Singlet Oxygen Quencher Research Articles

Heterologous expression of cyanobacterial Orange Carotenoid Protein (OCP2) as a soluble carrier of ketocarotenoids in Chlamydomonas reinhardtii

Photosynthetic organisms evolved different mechanisms to protect themselves from high irradiances and photodamage. In cyanobacteria, the photoactive Orange Carotenoid-binding Protein (OCP) acts both as a light sensor and quencher of excitation energy. It binds keto-carotenoids and, when photoactivated, interacts with phycobilisomes, thermally dissipating the excitation energy absorbed by the latter, and acting as efficient singlet oxygen quencher. Here, we report the heterologous expression of an OCP2 protein from the thermophilic cyanobacterium Fischerella thermalis (FtOCP2) in the model organism for green algae, Chlamydomonas reinhardtii. Robust expression of FtOCP2 was obtained through a synthetic redesigning strategy for optimized expression of the transgene. FtOCP2 expression was achieved both in UV-mediated mutant 4 strain, previously selected for efficient transgene expression, and in a background strain previously engineered for constitutive expression of an endogenous β-carotene ketolase, normally poorly expressed in this species, resulting into astaxanthin and other ketocarotenoids accumulation. Recombinant FtOCP2 was successfully localized into the chloroplast. Upon purification it was possible to demonstrate the formation of holoproteins with different xanthophylls and ketocarotenoids bound, including astaxanthin. Moreover, isolated ketocarotenoid-binding FtOCP2 holoproteins conserved their photoconversion properties. Carotenoids bound to FtOCP2 were thus maintained in solution even in absence of organic solvent. The synthetic biology approach herein reported could thus be considered as a novel tool for improving the solubility of ketocarotenoids produced in green algae, by binding to water-soluble carotenoids binding proteins.

Blue Light Treatment but Not Green Light Treatment After Pre-exposure to UV-B Stabilizes Flavonoid Glycoside Changes and Corresponding Biological Effects in Three Different Brassicaceae Sprouts

Ultraviolet-B (UV-B; 280–315 nm) radiation induces the biosynthesis of secondary plant metabolites such as flavonoids. Flavonoids could also be enhanced by blue (420–490 nm) or green (490–585 nm) light. Flavonoids act as antioxidants and shielding components in the plant’s response to UV-B exposure. They are shown to quench singlet oxygen and to be reactive to hydroxyl radical. The aim was to determine whether treatment with blue or green light can alter flavonoid profiles after pre-exposure to UV-B and whether they cause corresponding biological effects in Brassicaceae sprouts. Based on their different flavonoid profiles, three vegetables from the Brassicaceae were selected. Sprouts were treated with five subsequent doses (equals 5 days) of moderate UV-B (0.23 kJ m–2 day–1 UV-BBE), which was followed with two subsequent (equals 2 days) doses of either blue (99 μmol m–2 s–1) or green (119 μmol m–2 s–1) light. In sprouts of kale, kohlrabi, and rocket salad, flavonoid glycosides were identified by HPLC-DAD-ESI-MSn. Both Brassica oleracea species, kale and kohlrabi, showed mainly acylated quercetin and kaempferol glycosides. In contrast, in rocket salad, the main flavonol glycosides were quercetin glycosides. Blue light treatment after the UV-B treatment showed that quercetin and kaempferol glycosides were increased in the B. oleracea species kale and kohlrabi while—contrary to this—in rocket salad, there were only quercetin glycosides increased. Blue light treatment in general stabilized the enhanced concentrations of flavonoid glycosides while green treatment did not have this effect. Blue light treatment following the UV-B exposure resulted in a trend of increased singlet oxygen scavenging for kale and rocket. The hydroxyl radical scavenging capacity was independent from the light quality except for kale where an exposure with UV-B followed by a blue light treatment led to a higher hydroxyl radical scavenging capacity. These results underline the importance of different light qualities for the biosynthesis of reactive oxygen species that intercept secondary plant metabolites, but also show a pronounced species-dependent reaction, which is of special interest for growers.

Carotenoids, Vitamin C, and Antioxidant Capacity in the Peel of Mandarin Fruit in Relation to the Susceptibility to Chilling Injury during Postharvest Cold Storage.

