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• A lightweight vertical lathe with an innovative steel–polymer concrete frame is presented. • A design methodology based on relative tool-workpiece frequency response functions is proposed. • A finite element modeling methodology of a machine tool with a steel–polymer concrete frame is proposed. The paper presents the process of designing a lightweight vertical lathe with a steel–polymer frame. The purpose of using such a frame was to increase the stability of machining. As part of the study presented in this paper, polymer concrete was developed to provide a significant increase in the damping of steel structures (increase in the modal damping ratio for a steel beam by 239% and 81% reduction in the amplitude of the receptance function for the dominant resonance). Finite element models of lathes with steel–polymer concrete frame were built in three variants differing in polymer concrete filling distribution. Vulnerability of the machine tool variants to regenerative chatter instability was evaluated using frequency response functions calculated at tool-workpiece contact point. On the basis of the solution guaranteeing the highest stability of machining, a prototype lathe was built, subjecting model to experimental verification. The prototype lathe was characterized by up to 83% (on average 55%) reduction of relative tool-workpiece frequency response functions amplitudes, compared to steel variant. [ABSTRACT FROM AUTHOR]

In the framework of the performed studies, the antibacterial activity of the following fungicides was evaluated: Miedzian 50 WG (active substance -- a.s. 50% copper oxychloride), Ridomil MZ Gold 68 WG (a.s. 3.8% metalaxyl-M and 64%, mancozeb), Euparen Multi 50 WG (a.s. 50% tolylfluanid), Captan 80 WG [a.s. 80% N-(captan)], Dithane Neotec 75 WG (a.s. 75% mancozeb). The evaluation also concerned the essential oils: lavender, sage, lemon balm, clove, and a preparation based on thyme oil (BioZell). Each preparation and compound was tested against the following bacterial pathogens: Erwinia amylovora, Xanthomonas arboricola pv. corylina, X. arboricola pv. juglandis, Pseudomonas syringae pv. syringae, Agrobacterium tumefaciens (presently Rhizobium radiobacter). Each preparation and compound was tested at a concentration of 1,000 ppm of active substance. Copper oxychloride was also tested at a concentration of 1,500 ppm. Among the tested fungicides, metalaxyl-M with mancozeb, mancozeb alone, and copper oxychloride inhibited all of the tested strains of pathogenic bacteria. Tolylfluanid did not inhibit any of the bacteria used. Out of the investigated essential oils, the strongest inhibitors of bacteria were: sage, cloves, and BioZell. The protective activity of the above mentioned fungicides was also evaluated in vivo. They were assessed against fire blight on apple blossoms and pear fruitlets, against bacterial canker on sweet cherry fruitlets, and against crown gall on sunflower seedlings (the test plant). All fungicides were applied at the same concentrations as those in the in vitro tests. Only copper oxychloride was found to show protective activity against the studied diseases. This result indicates that the antibacterial properties of the other fungicides did not correspond with their activity on the plant organs used in the in vivo experiment. [ABSTRACT FROM AUTHOR]

Three nCo,N-TiO2 nanocomposites (where cobalt concentration index n = 1, 5 and 10 wt %) were prepared and investigated by magnetic resonance spectroscopy at room temperature. Ferromagnetic resonance (FMR) lines of magnetic cobalt agglomerated nanoparticle were dominant in all registered spectra. The relaxation processes and magnetic anisotropy of the investigated spin system essentially depended on the concentration of cobalt ions. It is suggested that the samples contained two magnetic types of sublattices forming a strongly correlated spin system. It is suggested that the existence of strongly correlated magnetic system has an essential influence of the photocatalytic properties of the studied nanocomposites.

Iron and nitrogen co-modified titanium dioxide nanocomposites, nFe,N-TiO2 (where n = 1, 5 and 10 wt% of Fe), were investigated by detailed dc susceptibility and magnetization measurements. Different kinds of magnetic interactions were evidenced depending essentially on iron loading of TiO2. The coexistence of superparamagnetic, paramagnetic and ferromagnetic phases was identified at high temperatures. Strong antiferromagnetic interactions were observed below 50 K, where some part of the nanocomposite entered into a long range antiferromagnetic ordering. Antiferromagnetic interactions were attributed to the magnetic agglomerates of iron-based and trivalent iron ions in FeTiO3 phase,whereas ferromagnetic interactions stemmed from the F-center mediated bound magnetic polarons.

