Galvinoxyl Research Articles

A new insight into the oxidative mechanism of caffeine and related methylxanthines in aprotic medium: May caffeine be really considered as an antioxidant?

BackgroundAntioxidant properties have been recently suggested for caffeine that seems showing protective effects against damages caused by oxidative stress. In particular, a HO scavenging activity has been ascribed to caffeine. Even if the oxidation of caffeine has been widely studied, the antioxidant mechanism is still far to be understood. MethodsThe electrochemical behavior of caffeine, theobromine and theophylline was studied in aprotic medium by cyclic voltammetry and electrolysis in UV–vis cell; a computational analysis of the molecular structures based on the Density Functional Theory was performed; the reactivity of all substrates towards lead dioxide, superoxide and galvinoxyl radical was followed by UV–vis spectrophotometry. ResultsResults supported the mono-electronic oxidation of the C4C5 bond for all substrates at high oxidation potentials, the electron-transfer process leading to a radical cation or a neutral radical according to the starting methylxanthine N7-substituted (caffeine and theobromine) or N7-unsubstituted (theophylline), respectively. A different following chemical fate might be predicted for the radical cation or the neutral radical. No interaction was evidenced towards the tested reactive oxygen species. ConclusionsNo reactivity via H-atom transfer was evidenced for all studied compounds, suggesting that an antiradical activity should be excluded. Some reactivity only with strong oxidants could be predicted via electron-transfer. The acclaimed HO scavenging activity should be interpreted in these terms. The study suggested that CAF might be hardly considered an antioxidant. General significanceBeyond the experimental methods used, the discussion of the present results might provide food for thought to the wide audience working on antioxidants.

Rosemary (Rosmarinus officinalis) oil: composition and functionality of the cold-pressed extract

The aim of this work was to investigate cold-pressed rosemary oil (RO) for its lipid classes, subclasses, fatty acid composition, tocochromanols and total phenolics amount. Antiradical activity against 1,1-diphenyl-2-picrylhydrazyl (DPPH•) and galvinoxyl radicals, antioxidant activity, as measured by the Rancimat test, as well as antimicrobial activity against food-borne bacteria, and dermatophytic fungi of RO were evaluated. In RO, the amount of neutral lipids was highest (ca. 86%), followed by phospholipids (0.92%) and glycolipids (0.88%). The percentages of monounsaturated, polyunsaturated, and saturated fatty acids were 41.7, 42.3, and 15.8%, respectively. Linoleic acid (41.7%) and oleic acid (41.2%) were the major fatty acids while linolenic acid accounted for 1.3% of total fatty acids. The following tocochromanols were detected: α-, β-, γ- and δ-tocopherols, which accounted for 291, 22, 1145, and 41 mg/100 g oil, respectively, as well as α-, β-, γ- and δ-tocotrienols, which accounted for 18, 12, 29, and 158 mg/100 g oil, respectively. RO also contained high levels of phenolic compounds (7.2 mg GAE/g). After 60 min of reaction with free radicals, 67% of DPPH• and 55% of galvinoxyl radicals were quenched by RO. Rancimat test showed that blending RO with sunflower oil increased the induction period (IP) for blends. The IP of the RO: sunflower oil blend (1:9, v/v) was 390 min, and RO: sunflower oil blend (2:8, v/v) was longer (540 min). RO exhibited high antimicrobial potential against food-borne pathogenic bacteria (E. coli, S. enteritidis, and L. monocytogenes) and high antifungal potential against dermatophyte fungi (T. mentagrophytes, and T. rubrum). RO had unique high level of γ-tocopherol, which is a scavenger of reactive nitrogen species making it a promising material in the food, cosmetic and pharmaceutical applications.

Characterisation of the electronic structure of galvinoxyl free radical by variable energy UPS, XPS and NEXAFS spectroscopy.