Chilling injury (CI) is a postharvest disorder occurring in the fruit of cold-sensitive Citrus species during storage at low temperatures. This study investigated the involvement of carotenoids and vitamin C, two major antioxidants of citrus peel, and the antioxidant capacity in the CI susceptibility of mandarin fruit. To that end, the fruit of three commercial varieties, Fortune, Nova, and Nadorcott, with significant differences in CI susceptibility, were selected. By on-tree fruit bagging, carotenoids and vitamin C contents were modified, and a differential effect of each cultivar on CI was observed. Carotenoid analysis in the peel revealed a strong negative correlation between total carotenoid concentration (TCC) at harvest, and specifically of β-cryptoxanthin and violaxanthin, and CI index at the end of storage. In contrast, vitamin C content was significantly and positively correlated with CI susceptibility. The antioxidant activity assessed by the DPPH• and FRAP reflected the contribution of vitamin C to the antioxidant system, while the SOAC assay correlated positively with TTC, β-cryptoxanthin, and violaxanthin. Collectively, the antioxidant capacity of carotenoids at harvest, as efficient singlet oxygen quenchers, suggests a protective role against the development of CI in mandarin fruit, while vitamin C is not likely playing a critical role.

Correction to: Quenching of singlet oxygen by natural and synthetic antioxidants and assessment of electronic UV/Visible absorption spectra for alleviating or enhancing the efficacy of photodynamic therapy

The original article1 contains an error in the author affiliation. The author affiliation is corrected as below:
 Kaneez Fatima1;2, Nusrat Masood1, Suaib Luqman1;2
 1CSIR-Central Institute of Medicinal and Aromatic Plants, Lucknow-226015, Uttar Pradesh, India2Academy of Scientific and Innovative Research (AcSIR), Ghaziabad-201002, Uttar Pradesh, India
 REFERENCES
 1. Fatima K, Masood N, Luqman S. Quenching of singlet oxygen by natural and synthetic antioxidants and assessment of electronic UV/Visible absorption spectra for alleviating or enhancing the efficacy of photodynamic therapy. Biomedical Research and Therapy. 2016;3(2):514–527.

The Influence of Heating and Photosensitization on the Stability of Lutein- Loaded Lipid-Core Nanocapsules

Background: Despite lutein is unstable in light, heat, and oxygen, it is a good quencher of singlet oxygen. The present study evaluated the stability of lutein (92% of purity) in Lipid-core Nanocapsules (Lutein-LNC) prepared through interfacial deposition of preformed polymer, during photosensitization (5-25°C) and heating (70-90°C). Methods: The Lutein-LNC was characterized and presented a polydispersity index of 0.11, an average diameter of 191 nm (dynamic light scattering), zeta potential of -9.14 mV and entrapment efficiency of 100%. Results and Discussion: During photosensitization and heating, Lutein-LNC exhibited activation Energy (Ea) of 24.67 kcal/mol and 9.96 kcal/mol, respectively, and these values of Lutein-LNC were higher than free lutein values, reported in other studies for both experiments. Conclusion: The results obtained in this study suggested that nanotechnology can improve the stability of lutein for future applications in the food industry.

Redox Potential of Antioxidants in Cancer Progression and Prevention.

The benevolent and detrimental effects of antioxidants are much debated in clinical trials and cancer research. Several antioxidant enzymes and molecules are overexpressed in oxidative stress conditions that can damage cellular proteins, lipids, and DNA. Natural antioxidants remove excess free radical intermediates by reducing hydrogen donors or quenching singlet oxygen and delaying oxidative reactions in actively growing cancer cells. These reducing agents have the potential to hinder cancer progression only when administered at the right proportions along with chemo-/radiotherapies. Antioxidants and enzymes affect signal transduction and energy metabolism pathways for the maintenance of cellular redox status. A decline in antioxidant capacity arising from genetic mutations may increase the mitochondrial flux of free radicals resulting in misfiring of cellular signalling pathways. Often, a metabolic reprogramming arising from these mutations in metabolic enzymes leads to the overproduction of so called ’oncometabolites’ in a state of ‘pseudohypoxia’. This can inactivate several of the intracellular molecules involved in epigenetic and redox regulations, thereby increasing oxidative stress giving rise to growth advantages for cancerous cells. Undeniably, these are cell-type and Reactive Oxygen Species (ROS) specific, which is manifested as changes in the enzyme activation, differences in gene expression, cellular functions as well as cell death mechanisms. Photodynamic therapy (PDT) using light-activated photosensitizing molecules that can regulate cellular redox balance in accordance with the changes in endogenous ROS production is a solution for many of these challenges in cancer therapy.

