Singlet Oxygen Scavenger Research Articles

Quantitative analysis of oxidized vitamin B1 metabolites generated by hypochlorous acid

Thiamine, a water-soluble essential vitamin known as vitamin B1, acts as an important cofactor in various cellular processes, such as metabolism and energy production. Thiamine is also thought to have antioxidant effects as a singlet oxygen scavenger and a lipid peroxidation inhibitor. However, the oxidation mechanism and oxidized metabolites of thiamine are not completely established. In the present study, we investigated the oxidative reactivity of thiamine and found that three products were formed upon the reaction of thiamine with hypochlorous acid (HOCl). Based on the NMR and high resolution mass spectrometric analysis, the HOCl-oxidized metabolites of thiamine were identified as formylaminopyrimidine (FAP), thiamine sulfonic acid (TSA), and thiamine sulfinic ester (TSE). To evaluate the formation of these oxidized metabolites in vivo, we established a specific method for quantification of the oxidized thiamine metabolites using liquid chromatography-tandem mass spectrometry coupled with a stable isotope dilution method. Using this method, it was shown that the oxidized thiamine metabolites were generated in the culture media of phorbol-12-myristate-acetate-treated neutrophil-like cells in a myeloperoxidase-dependent manner. Moreover, significantly higher amounts of FAP and TSE were detected in the lung tissues of the lipopolysaccharide-treated mice compared to the controls. These findings provide not only insights into the oxidative metabolism of thiamine, but also the possibility that the oxidized thiamine metabolites may be potential biomarkers for HOCl-related oxidative stress.

Photoinactivation of Salmonella enterica (serovar Typhimurium) by tetra-cationic porphyrins containing peripheral [Ru(bpy)2Cl]+ units

In the last years, antimicrobial photodynamic therapy (aPDT) has been considered as one important alternative to be used in antimicrobial treatments. In the present work we report the first photoinactivation of Salmonella enterica serovar Typhimurium (Salmonella Typhimurium) by cationic free-base meso-tetra-(phenyl)porphyrin and its Zn(II) complex containing peripheral Ru(II)-bipyridyl complexes. Bacterial inoculum (107 CFU mL-1) was incubated with the porphyrins (25 μM) with an irradiation system containing a halogen lamp with fluence values of 0, 180, 360, 720 and 1080 J cm-2. Both porphyrins demonstrate phototoxicity against bacteria, but higher efficiency was observed by Zn(II) complex. It was demonstrated that RuTPyP and ZnRuTPyP phototoxicity is due to their photodynamic activity associated with the formation of singlet oxygen, anion superoxide and hydroxyl radical at their irradiation by visible light. The formation of these reactive species was confirmed using flash-photolysis technique and spin-trap electron paramagnetic resonance (EPR) spectroscopy. The singlet oxygen quantum yield was determined by indirect method using the uric acid as singlet oxygen scavenger. Besides the characterization of optical absorption and fluorescence RuTPyP and ZnRuTPyP properties were realized using optical absorption and fluorescence spectroscopies. It was observed that complexation with Zn(II) ion increases the quantum yields of porphyrin fluorescence and singlet oxygen formation.

Mechanism behind the degradation of aqueous norbixin upon storage in light and dark environment

Buffered aqueous solutions of norbixin were stored in light and dark, and analyzed using mass spectrometry. Compounds with both higher and lower masses than norbixin were detected, suggesting the formation of oxidation products and oxidative cleavage products of norbixin. The norbixin oxidation products included compounds containing several oxidations. The amounts of oxidation products of norbixin increased during storage in both light and dark, but in light, the development accelerated. Scavengers of superoxide radical anion (superoxide dismutase), hydrogen peroxide (catalase), hydroxyl radicals (mannitol) and singlet oxygen (sodium azide) and carbon-centered radicals (DMPO) were tested to determine if any of the reactive species were involved in the degradation of norbixin. Of these, only DMPO decreased the bleaching of norbixin indicating the involvement of carbon-centered radicals. Multiple oxidations of norbixin might be a result of a radical chain reaction involving peroxyl and carbon-centered radicals even though not detectable with electron spin resonance.