Background: A series of eight new flavone derivatives containing a piperazine chain with different substitution were synthesized and their structures were determined., Methods: Their antiradical and antioxidant activities were evaluated using superoxide anion radical, hydroxyl radical, 2,2-diphenyl-1-picrylhydrazyl radical, 2,2'-azino-di(3-ethylbenzthiazoline sulphonate) radical cation (ABTS + ) scavenging (as measure total antioxidant status TAS), ferric reducing antioxidant power (TAC), and hydrogen peroxide decomposition. The antioxidant activities of the synthesized compounds were compared with standard antioxidants trolox, ascorbic acid, butylated hydroxytoluene (BHT) as positive controls, reference antibiotics (doxycycline, dicloxacillin), and medicinal plants (Menthae piperita, Cistus incanus). Chemiluminescence, spectrophotometry, electron spin resonance (ESR) spectroscopy in conjunction with 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as the spin trap were the measurement techniques., Results: The results show that the synthesized compounds exhibit weak, albeit a wide spectrum of antiradical and antioxidant activities. The TAS values were measured as trolox equivalents, ranging from 209.6 ± 6.1 to 391.1 ± 8.2 µM TE/g; the TAC values were in ranges from 10.8 ± 0.5 to 49.5 ± 0.5 µM TE/g being higher than that of dicloxacillin (241.0 ± 16.5 and 9.73 ± 0.8 µM TE/g, respectively), but lower than ascorbic acid, BHT, doxycycline, and medicinal plants. Best antioxidant activities were found for the piperazinyl analogues with methoxy group on phenyl piperazine ring., Conclusion: We suggest that the synthesized compounds may be used as lead molecules for optimization of molecular structure to maximize the antioxidant potency., Competing Interests: Declaration of Competing Interest The authors declare no conflict of interest., (Copyright © 2019 Elsevier Inc. All rights reserved.)

Aim: Synthesis of novel 2(2-hydroxyphenyl) pyrimidine/benzothiazole piperazinyl-substituted flavones end evaluate their antioxidant activity., Results: Six novel 2-(2-hydroxyphenyl) pyrimidine/benzothiazole-substituted flavones were synthesized, their structures were confirmed by elementary and spectral analyses. The compounds were evaluated for their in vitro antioxidant potency by employing various antioxidant assays., Conclusion: All tested compounds acted as scavengers of free radicals like hydroxyl (15-45%), 2,2-diphenyl-1-picrylhydrazyl • (17-48%) at 1.25 and 0.5 mM concentrations respectively. The total antioxidant status activity values of the compounds ranged from 234.1 to 464.1 μm trolox equivalent/g, the total antioxidant capacity - from 24.9 to 52.7 μm trolox equivalent per gram. Compounds incorporating the benzothiazole group on the piperazine ring were more effective antioxidants than those with the 2-(2-hydroxyphenyl) pyrimidine group.

Flavones exhibit a variety of beneficial effects and are well known for their medicinal importance in several diseases, including cardiovascular, neurodegenerative and cancer. The inclusion of the piperazine ring to the flavone backbone is an important strategy in drug discovery but only a few studies have synthesized piperazinyl flavone compounds to test their biological activity. While there is a major focus on the antioxidant properties of drugs in therapy of several diseases of inflammatory origin, we synthesized a series of the novel piperazinyl flavone analogues bearing the phenyl ring with different substituents. The analogues were evaluated for in vitro antioxidant activity against superoxide anion radical, hydroxyl radical, 2,2-diphenyl-1-picrylhydrazyl radical, and hydrogen peroxide scavenging properties. The total antioxidant status based on the absorbance of the 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS +• ) and total antioxidant capacity using the Fe(III)-ferrozine complex were also monitored. The results of the above studies showed that the compounds synthesized were found possessed moderate radical scavenging potential, and that their interaction with reactive oxygen species is complex and depends on their structural conformation and the type of substituent R in the piperazine ring being attached. Best antiradical activity were found for the compounds with methoxy groups on the phenyl ring of substituent R, whereas the presence of methoxy or trifluoromethyl groups in substituent R resulted in higher ABTS +• and ion Fe(III) reduction. These compounds are promising molecules to be used for their antioxidant properties and may be regarded, after improvement of the antioxidant potential, to control diseases of free radical etiology., (Copyright © 2017 John Wiley & Sons, Ltd.)