Insights into the electronic structure of galvinoxyl - a prototype persistent free radical species - are of interest to elucidate its attractive photophysical and magnetic properties and to pave way for a sensible design of novel applications. To this end, we study the photoionization and photoexcitation UPS, XPS and NEXAFS spectra of the gas-phase galvinoxyl in the valence and core (C 1s and O 1s) regions using synchrotron X-ray radiation. We observe significant variations of relative band intensities with photon energy for valence ionizations below 10 eV which are rationalized in terms of the properties of the corresponding valence molecular orbitals. We calculate the core electron binding energies and core-excited states by employing the spin-unrestricted ΔDFT (B3LYP, M06-2X, and ωB97xD) and time-dependent DFT (SRC2-BLYP) methods. A good correlation between the calculations and the measured C 1s and O 1s XPS and NEXAFS spectra is obtained if one assumes that the galvinoxyl sample has undergone a partial degradation (around 50%) to the saturated (closed-shell) phenolic-quinonic derivative known as galvinol. We carry out a comparative theoretical analysis of the XPS and NEXAFS spectra of galvinoxyl and galvinol by assigning the relevant absorptions and pointing out the most important relative differences. The calculations identify a band in the O 1s NEXAFS spectrum whose diminishing intensity is a most manifest indicator of the extent of the degradation. Such a feature may thus prove useful in monitoring the scavenging dynamics of galvinoxyl using the core-excitation spectroscopy.

Protection by extra virgin olive oil against oxidative stress in vitro and in vivo. Chemical and biological studies on the health benefits due to a major component of the Mediterranean diet.

We report the results of in vivo studies in Caenorhabditis elegans nematodes in which addition of extra virgin olive oil (EVOO) to their diet significantly increased their life span with respect to the control group. Furthermore, when nematodes were exposed to the pesticide paraquat, they started to die after two days, but after the addition of EVOO to their diet, both survival percentage and lifespans of paraquat-exposed nematodes increased. Since paraquat is associated with superoxide radical production, a test for scavenging this radical was performed using cyclovoltammetry and the EVOO efficiently scavenged the superoxide. Thus, a linear correlation (y = -0.0838x +19.73, regression factor = 0.99348) was observed for superoxide presence (y) in the voltaic cell as a function of aliquot (x) additions of EVOO, 10 μL each. The originally generated supoeroxide was approximately halved after 10 aliquots (100 μL total). The superoxide scavenging ability was analyzed, theoretically, using Density Functional Theory for tyrosol and hydroxytyrosol, two components of EVOO and was also confirmed experimentally for the galvinoxyl radical, using Electron Paramagnetic Resonance (EPR) spectroscopy. The galvinoxyl signal disappeared after adding 1 μL of EVOO to the EPR cell in 10 minutes. In addition, EVOO significantly decreased the proliferation of human leukemic THP-1 cells, while it kept the proliferation at about normal levels in rat L6 myoblasts, a non-tumoral skeletal muscle cell line. The protection due to EVOO was also assessed in L6 cells and THP-1 exposed to the radical generator cumene hydroperoxide, in which cell viability was reduced. Also in this case the oxidative stress was ameliorated by EVOO, in line with results obtained with tetrazolium dye reduction assays, cell cycle analysis and reactive oxygen species measurements. We ascribe these beneficial effects to EVOO antioxidant properties and our results are in agreement with a clear health benefit of EVOO use in the Mediterranean diet.

Can Carbamates Undergo Radical Oxidation in the Soil Environment? A Case Study on Carbaryl and Carbofuran.

Radical oxidation of carbamate insecticides, namely carbaryl and carbofuran, was investigated with spectroscopic (electron paramagnetic resonance [EPR] and UV-vis) and theoretical (density functional theory [DFT] and ab initio orbital-optimized spin-component scaled MP2 [OO-SCS-MP2]) methods. The two carbamates were subjected to reaction with •OH, persistent DPPH• and galvinoxyl radical, as well as indigenous radicals of humic acids. The influence of fulvic acids on carbamate oxidation was also tested. The results obtained with EPR and UV-vis spectroscopy indicate that carbamates can undergo direct reactions with various radical species, oxidizing themselves into radicals in the process. Hence, they are prone to participate in the prolongation step of the radical chain reactions occurring in the soil environment. Theoretical calculations revealed that from the thermodynamic point of view hydrogen atom transfer is the preferred mechanism in the reactions of the two carbamates with the radicals. The activity of carbofuran was determined experimentally (using pseudo-first-order kinetics) and theoretically to be noticeably higher in comparison with carbaryl and comparable with gallic acid. The findings of this study suggest that the radicals present in soil can play an important role in natural remediation mechanisms of carbamates.

