DNA-binding and photocleavage properties of cationic porphyrin–anthraquinone hybrids with different lengths of links

Design, synthesis, antitumor activity and ct-DNA binding study of photosensitive drugs based on porphyrin framework

Photodynamic therapy is a promising novel tumor treatment method. In this study, novel porphyrin-chrysin photosensitizer derivatives were synthesized. Most of the compounds showed antitumor activity against human cervical cancer HeLa cells and human lung cancer A549 cells, among which compound 4c had the best photodynamic therapy effect on HeLa cells and A549 cells, with IC₅₀ values of 6.26 μM and 23.37 μM, respectively. Free-base porphyrin-chrysin derivatives bind to DNA through surface self-stacking, and zinc metalloporphyrin-chrysin derivatives bind to ct-DNA through intercalation. Notably, the tightness of compound binding to ct-DNA was positively correlated with its antitumor activity. What's more, three-dimensional quantitative conformation studies have shown that increasing the positive charge of the porphyrin ring and introducing a strong electron-withdrawing group at the meso position of the porphyrin ring at the para-position of the benzene ring or reducing the space volume of the compound can enhance the antitumor activity.

Hook, Line, and Sinker! Spectroscopic Studies of Bi-Modular Mono- and Bis-1,8-naphthalimide-Ru(bpy)3-conjugates as DNA "Light Switches"

Bi-chromophoric ruthenium polypyridyl complexes comprising one or two nitro-1,8-naphthalimide groups are shown to be effective DNA binders with off-on light switching properties. The binding to DNA was investigated using a combination of studies such as UV-visible absorption and emission titrations, thermal denaturation, and circular dichroism spectroscopy. The DNA affinity was shown to be sensitive to both the linker length and the number of naphthalimides (one vs two) contained in these systems and binding constants ranging from 10⁶ to 10⁷ M^-1 for salmon testes DNA. The strong DNA binding is attributed to the combination of naphthalimide intercalation and the electrostatic interaction of the ruthenium complex. Large emission enhancements from the metal to ligand charge transfer (MLCT) emission arising from the metal complex were observed upon DNA binding, which was attributed to the interruption of intramolecular electron transfer quenching processes. Moving the nitro substitution from the 4-position to the 3-position is found to result in modification of the DNA binding and the resulting optical properties. The off-on light switch phenomena reported demonstrate the potential of these complexes to act as DNA probes.

Interactions of porphyrins with DNA: A review focusing recent advances in chemical modifications on porphyrins as artificial nucleases

The advance of porphyrins as artificial nucleases along the years have developed a class of compounds having potential therapeutic applications. Being an extrovert of chemistry, a variety of chemical modifications have been done on porphyrin macrocycle in order to improve the spectroscopic properties and to adapt as artificial receptors that can recognize molecules. The last twenty years has witnessed broad research in the arena of porphyrin- DNA interactions and their evolution from simple to more complex entities. In this review, we summarize the recent advances in the porphyrin-based structural modifications, with a specific emphasis on various effects of porphyrin on DNA cleavage potency. We particularly detailed the nuclease activity of cationic and anionic porphyrins, porphyrin dimers and conjugates as well as heme proteins till the third generation porphyrins as artificial nucleases.

Synthesis, electrochemistry, DNA binding and in vitro cytotoxic activity of tripodal ferrocenyl bis-naphthalimide derivatives

A series of tripodal ferrocenyl bis-naphthalimide derivatives were synthesized and characterized. All of the bis-naphthalimide derivatives exhibited good DNA binding ability which was confirmed by ethidium bromide (EB) displacement experiment and ultraviolet (UV)-visible absorption titration. And the binding mode of these compounds was proved to be a hybrid binding mode by experiments. The cytotoxicity of synthesized compounds against 4 different human cancer cell lines (EC109, BGC823, SGC7901 and HEPG2) was evaluated by thiazolyl blue tetrazolium bromide (MTT) assay. All of the bis-naphthalimide derivatives exhibited good anticancer activity than the positive control drug (amonafide), which was due to the promotion of reactive oxygen species (ROS) level in test cancer cells by the reversible one-electron redox process of ferrocenyl bis-naphthalimide derivatives. Although there was no obvious relationship between the binding constants and the chain length, the structure cytotoxicity relationship revealed that the linker of n = 3, m = 1 was the best choice for the tested tripodol bis-naphthalimide derivatives. SYNOPSIS: A series of tripodal ferrocenyl bis-naphthalimide derivatives were synthesized to study the DNA binding ability and the cytotoxicity induced by reactive oxygen species. All of the compounds exhibited good DNA binding ability. And the structure cytotoxicity relationship revealed that the structure of 5h was the best choice.