Lycopene prevents the progression of lipotoxicity-induced nonalcoholic steatohepatitis by decreasing oxidative stress in mice

Excessive fatty acid uptake-induced oxidative stress causes liver injury and the consecutive recruitment of inflammatory immune cells, thereby promoting the progression of simple steatosis to nonalcoholic steatohepatitis (NASH). Lycopene, the most effective singlet oxygen scavenger of the antioxidant carotenoids, has anti-inflammatory activity. Here, we investigated the preventive and therapeutic effects of lycopene in a lipotoxic model of NASH: mice fed a high-cholesterol and high-fat diet. Lycopene alleviated excessive hepatic lipid accumulation and enhanced lipolysis, decreased the proportion of M1-type macrophages/Kupffer cells, and activated stellate cells to improve hepatic inflammation and fibrosis, and subsequently reduced the recruitment of CD4+ and CD8+ T cells in the liver. Importantly, lycopene reversed insulin resistance, as well as hepatic inflammation and fibrosis, in pre-existing NASH. In parallel, lycopene decreased LPS-/IFN-γ-/TNFα-induced M1 marker mRNA levels in peritoneal macrophages, as well as TGF-β1-induced expression of fibrogenic genes in a stellate cell line, in a dose-dependent manner. These results were associated with decreased oxidative stress in cells, which might be mediated by the expression of NADPH oxidase subunits. In summary, lycopene prevented and reversed lipotoxicity-induced inflammation and fibrosis in NASH mice by reducing oxidative stress. Therefore, it might be a novel and promising treatment for NASH.

Selenomethionine induces oxidative stress and modifies growth in rice (Oryza sativa L.) seedlings through effects on hormone biosynthesis and primary metabolism.

Although the chemical characteristics of selenomethionine (SeMet) are similar to those of methionine (Met), the physiological activity of SeMet apparently differs in its ability to stimulate ethylene production in plant tissues. Since selenium alters root architecture of rice seedlings by modifying ethylene production, the investigation of the effect of SeMet and Met on rice growth would be a step forward towards unraveling factors that underlie selenium toxicity. Here, we report that SeMet increased concentrations of reactive oxygen species (ROS), inhibiting auxin and increasing ethylene production in rice seedlings. The effect of SeMet on seedlings was mediated by the inhibition of the abundance of transcripts encoding auxin transport and cell expansion proteins. Moreover, SeMet led to increased seedling respiration, which was positively correlated with organic acids consumption, but negatively with sugars consumption, thereby decreasing seedling growth. In contrast with SeMet treatment, Met did not affect ROS production, hormone biosynthesis and seedling growth, indicating an exclusive selenium effect. The singlet oxygen scavenger, 1,4-diazabicyclooctane, overrode the repressive effect of SeMet in seedling growth. Our results demonstrate a phytotoxic effect of SeMet for rice seedlings and reveal a relationship between reactive oxygen species, hormone homeostasis and carbon availability, which regulates growth responses.

Evaluation of Singlet Oxygen Scavenging Capacity of Peppermint (Mentha Piperita L.), Marjoram (Origanum Majorana L.), Rosemary (Rosmarinus Officinalis L.) And Sage (Salvia Officinalis L.) on Fatty Acid Photooxidation