Enhancing polymer thermoelectric performance using radical dopants

Abstract Organic thermoelectric materials provide a means to reclaim, in part, potentially lost energy through a solid-state process that converts low-value thermal gradients (in the form of heat) to electricity; however, a new avenue towards improving the performance of these emerging thermoelectric materials must be brought to light before their widespread implementation becomes warranted. Here, we develop a blend of open-shell small molecules and closed-shell, conjugated polymers in order to evaluate how the chemical composition of the distinct open-shell, charge-neutral molecular dopants impacts the thermoelectric performance of a common hole-transporting (p-type) polymer semiconductor, poly(3-hexylthiophene) (P3HT). In doing so, we are able to increase the electrical conductivity of the P3HT composite both with and without affecting the oxidation state of the polymer. Specifically, the electrical conductivity of the conjugated polymer increases without changing the oxidation state of the P3HT when the preferentially-oxidized species 4-hydroxy-2,2,6,6-tetramethylpiperidin-1-oxyl (TEMPO) radical is incorporated into the hole-conducting thin film. Moreover, the inclusion of the preferentially-reduced galvinoxyl (GAV) radical also increases the electrical conductivity of the thin film; however, this small molecule dopant changes the oxidation state of the P3HT moiety. The ability to achieve the gains in the electrical conductivity of P3HT with the TEMPO radical in a manner that is independent of its oxidation state was confirmed using optical spectroscopy, cyclic voltammetry, and x-ray diffraction techniques. Importantly, this ability to enhance the electrical conductivity of P3HT in a manner that is independent of the oxidation state of the polymer provides a means to circumvent the oft-observed inverse relationship between the electrical conductivity and thermopower of the semiconducting polymer, and this combined effect allows for an ∼170-fold increase for the TEMPO-containing composites compared to a ∼70-fold increase for the GAV-containing composites. Thus, the described phenomena for charge-neutral radical dopants provides a set of critical design parameters for future polymer thermoelectric materials and composites, and it opens a new pathway towards high-performance organic thermoelectric devices.

Stepwise sequential analysis of stable multiradicals formation in polyphenolic myricetin active OH groups throughout the antioxidant process to scavenge free radicals

Five galvinoxyl radicals (G) reduction by one polyphenolic myricetin (Myc, 3,3′,4′,5,5′,7-Hexahydroxyflavone) molecule-using EPR method-demonstrated that each Myc should donate at least five H atoms resulted in multiradicals Myc5 (5 G + 1Myc → 5 GH + 1 Myc5). The process that five H atoms donation occurs from different OH sites of Myc lead to appearing of five unpaired valence electrons of Myc5 via two possible different mechanisms. First; concerted five H atoms donation from five different OH groups that directly results in Myc5 radicals (Myc → Myc5). Second; the step-wise radical formation in five different OH groups of Myc (Myc → Myc → Myc2 → Myc3 → Myc4 → Myc5). Computational DFT method was used to analyze all the six different OH groups of Myc which involved in free radical reactions for the purposes of clarification the stable multiradicals Myc5 formation mechanism. The fast semi-empirical combined quantum method, AM1/DFT, as well as full DFT geometry optimization approaches of B3LYP functional DFT/DFT with different basis sets of 6-31G (d), 6-311 + G (d,p) and 6-311 + G (2d,2p) confirmed the stepwise H atom abstraction trend on the main three hydroxyl sites as 4′-O → 4′-O3-O → 4′-O3-O-7O both in the gas and water phase. Spin delocalization over the entire Myc, adding the co-planarity, contributed to the stabilization of respective radical species. The excellent stability of Myc radicals should give an effective chain-breaking antioxidant activity for Myc in biological environment which is expected to have far fewer side effects. These findings may be useful to elucidate the radical scavenging mechanism of other flavonoids regarding to design novel antioxidants.

Synthesis and Free Radical Scavenging Activity of New Hydroxybenzylidene Hydrazines.