Proline is a quencher of singlet oxygen and superoxide both in in vitro systems and isolated thylakoids.

Proline is a versatile plant metabolite, which is produced in large amounts in plants exposed to osmotic and oxidative stress. Proline has been shown to provide protection against various reactive oxygen species (ROS), such as hydrogen peroxide and hydroxyl radicals. On the other hand, its protective effect against singlet oxygen has been debated, and it is considered ineffective against superoxide. Here we used various methods for the detection of singlet oxygen (electron paramagnetic resonance, EPR, spin trapping by 2,2,6,6-tetramethyl-4-piperidone, fluorescence probing by singlet oxygen sensor green, SOSG, and oxygen uptake due to chemical trapping) and superoxide (oxygen uptake due to oxygen reduction) in vitro and in isolated thylakoids. We demonstrated that proline does quench both singlet oxygen and superoxide in vitro. By comparing the effects of chemical scavengers and physical quenchers, we concluded that proline eliminates singlet oxygen via a physical mechanism, with a bimolecular quenching rate of ca. 1.5-4 106 M-1 s-1 . Our data also show that proline can eliminate superoxide in vitro in a process that is likely to proceed via an electron transfer reaction. We could also show that proline does quench both singlet oxygen and superoxide produced in isolated thylakoids. The scavenging efficiency of proline is relatively small on a molar basis, but considering its presence in high amounts in plant cells under stress conditions it may provide a physiologically relevant contribution to ROS scavenging, supplementing other nonenzymatic ROS scavengers of plant cells.

Appropriate Technologies to Accompany Sunscreens in the Battle Against Ultraviolet, Superoxide, and Singlet Oxygen.

The interaction of ultraviolet radiation with biological matter results in direct damage such as pyrimidine dimers in DNA. It also results in indirect damage provoked by the production of reactive oxygen species (ROS) catalyzed by photosensitizers. Photosensitizers can be endogenous (e.g., tryptophan) or exogenous (e.g., TiO2 and other photostable UVA sunscreens). Direct damage triggers an inflammatory response and the oxidative and proteolytic bursts that characterize its onset. The inflammatory reaction multiplies the effects of one single photon. Indirect damage, such as the peroxidative cascade in membrane lipids, can extend to thousands of molecular modifications per absorbed photon. Sunscreens should therefore be formulated in the presence of appropriate antioxidants. Superoxide and singlet oxygen are the main ROS that need to be tackled: this review describes some of the molecular, biochemical, cellular, and clinical consequences of exposure to UV radiation as well as some results associated with scavengers and quenchers of superoxide and singlet oxygen, as well as with inhibitors of singlet oxygen production.

Photooxidation Activity Control of Dimethylaminophenyl-tris-(N-methyl-4-pridinio)porphyrin by pH.

To control the activity of photodynamic agents by pH, an electron donor-connecting cationic porphyrin, meso-(N′,N′-dimethyl-4-aminophenyl)-tris(N-methyl-p-pyridinio)porphyrin (DMATMPyP), was designed and synthesized. The photoexcited state (singlet excited state) of DMATMPyP was deactivated through intramolecular electron transfer under a neutral condition. The pKa of the protonated DMATMPyP was 4.5, and the fluorescence intensity and singlet oxygen-generating activity increased under an acidic condition. Furthermore, the protonation of DMATMPyP enhanced the biomolecule photooxidative activity through electron extraction. Photodamage of human serum albumin (HSA) was observed under a neutral condition because a hydrophobic HSA environment can reverse the deactivation of photoexcited DMATMPyP. However, an HSA-damaging mechanism of DMATMPyP under a neutral condition was explained by singlet oxygen production. Therefore, it is indicated that the protein photodamaging activity of DMATMPyP goes into an OFF state under a neutral hypoxic condition. Under an acidic condition, the HSA photodamaging quantum yield by DMATMPyP through electron extraction could be preserved in the presence of a singlet oxygen quencher. Photooxidation of nicotinamide adenine dinucleotide by DMATMPyP was also enhanced under an acidic condition. This study demonstrated the concept of using pH to control photosensitizer activity via inhibition of the intramolecular electron transfer deactivation and enhancement of the oxidative activity through the electron extraction mechanism. Specifically, biomolecule oxidation through electron extraction may play an important role in photodynamic therapy to treat tumors under a hypoxic condition.

Oxidative stress mitigation by antioxidants - An overview on their chemistry and influences on health status.