Lipid photooxidation is the undesirable chemical process in which singlet oxygen result in the peroxidation of fatty acids. In this study leaves methanolic extracts of peppermint (Mentha piperita L.), marjoram (Origanum majorana L.), rosemary (Rosmarinus officinalis L.) and sage (Salvia officinalis L.) were applied as the natural singlet oxygen scavenger. Amount of flavonoid compounds as the singlet oxygen scavenger agent in these plant species were decreased in the order of peppermint > marjoram> sage > rosemary. Also, The rate of quenching of singlet oxygen in the presence of 1,4-Diazabicyclo[2.2.2]octane (DABCO) as a well-known singlet oxygen scavenger and highly effective synthetic antioxidants in food industry such as Butylated hydroxyanisole (BHA), tert-Butylhydroquinone (TBHQ) and peppermint decreased in the order of peppermint > BHA > TBHQ > DABCO >. Furthermore, photooxidation of oleic acid as an unsaturated fatty acid in the presence of DABCO, peppermint, BHA and TBHQ indicated a preservation of 82.77%, 73.39%, 71.57% and 53.10% on peroxidation of oleic acid, respectively which reveals peppermint has an efficient role on protection of fatty acids from photooxidation. Practical application: In this study, it was confirmed that peppermint (Mentha piperita L.) performs an effective role in restricting or limitation of singlet oxygen generation and fatty acid photooxidation. In vitro study of scavenging effect of peppermint can correlate laboratory results to commercial scale up. However, this would also necessitate the progress of improved methods for the measurement of lipid peroxidation in vivo in the presence of peppermint.

Acceleration effect of the forensic luminol reaction induced by visible light irradiation of whole human blood aqueous solutions

The first quantitative study on the effect of visible light irradiation on the luminol reaction, used forensically, was conducted using whole human blood aqueous solutions (hemolytic state) and an LED lamp. Whole human blood aqueous solutions under an air atmosphere were irradiated with visible light, resulting in the maximum chemiluminescence (CL) intensity (@ 440 nm) increasing about 1.7-fold due to acceleration of the luminol reaction rate. No acceleration effect was observed under an argon (Ar) atmosphere, or under an air atmosphere in the presence of sodium azide (NaN3; a scavenger of singlet oxygen (1O2)). Furthermore, no conversion from Fe(II) hemoglobin to Fe(III) hemoglobin (methemoglobin) was observed in the absorption spectrum following irradiation. We suggest that these effects are due to easier approach of the luminol reagents to heme following damage of the globin protein around the heme, or damage to the red blood cell membrane, induced by 1O2 generated by an excited state of heme.

Apoptosis Induced by Ultraviolet A Exposure in the Presence of Enoxacin in HL-60 Cells.

The ultraviolet A (UVA) spectrum mainly includes the region associated with the phototoxicity of fluoroquinolone antimicrobial agents. This study investigated apoptosis induced with UVA light and enoxacin in HL-60 cells. HL-60 cells were irradiated by UVA (1.1 mW/cm2) for 20 min in the presence or absence of enoxacin. The induction of apoptosis was investigated by analysing cell morphology, flow cytometry of annexin V-positive cells, DNA ladder formation, and caspase-3 activation. Significant induction of apoptosis, DNA fragmentation, and caspase-3 activation were observed in cells treated with both UVA and enoxacin. UVA-induced apoptosis was significantly suppressed when NaN3, a singlet oxygen scavenger, was present. Apoptosis was induced by the combination of UVA and enoxacin in HL-60 cells, and singlet oxygen appears to play an important role in photodynamically-induced apoptosis.

The intracellular redox environment modulates the cytotoxic efficacy of single and combination chemotherapy in breast cancer cells using photochemical internalisation.

Background: Photochemical internalisation (PCI) is a light-triggered and site-specific technique that enhances the delivery of therapeutic agents to their intracellular targets using amphiphilic, photosensitizing agents. Methods: This study investigated the effect that the intracellular redox environment of 4T1 breast cancer cells exerts on PCI-facilitated delivery of the type I ribosome inactivating protein, saporin, and the topoisomerase inhibitor, mitoxantrone, either individually or in combination. Buthionine sulfoximime (BSO), a clinically used inhibitor of glutathione synthesis, and the singlet oxygen scavenger, l-histidine, were used to enhance the oxidative and reductive state of the cells respectively. Results: PCI of saporin at 30 nM was effective in reducing cellular viability, which decreased to 16% compared to “dark” controls (P < 0.01). Addition of BSO enhanced PCI efficacy by a further factor of three (P < 0.01), but addition of l-histidine completely inhibited cytotoxicity induced by PCI. The combination of the two cytotoxic agents, saporin and mitoxantrone, with PCI, elicited 14% and 17% reduction in cell viability (P < 0.01) compared to PCI with saporin alone and mitoxantrone alone respectively. Combination treatment with BSO resulted in a further significant reduction in cell viability by 18% (P < 0.01). Conclusions: Our findings show the efficacy of PCI can be manipulated and potentiated by modifying the intracellular redox environment.