Hydroxybenzylidene hydrazines exhibit a wide spectrum of biological activities. Here, we report synthesis and free radical scavenging activity of nine new N-(hydroxybenzylidene)-N′-[2,6-dinitro-4-(trifluoromethyl)]phenylhydrazines. The chemical structures of these compounds were confirmed by 1H-NMR, 13C-NMR, 19F-NMR, IR spectroscopy, LC-MS, and elemental analysis. The prepared compounds were tested for their activity to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH), galvinoxyl radical (GOR), and 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) radicals. The free radical scavenging activity expressed as SC50 values of these compounds varied in a wide range, from a strong to no radical scavenging effect. The most effective radical scavengers were hydroxybenzylidene hydrazines containing three hydroxyl groups in the benzylidene part of their molecules. The prepared compounds were also tested for their activity to inhibit photosynthetic electron transport in spinach chloroplasts. IC50 values of these compounds varied in wide range, from an intermediate to no inhibitory effect.

Synthesis and antioxidant activity of a procyanidin B3 analogue

Proanthocyanidin, an oligomer of catechin, is a natural antioxidant and a potent inhibitor of lectin-like oxidized LDL receptor-1, which is involved in the pathogenesis of arteriosclerosis. We synthesized proanthocyanidin analogue 1, in which the geometry of one catechin molecule in procyanidin B3, a dimer of (+)-catechin, is constrained to be planar. The antioxidant activities of the compounds were evaluated in terms of their capacities to scavenge galvinoxyl radicals, and results demonstrate that while procyanidin was 3.8 times more potent than (+)-catechin, the radical scavenging activity of proanthocyanidin analogue 1 was further increased to 1.9 times that of procyanidin B3. This newly designed proanthocyanidin analogue 1 may be a promising lead compound for the treatment of arteriosclerosis and related cerebrovascular diseases.

Synthesis of imidazo[1,2-a]quinoxalines by double Groebke reactions and inhibitory effects on radicals and DNA oxidation

The o-phenylenediamine, aldehyde, and 2,4,4-trimethylpentan-2-yl isocyanide performed a Groebke 3CR to afford 2-aminoquinoxaline, which can react with an aldehyde and t-butyl isocyanide via another Groebke 3CR to give imidazo[1,2-a]quinoxaline. Exchanging two aldehydes in the sequential Groebke 3CR led to a couple of imidazo[1,2-a]quinoxaline isomer, in which the aldehyde moiety located at 2- or 4-position. The ferrocenyl group at 4-position in imidazo[1,2-a]quinoxaline was found to be active in trapping galvinoxyl radical, while the phenolic hydroxyl group at 2-position played a synergistic role with 4-ferrocenyl or 4-flavonyl group in scavenging 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH). In addition, 4-ferrocenyl with N,N-dimethylaminophenyl group at 2-position was able to quench 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+). Moreover, the combination of 4-ferrocenyl with 2-phenyl group (bearing para-N,N-dimethylamino or hydroxyl group) exhibited high inhibitory effect on DNA oxidation induced by 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH).

The Scavenging of DPPH, Galvinoxyl and ABTS Radicals by Imine Analogs of Resveratrol.

Resveratrol (3,5,4′-trihydroxystilbene) is a phytoalexin produced by plants. Resveratrol is known for its anti-cancer, antiviral and antioxidant properties. We prepared imine analogs of resveratrol ((hydroxyphenyliminomethyl)phenols) and tested their antioxidant activity. All prepared resveratrol analogs were able to scavenge 2,2-diphenyl-1-picrylhydrazyl (DPPH), galvinoxyl radical (GOR) and 2,2′-azino-bis(3-ethylbenzothiazoline)-6-sulphonic acid (ABTS) radicals. The antioxidant activity efficiency correlated with the number and position of hydroxyl groups. The most effective antioxidants were resveratrol analogs containing three hydroxyl groups in the benzylidene part of their molecules. These results provide new insights into the relationship between the chemical structure and biological activity of resveratrol analogs.

Bioactive Compounds of Cold-pressed Thyme (Thymus vulgaris) Oil with Antioxidant and Antimicrobial Properties.