The present review paper focuses on the chemistry of oxidative stress mitigation by antioxidants. Oxidative stress is understood as a lack of balance between the pro-oxidant and the antioxidant species. Reactive oxygen species in limited amounts are necessary for cell homeostasis and redox signaling. Excessive reactive oxygenated/nitrogenated species production, which counteracts the organism's defense systems, is known as oxidative stress. Sustained attack of endogenous and exogenous ROS results in conformational and oxidative alterations in key biomolecules. Chronic oxidative stress is associated with oxidative modifications occurring in key biomolecules: lipid peroxidation, protein carbonylation, carbonyl (aldehyde/ketone) adduct formation, nitration, sulfoxidation, DNA impairment such strand breaks or nucleobase oxidation. Oxidative stress is tightly linked to the development of cancer, diabetes, neurodegeneration, cardiovascular diseases, rheumatoid arthritis, kidney disease, eye disease. The deleterious action of reactive oxygenated species and their role in the onset and progression of pathologies are discussed. The results of oxidative attack become themselves sources of oxidative stress, becoming part of a vicious cycle that amplifies oxidative impairment. The term antioxidant refers to a compound that is able to impede or retard oxidation, acting at a lower concentration compared to that of the protected substrate. Antioxidant intervention against the radicalic lipid peroxidation can involve different mechanisms. Chain breaking antioxidants are called primary antioxidants, acting by scavenging radical species, converting them into more stable radicals or non-radical species. Secondary antioxidants quench singlet oxygen, decompose peroxides, chelate prooxidative metal ions, inhibit oxidative enzymes. Moreover, four reactivity-based lines of defense have been identified: preventative antioxidants, radical scavengers, repair antioxidants, and those relying on adaptation mechanisms. The specific mechanism of a series of endogenous and exogenous antioxidants in particular aspects of oxidative stress, is detailed. The final section resumes critical conclusions regarding antioxidant supplementation.

Singlet oxygen formation in Na[sbnd]O2 battery cathodes catalyzed by ammonium Brönsted acid

The presence of singlet oxygen in metal-O2 batteries is one of the major factors responsible for the degradation of the electrolyte. The formation of singlet oxygen, 1O2, at NaO2 cathodes in sodium trifluoromethane sulfonate (NaOTf)-diglyme electrolyte has been detected in-operando by fluorescence quenching of 9,10-dimethylanthracene, DMA, a specific chemical monitor of singlet oxygen. Furthermore, ammonium Brönsted acid protonates superoxide and the further disproportionation of HO2 results in a catalytic EC' mechanism that recycles oxygen, a fraction of which has been found to be 1O2. Unlike, ammonium trifluoromethane sulfonate (NH4OTf), in tetrabutylammonium trifluoromethane sulfonate (TBAOTf), which lacks acidic protons, superoxide is stabilized by the large cation and no 1O2 could be detected. The addition of sodium azide to the electrolyte, an efficient specific physical quencher of singlet oxygen, results in negligible detection of this harmful oxygen reduction intermediate and proves the nature of 1O2.

Antioxidant Activity in Supramolecular Carotenoid Complexes Favored by Nonpolar Environment and Disfavored by Hydrogen Bonding.

Carotenoids are well-known antioxidants. They have the ability to quench singlet oxygen and scavenge toxic free radicals preventing or reducing damage to living cells. We have found that carotenoids exhibit scavenging ability towards free radicals that increases nearly exponentially with increasing the carotenoid oxidation potential. With the oxidation potential being an important parameter in predicting antioxidant activity, we focus here on the different factors affecting it. This paper examines how the chain length and donor/acceptor substituents of carotenoids affect their oxidation potentials but, most importantly, presents the recent progress on the effect of polarity of the environment and orientation of the carotenoids on the oxidation potential in supramolecular complexes. The oxidation potential of a carotenoid in a nonpolar environment was found to be higher than in a polar environment. Moreover, in order to increase the photostability of the carotenoids in supramolecular complexes, a nonpolar environment is desired and the formation of hydrogen bonds should be avoided.

A Photoprotective Effect by Cation-π-Interaction? Quenching of Singlet Oxygen by an Indole Cation-π Model System.