Excitation wavelength dependent ICT character and ISC efficiency in a photocleavage agent of 1-aminoanthraquinone

Anthraquinone derivatives have been widely used as photocleavage agents and dyes. Here, photoinduced excited state intramolecular charge transfer (ICT) dynamics of 1-aminoanthraquinone in ethanol are studied by femtosecond transient absorption (fs-TA) spectroscopy and quantum chemical (QC) calculations. Four decay associated difference spectra and corresponding lifetime components were obtained by singular value decomposition and global fitting analysis from the fs-TA spectra. The QC calculations prove that the S₁ state has obvious ICT character. Planar ICT (PICT) and twisted ICT (TICT) reaction coordinates are observed. On the PICT coordinate, vibrational relaxation (VR) and intersystem crossing (ISC) processes are observed. The ISC efficiency is dependent on excitation wavelength, which elucidates that T'₂ state participates in the ISC process on a higher-level than the S'₁ state. On the TICT coordinate, the TICT process is dependent on excitation wavelength, which elucidates a direct experimental evidence of an energy barrier in excited state TICT potential energy.

A promising anticancer drug: a photosensitizer based on the porphyrin skeleton

Photodynamic therapy (PDT) is a minimally invasive combination of treatments that treat tumors and other diseases by using photosensitizers, light and oxygen to produce cytotoxic reactive oxygen species (ROS) inducing tumor cell apoptosis. Photosensitizers are the key part of PDT for clinical application and experimental research, and most of them are porphyrin compounds at present. Due to their unique affinity for tumor tissues, porphyrins are not only excellent photosensitizers, but also good carriers to transport other active drugs into tumor tissues, which can exert synergistic anticancer effects of PDT and chemotherapy. This article reviews the clinical development of porphyrin photosensitizers and the research status of porphyrin containing bioactive groups. Finally, future perspectives and the current challenges of photosensitizers based on the porphyrin skeleton are discussed.

Sequence selective photoinduced electron transfer of a pyrene-porphyrin dyad to DNA

The binding modes of a pyrene-porphyrin dyad, (1-pyrenyl)-tris(N-methyl-p-pyridino)porphyrin (PyTMpyP), to various DNAs (calf thymus DNA (Ct-DNA), poly[d(G-C)2], and poly[d(A-T)2]) have been investigated using circular dichroism and linear dichroism measurements. Based on the polarization spectroscopic results, it can be shown that the pyrenyl and porphryin planes are skewed to a large extent for PyTMPyP in an aqueous environment and in the binding site of poly[d(G-C)2]. In this complex, a photoinduced electron transfer (PET) process between the pyrenyl and porphyrin moieties occurs. On the other hand, PET was not observed in the PyTMPyP-poly[d(A-T)2] complex, whereas the fluorescence intensity of TMPyP was enhanced. The molecular planes of the pyrene and porphyrin moieties are almost parallel in the poly[d(A-T)2] and Ct-DNA adducts. Moreover, the generation of 1O2 species occurs only for the PyTMPyP-Ct-DNA and PyTMPyP-poly[d(A-T)2] complexes. We discuss the photophysical properties of PyTMPyP which are attributed to the binding patterns and the sequence of DNA bases.

Success stories of natural product-based hybrid molecules for multi-factorial diseases

Complex diseases comprises of highly complicated etiology resulting in limited applicability of conventional targeted therapies. Consequently, conventional medicinal compounds suffer major failure when used for such disease conditions. Additionally, development of multidrug resistance (MDR), adverse drug reactions and clinical specificity of single targeted drug therapy has increased thrust for novel drug therapy. In this rapidly evolving era, natural product-based discovery of hybrid molecules or multi-targeted drug therapies have shown promising results and are trending now a days. Historically, nature has blessed human with different sources viz. plant, animal, microbial, marine and ethnopharmaceutical sources which has given a wide variety of medicinally active compounds. These compounds from natural origin are always choice of interest of medicinal chemists because of their minimum side effects. Hybrid molecules synthesized by fusing or conjugating different active molecules obtained from these sources are reported to synergistically block different pathways which contribute in the pathogenesis of complex diseases. This review strives to encompass all natural product-derived hybrid molecules which act as multi-targeting agents striking various targets involved in different pathways of complex diseased conditions reported in literature.