Herbs rich in bioactive phytochemicals were recognized to have biological activities and possess many health-promoting effects. In this work, cold-pressed thyme (Thymus vulgaris L.) oil (TO) was studied for its lipid classes, fatty acid profile, tocols and phenolics contents. Antioxidant activity and radical scavenging potential of TO against free radicals (DPPH(・) and galvinoxyl) was determined. Antimicrobial activity (AA) of TO against food borne bacteria, food spoilage fungi and dermatophyte fungi were also evaluated. Neutral lipids accounted for the main lipid fraction in TO, followed by glycolipids and phospholipids. The major fatty acids in TO were linoleic, oleic, stearic, and palmitic. γ-Tocopherol (60.2% of total tocols) followed by α-tocotrienol (26.9%) and α-tocopherol (9.01% of total tocols) were the main tocols. TO contained high amounts of phenolic compounds (7.3 mg/g as GAE). TO had strong antiradical action wherein 65% of DPPH(・) radicals and 55% of galvinoxyl radical were quenched after 60 min of incubation. Rancimat assay showed that induction time (IT) for TO: sunflower oil blend (1:9, w/w) was 6.5 h, while TO: sunflower oil blend (2:8, w/w) recorded higher IT (9 h). TO inhibited the growth of all tested microorganisms. TO exhibited various degrees of AA against different food borne bacteria, food spoilage fungi and dermatophyte fungi, wherein the highest AA was recorded against dermatophyte fungi and yeasts including T. mentagrophytes (62 mm), T. rubrum (40 mm), and C. albicans (20 mm) followed by food spoilage fungi including A. flavus (32 mm) with minimal lethal concentrations (MLC) ranging between 80 to 320 μg/mL. Furthermore, TO exhibited broad-spectra activity against food borne bacteria including S. aureus (30 mm), E. coli (25 mm) and L. Monocytogenes (20 mm) with MLC ranging between 160 to 320 μg/mL. The results suggest that TO could be used economically as a valuable natural product with novel functional properties in food, cosmetics and pharmaceutical industries.

Cold-pressed oregano (Origanum vulgare) oil: a rich source of bioactive lipids with novel antioxidant and antimicrobial properties

In this investigation, cold-pressed oregano (Origanum vulgare) oil (OO) was studied for its lipid classes, fatty acid profile, tocols and phenolics contents. Radical scavenging potential against DPPH· and galvinoxyl radicals was determined. Antimicrobial properties of OO against foodborne bacteria, food spoilage fungi and dermatophyte fungi were also evaluated. The level of neutral lipids in OO was the highest, followed by glycolipids and phospholipids. The main fatty acids in OO were linoleic, oleic, stearic and palmitic acids. γ-Tocopherol constituted 32.1 % of total measured tocols followed by α-tocotrienol (25.8 %) and γ-tocotrienol (21.3 %). OO contained high amounts of phenolic compounds (5.6 mg/g as GAE). OO had strong antiradical action wherein 72 % of DPPH· radicals and 60 % of galvinoxyl radical were quenched after 60 min of incubation. Rancimat assay showed that induction time (IT) for OO/sunflower oil blend (1:9, v/v) was 6 h, while OO/sunflower oil blend (2:8, v/v) recorded higher IT (8 h). OO inhibited the growth of all tested microorganisms. The highest antimicrobial activity of OO was recorded against the dermatophyte fungi including T. mentagrophytes (42 mm) and T. rubrum (38 mm), followed by food spoilage fungi including A. flavus (36 mm) and C. albi (32 mm) with minimal lethal concentration (MLC) ranging between 40 and 320 μg/mL. OO exhibited also broad-spectra activity against foodborne pathogen bacteria (S. aureus, E. coli, S. enteritidis and L. monocytogenes) with MLC ranging between 160 and 320 μg/mL. The results suggest that OO could be used economically as a valuable natural product with novel functional properties in food, cosmetics and pharmaceutical industries.

Passerini three-component adducts as radical scavengers

Eighteen α-acyloxycarboxamides were produced by Passerini three-component reaction (3CR) in order to reveal sterically synergistic effects among various functional groups on the inhibitory properties of α-acyloxycarboxamides toward DNA oxidation and radicals. In trapping 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+), 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH), and galvinoxyl radical and in inhibiting 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation of DNA, α-acyloxycarboxamides with gallic group exhibited significant activities, which can be further enhanced by incorporation of a ferrocenyl group (derived from ferrocenylmethyl isocyanide) at another tip of the molecule. Therefore, a large volume and electron-abundant isocyanide moiety were able to increase the inhibitory effects of phenolic hydroxyl groups derived from carboxylic acid even in a conjugation-free system.

