder the entry or binding of inorganic anion to the active site of the native HRP. However, the reconstituted enzyme is catalytically inactive as it does not form spectroscopically detectable compound II with H2O2. CD measurements indicate a significant loss of haem CD spectrum of the reconstituted enzyme at 409 nm, suggesting a loss of asymmetry of the haem-protein interaction. Thus the inability of the reconstituted enzyme to form catalytic intermediates results from the change in orientation of the haem due to loss of interactions via the haem propionates. HRP also catalyses reductive reactions such as reduction of iodine (I+) in the presence of EDTA and H2O2. The reconstituted enzyme cannot catalyse I+ reduction because of the loss of I+ binding to the haem propionate. Since I+ reduction requires formation of the catalytically active enzyme-I+-EDTA ternary complex, the loss of reductive activity is primarily due to the loss of active enzyme formation. Haem propionates thus play a vital role in the oxidative and reductive reactions of HRP by favouring the formation of catalytic intermediates with H2O2 by maintaining the correct orientation of the haem with respect to the surrounding residues.

The Effect of the Irradiation Wavelength on the Processes Sensitized by Protoporphyrin IX Dimethyl Ester

The formation of triplet states of photosensitizers and singlet oxygen during reactions sensitized by protoporphyrin IX dimethyl ester (PPDME) and the products of its photo-oxidation in solution were studied by time-resolved spectroscopy. Irradiation with long-wavelength light (670 nm), which is absorbed by the products of photo-oxidation of PPDME, provides lower quantum yields of singlet oxygen than in sensitization with PPDME alone, which absorbs light with a wavelength of 630 nm. Spectroscopic measurements also confirmed the lower rate of sensitized photo-oxidation of bilirubin during irradiation with light with a wavelength of 670 nm.

Syntheses of oxygen analogues of sulfhemes-A and -C

Syntheses of-metal-free oxygen analogues of the sulfhemes-A and -C from protoporphyrin-IX dimethyl ester 1 are presented. Oxasulfporphyrin-C dimethyl ester 5 is obtained by intramolecular displacement of a primary rosylate by a tertiary hydroxyl in an appropriately constructed precursor 18, or by surface-catalyzed rearrangement of the epoxide-bearing oxasulfporphyrin-A dimethyl ester 23. Compound 23 is in turn prepared by Mitsunobu type internal dehydration of the precursor 12. The methodology is then successfully extended to more symmetric porphyrin systems. Compounds 23, 25, 46, and 61/ 62 are the first porphyrin epoxides to be synthesized.

Alkylpyrroles in a kerogen pyrolysate: Evidence for abundant tetrapyrrole pigments

C 1-C 6 alkylated pyrroles were identified as major constituents of the flash pyrolysate of a kerogen from the Miocene Monterey Formation (California, USA) using gas chromatography with an N-selective detector and gas chromatography-mass spectrometry. The major alkylpyrroles identified are 2,3,4-trimethylpyrrole; 3-ethyl-4-methylpyrrole; 2,3-dimethyl-4-ethylpyrrole; 2,4-dimethyl-3-ethylpyrrole; and 3-ethyl-2,4,5-trimethylpyrrole. The alkyl substitution patterns of the alkylpyrroles strongly suggest an origin from tetrapyrrole pigments. Evidence for this hypothesis was provided by flash pyrolysis of the tetrapyrrole pigments chlorophyll- a, protoporphyrin-IX dimethyl ester, and bilirubin, which yielded alkylpyrroles with a similar isomer distribution. Quantitative pyrolysis using a polymer internal standard of both the kerogen and the tetrapyrrole pigments revealed that ca. 5% of the kerogen consists of macromolecularly bound tetrapyrrole pigments or that this fraction contains ca. 5% insoluble tetrapyrrole salts. These results show that in specific cases tetrapyrrole pigments can contribute significantly to the sedimentary organic matter.

Radical intermediates induced by porphyrin triplets

In the photochemical reactions of triplets of both protoporphyrin-IX-dimethyl-ester (PP) and haematoporphyrin dihydrochloride (HP) with α-phenyl-ethyl hydroperoxide (HROOH) in C 6H 6 at room temperature, both OO and CC bonds are broken yielding alkoxy and carbon-centred radicals. The ruptures of CC and OH bonds were observed in the photochemical reaction of PP with tert-butanol in the same solvent, yielding alkoxy and carbon-centred radicals at λ⩾ 366 nm, while HP did not react photochemically with tert-butanol at λ⩾334 nm.

Synthesis of oxygen analogues of the sulfchlorins

The oxygen analogues of sulfchlorin-A and-C were synthesized from protoporphyrin-IX dimethyl ester. The developed methodology employs a modified Mitsunobu reaction and produces the first porphyrin epoxides and porphyrinones derived from protoporphyrin-IX.