Relationship between the photoinduced electron transfer and binding modes of a pyrene-porphyrin dyad to DNA

The binding modes of a pyrene-porphyrin dyad, (1-pyrenyl)-tris(N-methyl-p-pyridino)porphyrin (PyTMpyP), to DNA and its photophysical properties have been investigated using various spectroscopic techniques. The circular dichroism (CD) spectrum of PyTMpyP bound to DNA (PyTMpyP-DNA) showed one negative and two positive bands in the Soret region. The CD signal in the pyrene absorption region was positive. The shape of the CD spectrum does not support an intercalative binding mode of TMpyP, which would typically afford a negative CD band in the absence of the pyrene moiety. Linear dichroism (LD) experiments revealed a very small signal in the Soret region, which also challenges the intercalation of TMpyP into DNA. Upon excitation of the pyrene moiety, the emission intensity of porphyrin in aqueous solution was quenched due to a photoinduced electron transfer (PET) process between the pyrenyl and porphyrin moieties. On the other hand, the emission of porphyrin was markedly enhanced upon binding to DNA, as the PET process from the excited pyrene moiety to TMpyP was suppressed when bound to DNA. The PET process occurs in the timescale of 65 ps, and could be detected by femtosecond transient absorption spectroscopic methods. Two fluorescence decay times were observed for PyTMpyP in aqueous solution (0.78 and 4.8 ns). Both decay times increased upon binding to DNA owing to environment and/or conformational changes in PyTMpyP. The driving force (ΔG) of the PET process was evaluated under conditions of minor and major groove binding. The PET process and photophysical properties of the PyTMpyP dyad were concluded to be influenced by the binding mode.

Design and Syntheses of Novel Fluoroporphyrin-Anthraquinone Complexes as Antitumor Agents

A novel fluoroporphyrin-anthraquinone hybrid with dipeptide link and its metal complexes were synthesized and evaluated for anti-proliferation activity in human cancer cell line HeLa. The preliminary results demonstrated that all the compounds showed moderate to excellent antitumor activities. Among the active compounds, compound 3 which contains fluorinated porphyrin-anthraquinone and zinc ion exhibited the highest potency with IC50 value of 8.83 µM, indicating that it was a promising antitumor candidate.

Biological Impact of Pd (II) Complexes: Synthesis, Spectral Characterization, In Vitro Anticancer, CT-DNA Binding, and Antioxidant Activities

A new series of Pd (II) complexes of methyl substituted benzylamine ligands (BLs) has been synthesized and characterized via spectroscopic techniques such as UV/Vis. FTIR, LCMS, ¹H, and ¹³C NMR. The UV/Vis study in DMSO, DMSO + water, and DMSO + PBS buffer (pH = 7.2) confirmed their molecular sustainability in liquids. Their in vitro anticancer activity against breast cancer cell lines such as MCF-7 and MDA-MB-231 makes them interesting for in vivo analysis. Their stronger DNA binding activity (DBA) compared with free ligand suggested them as a good DNA binder. DBA was further confirmed by physicochemical studies such as surface tension and viscosity of complex + DNA which inferred the disruption of DNA and intercalation of complexes, respectively. Their % binding activity, % disruption of DNA base pairs (DNABP), and % intercalating strength are reported in this paper for the first time for better understanding of DNA binding mechanism. Along with this, their scavenging activity (SA) determined through DPPH free radical and the results indicate good antioxidant behaviour of complexes.

Distinguishing binding modes of a new phosphonium dye with DNA by surface-enhanced Raman spectroscopy

SERS spectroscopy provided structural data on binding of a dye as monomer and dimer within minor groove of adenine–thymine polynucleotides.