Introducing ferrocene into imidazo[1,2-a]pyridine by Groebke three-component-reaction for scavenging radicals and inhibiting DNA oxidation

With 2-aminopyridine or quinoline, seven aldehydes, and five isocyanides as reactants, sixteen imidazo[1,2-a]pyridines or quinolines were synthesized by using Groebke three-component-reaction (3CR). The radical-scavenging ability was evaluated by quenching 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS+·), 2,2′-diphenyl-1-picrylhydrazyl radical (DPPH), and galvinoxyl radicals, respectively. Compounds consisting of double ferrocenyl groups coupled with quinoline and ester moieties showed good potencies for scavenging ABTS+· and DPPH, while phenolic hydroxyl groups activated the corresponding imidazo[1,2-a]pyridines to react with galvinoxyl radical. Moreover, the oxidation of DNA was caused by 2,2′-azobis(2-amidinopropane hydrochloride) (AAPH), and all of the synthetic compounds were found to inhibit the DNA oxidation. Especially, the scaffold of imidazo[1,2-a]pyridine exhibited antioxidative effect on the DNA oxidation, while the most active compound was ascribed to double ferrocenyl groups incorporating with imidazo[1,2-a]quinoline. The present results showcased that the ferrocenyl group attaching to the scaffold of imidazo[1,2-a]pyridine or quinoline was beneficial for the antioxidative effect.

Antioxidant Effects of Herbal Tea Leaves from Yacon (Smallanthus sonchifolius) on Multiple Free Radical and Reducing Power Assays, Especially on Different Superoxide Anion Radical Generation Systems.

Yacon (Smallanthus sonchifolius), a native Andean plant, has been cultivated as a crop and locally used as a traditional folk medicine for the people suffering from diabetes and digestive/renal disorders. However, the medicinal properties of this plant and its processed foods have not been completely established. This study investigates the potent antioxidative effects of herbal tea leaves from yacon in different free radical models and a ferric reducing model. A hot-water extract exhibited the highest yield of total polyphenol and scavenging effect on 1,1-diphenyl-2-picryl hydrazyl (DPPH) radical among four extracts prepared with hot water, methanol, ethanol, and ethylacetate. In addition, a higher reducing power of the hot-water extract was similarly demonstrated among these extracts. Varying concentrations of the hot-water extract resulted in different scavenging activities in four synthetic free radical models: DPPH radical (EC50 28.1 μg/mL), 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) cation radical (EC50 23.7 μg/mL), galvinoxyl radical (EC50 3.06 μg/mL), and chlorpromazine cation radical (EC50 475 μg/mL). The yacon tea-leaf extract further demonstrated superoxide anion (O2(-)) radical scavenging effects in the phenazine methosulfate-NADH-nitroblue tetrazolium (EC50 64.5 μg/mL) and xanthine oxidase assay systems (EC50 20.7 μg/mL). Subsequently, incubating human neutrophilic cells in the presence of the tea-leaf extract could suppress the cellular O2(-) radical generation (IC50 65.7 μg/mL) in a phorbol 12-myristate 13-acetate-activated cell model. These results support yacon tea leaves may be a good source of natural antioxidants for preventing O2(-) radical-mediated disorders. Yacon has been considered to be a potent alternative food source for patients who require a dietary cure in regional area, while the leaf part has been provided and consumed as an herbal tea in local markets. We demonstrated here potent antioxidative effects of the tea leaves from yacon in different free radical assays, reducing power assay, and cellular superoxide anion radical generation assay. Results support yacon tea leaves may be a good source of natural antioxidants for preventing O2(-) radical-mediated disorders.

Coumarin-fused coumarin: antioxidant story from N,N-dimethylamino and hydroxyl groups.