We investigated the effect of the cation-π interaction on the susceptibility of a tryptophan model system toward interaction with singlet oxygen, that is, type II photooxidation. The model system consists of two indole units linked to a lariat crown ether to measure the total rate of removal of singlet oxygen by the indole units in the presence of sodium cations (i.e. indole units subject to a cation-π interaction) and in the absence of this interaction. We found that the cation-π interaction significantly decreases the total rate of removal of singlet oxygen (kT ) for the model system, that is, (kT =2.4±0.2)×108 m-1 s-1 without sodium cation vs (kT =6.9±0.9)×107 m-1 s-1 upon complexation of sodium cation to the crown ether. Furthermore, we found that the indole moieties undergo type I photooxidation processes with triplet excited methylene blue; this effect is also inhibited by the cation-π interaction. The chemical rate of reaction of the indole groups with singlet oxygen is also slower upon complexation of sodium cation in our model system, although we were unable to obtain an exact ratio due to differences of the chemical reaction rates of the two indole moieties.

Phytofluene as a Highly Efficient UVA Photosensitizer of Singlet Oxygen Generation.

Phytoene and phytofluene - uncolored C40 carotenoids with short chain of conjugated double bonds (3 and 5, respectively) - are known to be universal precursors in biosynthesis of colored carotenoids in photosynthesizing organisms. It is commonly recognized that C40 carotenoids are photoprotectors of cells and tissues. We have shown that phytofluene is an exception to this rule. By measuring photosensitized phosphorescence of singlet oxygen (1O2) we found out that phytofluene was very effective photosensitizer of 1O2 formation in aerated solutions under UVA irradiation (quantum yield of 85 ± 5%), whereas phytoene was almost inactive in this process. It was demonstrated that both carotenoids quench singlet oxygen in the dark. The obtained quenching rate constants [(4 ± 1) × 106M-1·s-1 for phytoene and (2 ± 0.5) × 107M-1·s-1 for phytofluene] were smaller than the rate constant of the diffusion-controlled reactions by 3-4 orders of magnitude. Thus, both carotenoids displayed rather weak protector properties. Moreover, phytofluene due to its high photosensitizing activity might be considered as a promoter of cell photodamage and a promising UVA photosensitizer for medical purposes.

Evaluation of Phytochemicals and Antioxidant potential of aqueous extract of Myristica fragrans

Antioxidants are substances that can prevent or slow damage to cells caused by free radicals, unstable molecules that the body produces as a reaction to environmental and other pressures. Antioxidants act as radical scavenger, hydrogen donor, electron donor, peroxide decomposer, singlet oxygen quencher, enzyme inhibitor, synergist, and metal-chelating agents. The damage caused by antioxidants has been linked to cancer, atherosclerosis, and vision loss. Need of antioxidant with less side effects emerges nowadays. In this present qualitative evaluation shows this plant contains secondary metabolites like terpenoids, flavanoids, saponins, tannins, alkaloid, steroid, glycosides, proteins and coumarins. Myristica fragrans have been reported for its versatile antioxidant activity.

Quenching of Singlet Oxygen by Carotenoids via Ultrafast Superexchange Dynamics.

We analyze the quenching mechanism of singlet molecular oxygen (1O2) by carotenoids, namely lycopene, β-carotene, astaxanthin, and lutein, by means of quantum dynamics calculations and ab initio calculations. The singlet carotenoid (1Car) and 1O2 molecules can form a weakly bound complex via donation of electron density from the highest occupied molecular orbital (HOMO) of the carotenoid to the πg* orbitals of 1O2. The Dexter-type superexchange via charge transfer states (Car•+/O2•-) governs the 1O2 quenching. The Car•+/O2•- states are substantially higher in energy (2-4 eV) than the initial 1Car/1O2 states. The quantum dynamics calculations indicate an ultrafast 1O2 quenching on a timescale of subpicosecond owing to the strong electronic couplings in the carotenoid/O2 complexes. The superexchange mechanism via the Car•+/O2•- states dominates the 1O2 quenching, although the direct two-electron coupling can also play a certain role.