Synthesis, DNA-binding, and photocleavage properties of a serious of porphyrin-daunomycin hybrids

It is widely accepted that the pharmacological activities of anthracyclines antitumor agents express when the quinone-containing chromophore intercalates into base pairs of the duplex DNA. We have successfully synthesized and investigated the DNA-interactions of hybrids composed with quinone chromophore and cationic porphyrin. Herein, a clinic anticancer drug, daunomycin, is introduced to the porphyrin hybrids through different lengths of amide alkyl linkages, and their interactions and cleavage to DNA were studied compared with the previous porphyrin-quinone hybrids. Spectral results and the determined binding affinity constants (Kb) show that the attachment of daunomycin to porphyrin could improve the DNA-binding and photocleaving abilities. The porphyrin-daunomycin hybrids may find useful employment in investigating the ligand-DNA interaction.

Novel porphyrin-daunomycin hybrids: synthesis and preferential binding to G-quadruplexes over i-motif

Encouraged by the enormous importance attributed to the structure and function of human telomeric DNA, herein we focused our attention on the interaction of a serious of newly prepared porphyrin-daunomycin (Por-DNR) hybrids with the guanine-rich single-strand oligomer (G4) and the complementary cytosine-rich strand (i-motif). Various spectral methods such as absorption and fluorescence titration, surface-enhanced Raman and circular dichroism spectrum were integrated in the experiment and it was found that these Por-DNR hybrids could serve as prominent molecules to recognize G4 and i-motif. What is more, interesting results were obtained that the hybrids with longer flexible links are more favorable in binding with both G4 and i-motif than the hybrid with shorter linkage. These Por-DNR hybrids may help to develop new ideas in the research of human telomeric DNA with small molecules.

Cationic pyridinium porphyrins appending different peripheral substituents: spectroscopic studies on their interactions with bovine serum albumin

The interaction of cationic pyridinium porphyrins appending methylpyridyl, hydroxyphenyl, propionoxyphenyl or carboxyphenyl group at meso-20-position of porphyrin core with bovine serum albumin (BSA), was studied by the combination of absorption spectroscopy, surface-enhanced Raman spectroscopy (SERS), circular dichroism (CD) spectroscopy, fluorescence spectroscopy and synchronous spectroscopy. The spectral monitoring results indicate that the studied compounds could bind with the BSA molecule and the calculated binding constants show that the tetracationic porphyrin has higher binding affinity than those tricationic ones. The interactions between porphyrins and BSA employ an electrostatic binding mechanism and there was only one binding site which located on the surface of the protein molecule.

A Convenient Synthesis of Haematoporphyrin Ester-Ethers under Ultrasound Irradiation

A convenient approach to the synthesis of haematoporphyrin ester-ethers from haemin under ultrasound irradiation has been developed. This method provides several advantages such as shorter reaction time, high yields and environmental friendliness.

DNA binding and photocleavage specificities of a group of tricationic metalloporphyrins

The interactions of 5,10,15-tris(1-methylpyridinium-4-yl)-20-(4-hydroxyphenyl)porphyrinatozinc(II) Zn[TMPyHP](3+) (2) along with Cu[TMPyHP](3+) (3), Co[TMPyHP](4+) (4), Mn[TMPyHP](4+) (5) and the free base porphyrin H(2)[TMPyHP](3+) (1) with duplex DNA have been studied by using a combination of absorption, fluorescence titration, surface-enhanced Raman spectroscopy (SERS), induced circular dichroism (ICD) spectroscopy, thermal DNA denaturation, viscosity measurements as well as gel electrophoresis experiment. Their binding modes and intrinsic binding constants (K(b)) to calf DNA (CT DNA) were comparatively studied and were found significantly influenced by different metals coordinated with the porphyrin plane. Except 3, which has four-coordination structure at the metal, all the metal derivatives showed non-intercalative DNA-binding mode and lower K(b) than the free base porphyrin 1, most probably due to the steric hindrance results from the axial ligands of the inserted metals which are five or six-coordination structures. Meanwhile, the insertion of metals into cationic porphyrin greatly removed the self-aggregation of the metal-free porphyrins, and thus fully enhanced the singlet oxygen ((1)O(2)) productivities in the DNA photocleavage experiments. Therefore, these metalloporphyrins have comparable DNA cleavage ability with the free base porphyrin.