Suppressing Effect of 2-Nitrobenzaldehyde on Singlet Oxygen Generation, Fatty Acid Photooxidation, and Dye-Sensitizer Degradation.

2-Nitrobenzaldehyde was found to efficiently block singlet oxygen generation in a series of different test samples upon exposure to UV and visible light under aerobic conditions. The effect of quenching singlet oxygen formation was monitored in the presence of 1, 4-diazabicyclo [2.2.2] octane (DABCO) acting as a well-known singlet oxygen scavenger. A comparison of different nitrobenzaldehyde isomers with other highly effective synthetic antioxidants used in the food industry such as butylated hydroxytoluene (BHT), butylated hydroxyanisole (BHA), tert-butylhydroquinone (TBHQ) revealed that the protection of materials from singlet oxygen decreases in the order of 2-nitrobenzaldehyde > DABCO > TBHQ > 3-nitrobenzaldehyde > BHA > 4-nitrobenzaldehyde > BHT. Upon addition of 2-nitrobenzaldehyde, the oxidation of fatty acids and the degradation of photosensitizers was found to be considerably diminished, which indicates that the presence of 2-nitrobenzaldehyde has a significant protective influence by restricting the singlet oxygen generation and photodegradation of dyes. Moreover, the compound turned out to display its highly suppressing effects on typical singlet oxygen-dependent reactions, such as fatty acid photooxidation and dye photosensitizer degradation, in a rather broad spectral region covering wavelengths from 300 nm (UV-B) to 575 nm (close to the maximum of ambient solar radiation).

Effect of Different Cooking Methods on Polyphenols, Carotenoids and Antioxidant Activities of Selected Edible Leaves.

This study aimed to evaluate the effect of cooking (boiling, steaming, and frying) on polyphenols, flavonoids, carotenoids and antioxidant activity of six edible leaves. The total antioxidant capacity of the fresh and cooked leaves was determined using 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and singlet oxygen scavenging assays. The results revealed that frying caused a reduction in major bioactives and antioxidant activities in all leafy vegetables tested. However, steamed and boiled leaves of C. auriculata and C. asiatica have shown greater levels of polyphenols, flavonoids, and antioxidant capacity compared with fresh leaves. Polyphenol and flavonoid contents of boiled S. grandiflora and G. lactiferum were higher than that of their fresh form. Boiled and steamed O. zeylanica and S. grandiflora have shown higher carotenoids. Boiled and steamed leaves of P. edulis have shown higher antioxidant activity. The impact of cooking on the changes in bioactive concentrations and antioxidant capacities are dependent on the species and the method of cooking.

Triplet Excited Carbonyls and Singlet Oxygen Formation During Oxidative Radical Reaction in Skin.

The skin is the largest organ in the body and is consistently exposed to aggressive environmental attacks (biological/physical/chemical, etc.). Reactive oxygen species (ROS) are formed during the normal oxidative metabolism which enhances to a lethal level under stress conditions referred to as oxidative stress. While, under normal conditions, cells are capable of dealing with ROS using non-enzymatic and enzymatic defense system, it can lead to a critical damage to cell system via the oxidation of cellular components under stress condition. Lipid peroxidation is a well-established mechanism of cellular injury in all kinds of organisms and it is often used as an indicator of oxidative stress in cells and tissues. In the presence of metal ions, ROS such as hydrogen peroxide (H2O2) produces highly reactive hydroxyl radical (HO•) via Fenton reaction. In the current study, we have used the porcine skin (intact pig ear/skin biopsies) as an ex vivo/in vitro model system to represent human skin. Experimental results have been presented on the participation of HO• in the initiation of lipid peroxidation and thereby leading to the formation of reactive intermediates and the formation of electronically excited species eventually leading to ultra-weak photon emission (UPE). To understand the participation of different electronically excited species in the overall UPE, the effect of a scavenger of singlet oxygen (1O2) on photon emission in the visible and near-infrared region of the spectrum was measured which showed its contribution. In addition, measurement with interference filter with a transmission in the range of 340–540 nm reflected a substantial contribution of triplet carbonyls (3L=O∗) in the photon emission. Thus, it is concluded that during the oxidative radical reactions, the UPE is contributed by the formation of both 3L=O∗ and 1O2. The method used in the current study is claimed to be a potential tool for non-invasive determination of the physiological and pathological state of human skin in dermatological research.