Furanyl chalcone derivatives as efficient singlet oxygen quenchers. An experimental and DFT/MRCI study

This study reports the antioxidant activity against singlet oxygen (1O2) of five newly synthesized furanyl chalcones (FCs) (E)-3-(5-(4-chlorophenyl)furan-2-yl)-1-arylprop-2-en-1-ones (3a-e). Their structural difference is based on the aryl substituent as follows (Ar): 3a = –C6H4–OCH3, 3b = –C6H3-(1,2-OCH3), 3c = –C6H4OC6H4, 3d = –C10H6-(OCH3) and 3e = –C4H3O. We used a Claisen-Schmidt condensation involving a 5-(4-chlorophenyl)furan-2-carbaldehyde and the corresponding ketones under ultrasonic irradiation. Their property to 1O2 quenching was analyzed in terms of the rate constant for the process (kQ at 25 °C) determined by the Stern–Volmer model in ethanol. For the compounds 3c, 3d and 3e, the kQ values are slightly larger respect to 3a and 3b. The FCs 3c behaves as the best quencher (kQ of 8.44 (±0.09) x 107 M−1s−1). Geometry analysis and electronic structure calculations have been performed in the framework of Density Functional Theory (DFT) and DFT/Multi-Reference Configuration Interaction (DFT/MRCI) methods. According to DFT/MRCI, a physical quenching of 1O2 from the ground states of the FCs may not likely induce a spontaneous energy transfer processes but a chemical quenching mechanism may dominate the kinetics.

Sonodynamically-induced Anticancer Effects of Polyethylene Glycol-Modified Carbon Nano Tubes

Sonodynamic cancer therapy is based on the preferential uptake and/or retention of a sonosensitizing drug (sonosensitizer) in tumor tissues and the subsequent activation of the drug by ultrasound irradiation. In the present study, we investigated the sonodynamically-induced antitumoral effect with functionalized carbon nanotubes, such as poly-ethylene glycol-modified carbon nanotubes (PEG-modified CNTs). Antitumor effects were evaluated using histological observation and assessing tumor growth following sonodynamic exposure to PEG-modified CNTs. The combined treatment of 100 μM PEG-modified CNT and ultrasound induced a 2-fold cytotoxicity. Sodium azide, which quenches singlet oxygen, significantly inhibited ultrasonication induced cell damage in the presence of PEG-modified CNTs. This suggests that singlet oxygen produced by the combined use of PEG-modified CNTs and ultrasound is involved in the induction of antitumoral effects. The destruction of tumor tissue was observed with the ultrasonic treatment in combination with PEG-modified CNTs, while neither the treatment with PEG-modified CNTs alone nor ultrasound alone caused any necrosis. These results indicate that PEG-modified CNT functions as a sonosensitizer and is effective for sonochemical treatment of solid tumors.

Nutraceutical characteristics of the brown seaweed carotenoid fucoxanthin

Fucoxanthin (Fx), a major carotenoid found in brown seaweed, is known to show a unique and wide variety of biological activities. Upon absorption, Fx is metabolized to fucoxanthinol and amarouciaxanthin, and these metabolites mainly accumulate in visceral white adipose tissue (WAT). As seen in other carotenoids, Fx can quench singlet oxygen and scavenge a wide range of free radicals. The antioxidant activity is related to the neuroprotective, photoprotective, and hepatoprotective effects of Fx. Fx is also reported to show anti-cancer activity through the regulation of several biomolecules and signaling pathways that are involved in either cell cycle arrest, apoptosis, or metastasis suppression. Among the biological activities of Fx, anti-obesity is the most well-studied and most promising effect. This effect is primarily based on the upregulation of thermogenesis by uncoupling protein 1 expression and the increase in the metabolic rate induced by mitochondrial activation. In addition, Fx shows anti-diabetic effects by improving insulin resistance and promoting glucose utilization in skeletal muscle.

Synthesis, Characterization, Photophysical and Photochemical Properties of Novel Phthalocyanines

AbstractThe benzothiazole substituted phthalonitrile (3) and non‐peripherally tetra benzothiazole substituted metal‐free (4), zinc(II) (5) and lead(II) phthalocyanine (6) complexes were prepared. The compounds (3‐6) were characterized by IR, NMR, UV‐Vis and mass spectroscopy data. After synthesis, photochemical and photophysical parameters of the compounds (4‐6) were analyzed to determine photosensitizer performance of them for PDT applications. Firstly, the most suitable solvent for compounds (4‐6) was found by aggregation studies. Then, fluorescence properties were measured in DMF at 1x10−6 M. Singlet oxygen properties were measured in DMF by using 1,3‐diphenylisobenzofuran (DPBF) as a singlet oxygen quencher. Photodegradation properties were measured under light irradiation in DMF at 1x10−5 M. The zinc(II) phthalocyanine (5) had the highest singlet oxygen production capacity (Φ▵=0.62), fluorescence (ΦF=0.25) and photodegradation quantum yield (Φd=3.28x10‐4). The results showed that zinc(II) phthalocyanine (5) has potential for photodynamic therapy applications.