The aim of this study was to characterize the antioxidant activity of penicillin G (PG), ampicillin (AMP), oxacillin (OX) and dicloxacillin (DOX) through their reactivity towards reactive oxygen species (superoxide anion radical, O2•̅; hydroxyl radical, HO • ; peroxyl radical, ROO • ; hydrogen peroxide, H 2 O 2 ; DPPH • ) using various in vitro antioxidant assays with chemiluminescence (CL) and spectrophotometry as measurement techniques. In hydroxyl radical assays , PG, OX and AMP were found to inhibit the CL signal arising from the Fenton-like reaction in a dose-dependent manner with IC 50  = 0.480 ± 0.020 mM, IC 50  = 0.569 ± 0.021 mM, and IC 50  = 0.630 ± 0.019 mM, respectively. The highest reactivity of PG among the tested penicillins towards the HO radical was confirmed in the deoxyribose degradation assay. In the ABAP-derived ROO radical assay, the radical-scavenging ability of the test penicillins was in the following order: AMP > PG > DOX > OX. The number of reduced DPPH radicals by the drugs tested was <1 being the biggest for PG. The weak antioxidant capacity of the test penicillins was confirmed in the trolox antioxidant capacity assay (0.075 ± 0.004; 0.093 ± 0.006; 0.123 ± 0.005; 0.126 ± 0.004) for OX, AMP, DOX, PG, respectively. Use of luminol as a CL probe for estimation of penicillin reactivity towards H 2 O 2 showed that only AMP was able to quench light emission; the remaining antibiotics demonstrated a strong enhancing effect. All the examined compounds showed a weak antioxidant potential when estimated using the ferric-ferrozine assay. This study is the first to report the evaluation of test penicillins as antioxidants under the same reaction conditions., (Copyright © 2016 John Wiley & Sons, Ltd.)

Isoflavones genistein and daidzein are nonsteroidal phytoestrogens occurring mainly in soybean foods. These phytoestrogens possess estrogenic properties and show a variety of health benefits as anti-inflammatory agents. However, the mechanism of their action has not been identified in detail. The aim of this study is to characterize the antioxidant powers of genistein, daidzein and daidzein metabolite-equol through their activities to scavenge superoxide anion radical (O(•) 2 (-) ), hydroxyl radical (HO(•) ), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH(•) ) and hydrogen peroxide (H2 O2 ) using chemiluminescence and spectrophotometry techniques. Potassium superoxide in dimethyl sulphoxide (DMSO) and 18-crown-6 ether were used as a source of O(•) 2 (-) . Hydroxyl radicals were produced using the Fenton reaction. In free radical assays, genistein had the IC50 values (an amount of antioxidant concentration required to decrease the initial radical concentration by 50%) 0.391 ± 0.012 mM for O(•) 2 (-) , 0.621 ± 0.028 mM for HO(•) and 1.89 ± 0.16 mM for DPPH(•) . The IC50 values for daidzein for these free radicals were 1.924 ± 0.011 mM, 0.702 ± 0.012 mM and 2.81 ± 0.03 mM, respectively. Equol was the most active the free radical scavenger with IC50  = 0.451 ± 0.018 mM for HO(•) and IC50  = 1.36 ± 0.11 mM for DPPH(•) . All tested compounds exerted a significant effect on the H2 O2 : IC50  = 18.1 ± 1.1 μM for genistein, IC50  = 2.1 ± 0.5 μM for daidzein, and IC50  = 1.06 ± 0.2 μM for equol. These findings show that genistein, daidzein and equol are effective free radical scavengers and possess high antioxidant power in vitro. Copyright © 2016 John Wiley & Sons, Ltd., (Copyright © 2016 John Wiley & Sons, Ltd.)