Analysis of rutin, β‐carotene, and lutein content and evaluation of antioxidant activities of six edible leaves on free radicals and reactive oxygen species

The antioxidant potency of soluble and bound phenolic extracts of freeze-dried six leafy vegetables was investigated using in vitro systems; singlet oxygen scavenging, hydroxyl radical scavenging, nitric oxide radical scavenging, and ABTS radicals assays. Further rutin, lutein, and β-carotene content of leaves were analysed. The results revealed that both soluble and bound phenolic extracts have exhibited antioxidant potential toward free radicals and reactive oxygen species concerned. However, soluble extracts showed a higher content of phenolics and flavonoids than the bound counterpart. The highest rutin, lutein, and β-carotene contents were observed in the leaves of Cassia auriculata, and the leaves of Passiflora edulis showed the highest vitamin C content. Positive associations between phenolics and antioxidant activities except for singlet oxygen radical scavenging ability were observed. Among the leafy types studied, C. auriculata have shown to possess more antioxidant bioactives such as β-carotene, lutein, and rutin and antioxidant activities. Practical applications This paper will give information about major bioactive compounds such as β-carotenoids, rutin, and lutein and antioxidant activity in selected green leafy vegetables due to cooking treatments. This is important for the public those concern about the healthy diet in the view of selecting leafy vegetables to combat many oxidative stress-related chronic diseases.

Scavenging effect of pasipay (passiflora incarnate L.) on singlet oxygen generation and fatty acid photooxygenation.

Anthracene as a chemical probe is usually used to trap the singlet oxygen and then detection and quantification can be based on absorbance. In this study, oxidation of anthracene declared that rate of singlet oxygen quenching in the presence of pasipay (passiflora incarnate L.) as a natural antioxidant, 1,4 Diazabicyclo [2.2.2] octane (DABCO) as a well‐known singlet oxygen scavenger and highly effective synthetic antioxidants in food industry such as Butylated hydroxytoluene (BHT), Butylated hydroxyanisole (BHA), tert‐Butylhydroquinone (TBHQ) decreased in the order of DABCO >pasipay > TBHQ > BHT > BHA. On the other hand, lipid photooxidation is the undesirable chemical process in which singlet oxygen result in the peroxidation of fatty acids. The results of this study also showed that oleic acid oxidation with singlet oxygen in the presence of pasipay (contains 0.4576 mg flavonoid compounds) diminished about 11% which shows pasipay has an effective role to inhibit lipid peroxidation.

The plastoquinone pool outside the thylakoid membrane serves in plant photoprotection as a reservoir of singlet oxygen scavengers.

The Arabidopsis vte1 mutant is devoid of tocopherol and plastochromanol (PC-8). When exposed to excess light energy, vte1 produced more singlet oxygen (1 O2 ) and suffered from extensive oxidative damage compared with the wild type. Here, we show that overexpressing the solanesyl diphosphate synthase 1 (SPS1) gene in vte1 induced a marked accumulation of total plastoquinone (PQ-9) and rendered the vte1 SPS1oex plants tolerant to photooxidative stress, indicating that PQ-9 can replace tocopherol and PC-8 in photoprotection. High total PQ-9 levels were associated with a noticeable decrease in 1 O2 production and higher levels of Hydroxyplastoquinone (PQ-C), a 1 O2 -specific PQ-9 oxidation product. The extra PQ-9 molecules in the vte1 SPS1oex plants were stored in the plastoglobules and the chloroplast envelopes, rather than in the thylakoid membranes, whereas PQ-C was found almost exclusively in the thylakoid membranes. Upon exposure of wild-type plants to high light, the thylakoid PQ-9 pool decreased, whereas the extrathylakoid pool remained unchanged. In vte1 and vte1 SPS1oex plants, the PQ-9 losses in high light were strongly amplified, affecting also the extrathylakoid pool, and PQ-C was found in high amounts in the thylakoids. We conclude that the thylakoid PQ-9 pool acts as a 1 O2 scavenger and is replenished from the extrathylakoid stock.