Two coumarin skeletons can form chromeno[3,4-c]chromene-6,7-dione by sharing with the C ═ C in lactone. The aim of the present work was to explore the antioxidant effectiveness of the coumarin-fused coumarin via six synthetic compounds containing hydroxyl and N,N-dimethylamino as the functional groups. The abilities to quench 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS(+•)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH), and galvinoxyl radical revealed that the rate constant for scavenging radicals was related to the amount of hydroxyl group in the scaffold of coumarin-fused coumarin. But coumarin-fused coumarin was able to inhibit DNA oxidations caused by (•)OH, Cu(2+)/glutathione (GSH), and 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) even in the absence of hydroxyl group. In particular, a hydroxyl and an N,N-dimethylamino group locating at different benzene rings increased the inhibitory effect of coumarin-fused coumarin on AAPH-induced oxidation of DNA about 3 times higher than a single hydroxyl group, whereas N,N-dimethylamino-substituted coumarin-fused coumarin possessed high activity toward (•)OH-induced oxidation of DNA without the hydroxyl group contained. Therefore, the hydroxyl group together with N,N-dimethylamino group may be a novel combination for the design of coumarin-fused heterocyclic antioxidants.

Optical, Electrical, and Magnetic Studies of Organic Solar Cells Based on Low Bandgap Copolymer with Spin ½ Radical Additives

The charge photogeneration and recombination processes in organic photovoltaic solar cells based on blend of the low bandgap copolymer, PTB7 (fluorinated poly‐thienothiophene‐benzodithiophene) with C60‐PCBM using optical, electrical, and magnetic measurements in thin films and devices is studied. A variety of steady state optical and magneto‐optical techniques were employed, such as photoinduced absorption (PA), magneto‐PA, doping‐induced absorption, and PA‐detected magnetic resonance (PADMR); as well as picosecond time‐resolved PA. The charge polarons and triplet exciton dynamics in films of pristine PTB7, PTB7/fullerene donor–acceptor (D–A) blend is followed. It is found that a major loss mechanism that limits the power conversion efficiency (PCE) of PTB7‐based solar cell devices is the “back reaction” that leads to triplet exciton formation in the polymer donor from the photogenerated charge‐transfer excitons at the D–A interfaces. A method of suppressing this “back reaction” by adding spin½ radicals Galvinoxyl to the D–A blend is presented; this enhances the cell PCE by ≈30%. The same method is not effective for cells based on PTB7/C70‐PCBM blend, where high PCE is reached even without Galvinoxyl radical additives.

Ferrocenyl-appended aurone and flavone: which possesses higher inhibitory effects on DNA oxidation and radicals?

The aim of the present work was to compare the antioxidative effect of the ferrocenyl-appended aurone with that of ferrocenyl-appended flavone; therefore, nine aurones together with the flavone-type analogues were synthesized by using chalcone as the reactant. The radical-scavenging property was evaluated by reacting with the 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonate) cationic radical (ABTS(+·)), 2,2'-diphenyl-1-picrylhydrazyl radical (DPPH), and galvinoxyl radical, respectively. The cytotoxicity was estimated by inhibiting 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH)-induced oxidation of DNA. It was found that the introduction of the ferrocenyl group remarkably increased the radical-scavenging activities of aurone and flavone. Especially, the ferrocenyl group in flavones can quench radicals even in the absence of the phenolic hydroxyl group, while ferrocenyl-appended aurones can efficiently protect DNA against AAPH-induced oxidation. Therefore, the antioxidative effect was generated by the ferrocenyl group and enhanced by the electron-donating group attaching to the para-position of the ferrocenyl group. Introducing the ferrocenyl group into natural compounds may be a useful strategy for increasing the antioxidative effectiveness.

Impact of suppressing the caffeic acid O-methyltransferase (COMT) gene on lignin, fiber, and seed oil composition in Brassica napus transgenic plants

The impact of suppressing the caffeic acid O-methyltransferase (COMT) gene on lignin and fiber content as well as seed oil composition of Brassica napus was studied. Transgenic lines showed significant reduction in COMT enzyme activity ranging between 21 and 31 % residual activity. Lignin in the transgenic Cruciferin:COMT line 34-3 seeds was reduced by 35 % of the wild type, which decreased acid detergent fiber and neutral detergent fiber by 17.92 and 13.04 % of the control, respectively. The main fatty acids were monounsaturated (67.2–69.5 %) followed by polyunsaturated (20.9–23.3 %). The content of tocols ranged between 338 and 440 mg/100 g oil. The highest antiradical action toward 1,1-diphenyl-2-picrylhydrazyl and galvinoxyl radicals was in the oil of the transgenic line 34-3, which contained the highest amount of total phenolic compounds and total tocols. The results show the possibility of reducing lignin in B. napus with no effect on oil content and quality.