Fifteen chromonylrhodamine derivatives (CRs) were synthesized and the antioxidant activity levels were evaluated for the first time. The antioxidant activity potencies of these chromone derivatives were evaluated towards superoxide anion radicals, hydroxyl radicals and 2,2-diphenyl-1-picrylhydrazyl radicals. Also, the total antioxidant capacity of the tested compounds was measured using the ferric-ferrozine assay. The antioxidant activities were investigated using a chemiluminescence (CL) assay, spectrophotometry measurements, direct electron paramagnetic resonance (EPR) and the EPR spin-trapping technique. The 5,5-dimethyl- 1-pyrroline-1-oxide (DMPO) was applied as spin trap. Eleven of the 15 chromone compounds exhibited a decrease in the CL accompanying the superoxide anion radical produced in anhydrous dimethylsulfoxide (DMSO), ranging from 71-94% at concentration of 1 mmol /L; four of these compounds enhanced light emission in the range 231-672%. Similarly, these compounds caused 28-58% inhibition in the intensity of the DMPO-OOH radical EPR signal and the DMPO-OH radical (from 12-48%). Furthermore, three of these compounds showed very good antioxidant response towards the DPPH radical (EC50 : 0.51-0.56 µmol/L) and the high reduction potentials. These findings demonstrate that the chromone compounds tested may be considered as effective free radicals scavengers, a finding that is of great pharmacological importance., (Copyright © 2014 John Wiley & Sons, Ltd.)

Early diagnosis and treatment of early caries lesions are the basic tenets of minimally invasive dentistry. One of the key elements of a biological approach is the usage of remineralizing agents, which are great alternative to surgical intervention. This article shows a review of the literature concering materials used for the treatment of early caries lesions.

The most important issue in modern cariology is the early diagnostics of carious lesions, because only early detected lesions can be treated with as little intervention as possible. This is extremely difficult on approximal surfaces because of their anatomy, late onset of pain, and very few clinical symptoms. Modern diagnostic methods make dentists' everyday work easier, often detecting lesions unseen during visual examination. This work presents a review of the literature on the subject of modern diagnostic methods that can be used to detect approximal caries.

A series of flavonyl-2,4-thiazolidinedione, imidazolidinedione and rhodanine derivatives were tested for their antioxidant activity as scavengers of oxygen free radicals. Free radical scavenging activities, including superoxide anion radical O2•, hydroxyl radical (HO(•)) and 2,2'-diphenyl-1-picrylhydrazyl free radical have been evaluated using chemiluminescence, electron paramagnetic resonance and spin trapping with 5,5-dimethyl-1-pyrroline-1-oxide as a spin trap. Potassium superoxide in dimethylsulfoxide and 18-crown-6 ether were used for the production of O2•. Hydroxyl radical was generated using the Fenton reaction. Ten of the eleven examined compounds exhibited decrease in chemiluminescence, but there were large differences in the decrease, ranging from 16% to 89%; also, two of these compounds increased light emission by about 200%. On the contrary, all compounds tested exhibited 30-68% scavenging HO(•) and 25-96% scavenging the DPPH(•) radical respectively. Possible mechanisms are proposed to explain the results., (Copyright © 2014 John Wiley & Sons, Ltd.)

Recent reviews evidence that the naturally occurring compounds containing the chromone skeleton exhibit antiradical activities, providing protection against oxidative stress. The antioxidant activities of 13 new synthesized chromonyl-2,4-thiazolidinediones, chromonyl-2,4-imidazolidinediones and chromonyl-2-thioxoimidzolidine-4-ones were evaluated using in vitro antioxidant assays, including superoxide anion radical (O2(-•)), hydroxyl radical (HO(•)), 2,2-diphenyl-1-picryl-hydrazyl free radical (DPPH(•)) scavenging capacity and total antioxidant capacity ferric ion reducing activity. Superoxide anion radical was produced using potassium superoxide/18-crown-6-ether dissolved in dimethylsulfoxide, and the Fenton-like reaction (Fe(II) + H2O2) was a generator of hydroxyl radicals. Chemiluminescence, spectrophotometry, electron paramagnetic resonance (EPR) and 5,5-dimethyl-1-pyrroline-N-oxide (DMPO) as the spin trap were the measurement techniques. The results showed that the majority of the chromone derivatives tested showed a strong scavenging effect towards free radicals, similar to the chemiluminescence reaction with superoxide anion radical with a high activity, inhibition of the DMPO-OOH radical EPR signal (24-58%), the DMPO-OH radical EPR signal (4-75%) and DPPH radical EPR signal (6-100%) at 1 mmol/L. Several of the examined compounds exhibited the high reduction potentials. The results obtained show that the new synthesized chromone derivatives may directly scavenger reactive oxygen species and thus may play a protective role against oxidative damage., (Copyright © 2014 John Wiley & Sons, Ltd.)