Singlet Oxygen Plays an Essential Role in the Root's Response to Osmotic Stress.

The high osmotic potentials in plants subjected to drought stress can be mimicked by the application of high molecular weight polyethylene glycol. Here, we quantified the effects of exposure to polyethylene glycol on the growth of the main and lateral roots of Arabidopsis (Arabidopsis thaliana) seedlings. The effects on root growth were highly correlated with the appearance of singlet oxygen, as visualized using the singlet oxygen-specific probe singlet oxygen sensor green. The production of singlet oxygen was followed by cell death, as indicated by the intracellular accumulation of propidium iodide due to the loss of membrane integrity. Cell death began in the epidermal region of the root tip and spread in a dynamic manner to meristematic sections. In parallel, gene expression changes specific to the presence of singlet oxygen were observed. The accumulation of other reactive oxygen species, namely hydrogen, peroxide, nitric oxide, and superoxide, did not correlate with cell death. In addition, both the singlet oxygen scavenger His and the lipoxygenase inhibitor salicylhydroxamic acid specifically inhibited singlet oxygen accumulation and cell death. These results suggest a light-independent, type-I source of singlet oxygen production. Serpin-protease interactions were used as a model to assess the possibility of vacuolar-type cell death. Osmotic stress induced the accumulation of complexes between the cytoplasmic serpin AtSERPIN1 and its cognate vacuolar proteases, indicating that vacuolar integrity was compromised. These findings imply that singlet oxygen plays an essential role in conveying the root response to osmotic stress.

Bandgap Tunable AgInS based Quantum Dots for High Contrast Cell Imaging with Enhanced Photodynamic and Antifungal Applications

Herein, we report a facile microwave-assisted synthesis of cadmium-free water-soluble silver indium sulfide (AgInS2 or AIS) and AgInS@ZnS (or AIS@ZnS) core-shell quantum dots (QDs) using glutathione (GSH) as stabilizer. The core and core-shell nanocrystals exhibit tunable bandgap ranging of 2.3–3.1 and 2.4–3.5 eV, mean particle size of 2.5 and 3.25 nm, quantum yield of 26% and 49%, and fluorescence lifetimes of 326 and 438 ns, respectively. The core-shell QDs exhibit color-tunable emission in the visible region (500 to 600 nm), where the tunability was achieved by varying the molar ratio of Ag:In in the precursors. In vitro evaluation of antifungal activity of these water/ buffer stable QDs against the fungal pathogen, Candida albicans demonstrated that these were not toxic to the fungal cells upto a concentration of 100 µg/ml for 16 hours of incubation. Confocal imaging and spectrofluorometric studies showed enhanced fluorescence inside the microbial cells suggesting that AIS@ZnS particles had the capability to easily penetrate the cells. The increased generation of reactive oxygen species was evaluated for the core-shell QDs (photosensitizers) by using 9, 10-anthracenediyl-bis(methylene)dimalonic acid (ABMDMA) as singlet oxygen (1O2) scavenger molecule. These QDs have the potential for use as high contrast cell imaging, photodynamic and antifungal agents.

Photo-induced antibacterial activity of a porphyrin derivative isolated from the harmful dinoflagellate Heterocapsa circularisquama

The dinoflagellate Heterocapsa circularisquama is highly toxic to bivalves. However, significant toxicity to finfish species has not been reported. We previously found that H. circularisquama has light-dependent haemolytic agents. Purification and chemical structural analyses revealed that the haemolytic agent H2-a is a porphyrin derivative, which exhibits light-dependent cytotoxicity toward tumour cells. To clarify the biological activity of H2-a further, its antibacterial activities against Gram-positive and Gram-negative bacteria were investigated in this study. A fraction (F5) equivalent to H2-a purified from the methanol extract of H. circularisquama showed potent light-dependent bactericidal activity toward Staphylococcus aureus, and the activity was concentration- and light illumination time-dependent; however, Escherichia coli was highly resistant to F5. Electron microscopic observation suggested that F5 induces morphological changes in S. aureus in a light-dependent manner. Further analysis using other bacterial species showed that the Gram-positive bacterium Bacillus subtilis was more sensitive than the Gram-negative bacteria Pseudomonas aeruginosa and Vibrio alginolyticus. These results indicate that F5 is a photo-induced antibacterial agent with relatively higher specificity to Gram-positive bacteria. Iodometric assay suggested that singlet oxygen was generated from light-illuminated F5. Histidine, a specific singlet oxygen scavenger, markedly inhibited the photosensitising antibacterial activity of F5 against S. aureus, suggesting the involvement of singlet oxygen in antibacterial activity. The antibacterial spectrum of F5 was evidently different from that of 5,10,15,20-tetra (N,N,N-trimethylanilinium) porphyrin tetratosylate, a commercially available porphyrin compound with antibacterial activity. Our results demonstrate that H. circularisquama has a novel antibacterial photosensitiser, a porphyrin derivative, with relatively higher specificity to Gram-positive bacteria. To the best of our knowledge, this is the first study to discover a porphyrin derivative with antibacterial activity in marine microalga.

Cold atmospheric-pressure plasma induces DNA–protein crosslinks through protein oxidation

Reactive oxygen and nitrogen species (ROS and RNS) generated by cold atmospheric-pressure plasma could damage genomic DNA, although the precise types of these DNA damage induced by plasma are poorly characterized. Understanding plasma-induced DNA damage will help to elucidate the biological effect of plasma and guide the application of plasma in ROS-based therapy. In this study, it was shown that ROS and RNS generated by physical plasma could efficiently induce DNA-protein crosslinks (DPCs) in bacteria, yeast, and human cells. An in vitro assay showed that plasma treatment resulted in the formation of covalent DPCs by activating proteins to crosslink with DNA. Mass spectrometry and hydroperoxide analysis detected oxidation products induced by plasma. DPC formation were alleviated by singlet oxygen scavenger, demonstrating the importance of singlet oxygen in this process. These results suggested the roles of DPC formation in DNA damage induced by plasma, which could improve the understanding of the biological effect of plasma and help to develop a new strategy in plasma-based therapy including infection and cancer therapy.

P-103 - The activity of proline as singlet oxygen and superoxide scavenger

Proline (Pro) is an important stress protecting molecule in plants and other cellular systems against oxidative damage. However, the actual sensitivity and selectivity of Pro against specific reactive oxygen species (ROS), especially singlet oxygen and superoxide, is debated. Here we present in vitro studies by using EPR and oxygen uptake detection of ROS showing that Pro can indeed scavenge both singlet oxygen and superoxide. The scavenging activity of Pro is compared to that of ascorbate (Asc), a known quencher of singlet oxygen and superoxide. In contrast to Asc, which a chemical quencher, Pro eliminates singlet oxygen via a physical mechanism with ca. 1% efficiency that of Asc. The superoxide scavenging activity of Pro does not proceed via H2O2 production as in case of superoxide dismutase (SOD), but similar to that of Asc that includes electron transfer, and its efficiency is ca. 6% that of Asc on equal molar basis. Since Pro can accumulate up to 10-fold higher concentrations under stress conditions than Asc, the overall singlet oxygen and superoxide elimination activity of Pro can reach 10 and 60% of the activity of Asc, respectively. In stress exposed plants this could be physiologically relevant in cell compartments with low amount of more efficient scavengers.