The benefits of antioxidants on human health are usually ascribed to their potential ability to remove reactive oxygen species providing protection against oxidative stress. In this paper the free radicals scavenging activities of nine 6-methyl 3-chromonyl derivatives (CMs) were evaluated for the first time by the chemiluminescence, electron paramagnetic resonance, spin trapping and 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) methods. The total antioxidant capacity was also measured using a ferric-ferrozine reagent. Compounds having a hydrogen atom at the N3-position of the β-ring were effective in quenching CL resulted from the KO2 /18-crown-6-ether system (a source of superoxide anion radical, O2•¯) in a dose-dependent manner over the range of 0.05-1 mmol/L [IC50 ranged from 0.353 (0.04) to 0.668 (0.05) mmol/L]. The examined compounds exhibited a significant scavenging effect towards hydroxyl radicals (HO(•) HO(•)), produced by the Fenton reaction, and this ranged from 24.0% to 61.0%, at the concentration of 2.5 mmol/L. Furthermore, the compounds examined were also found to inhibit DPPH(•) and this ranged from 51.9% to 97.4% at the same concentration. In addition, the use of the total antioxidant capacity assay confirmed that CM compounds are able to act as reductants. According to the present study, CM compounds showed effective in vitro free radical scavenging activity and may be considered as potential therapeutics to control diseases of oxidative stress-related etiology., (Copyright © 2013 John Wiley & Sons, Ltd.)

Free radical activity towards superoxide anion radical (O2•¯), hydroxyl radical (HO(•)) and 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) of a series of novel thiazolidine-2,4-dione derivatives (TSs) was examined using chemiluminescence, electron paramagnetic resonance (EPR) and EPR spin trapping techniques. 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) was applied as the spin trap. Superoxide radical was produced in the potassium superoxide/18-crown-6 ether dissolved in dimethyl sulfoxide. Hydroxyl radical was generated in the Fenton reaction (Fe(II) + H2O2. It was found that TSs showed a slight scavenging effect (15-38% reduction at 2.5 mmol/L concentration) of the DPPH radical and a high scavenging effect of O2•¯ (41-88%). The tested compounds showed inhibition of HO(•)-dependent DMPO-OH spin adduct formation (the amplitude of EPR signal decrease ranged from 20 to 76% at 2.5 mmol/L concentration. Our findings present new group compounds of relatively high reactivity towards free radicals., (Copyright © 2012 John Wiley & Sons, Ltd.)

The direct effect of the four catecholamines (adrenaline, noradrenaline, dopamine and isoproterenol) on superoxide anion radicals (O2•) was investigated. The reaction between 18-crown-6-ether and potassium superoxide in dimethylsulfoxide was used as a source of O2•. The reactivity of catecholamines with O2• was examined using chemiluminescence, reduction of nitroblue tetrazolium and electron paramagnetic resonance spin-trapping techniques. 5,5-Dimethyl-1-pyrroline-N-oxide was included as the spin trap. The results showed that the four catecholamines were effective and efficient in inhibiting chemiluminescence accompanying the potassium superoxide/18-crown-6-ether system in a dose-dependent manner over the range 0.05-2 mM in the following order: adrenaline > noradrenaline > dopamine > isoproterenol, with, IC50 = 0.15 ± 0.02 mM 0.21 ± 0.03 mM, 0.27 ± 0.03 mM and 0.50 ± 0.04 mM, respectively. The catecholamines examined also exhibited a strong scavenging effect towards O2• when evaluated this property by the inhibition of nitroblue tetrazolium reduction (56-73% at 1 M concentration). A very similar capacity of O2• scavenging was monitored in the 5,5-dimethyl-1-pyrroline-N-oxide spin-trapping assay. The results suggest that catecholamines tested may involve a direct effect on scavenging O2- radicals., (Copyright © 2013 John Wiley & Sons, Ltd.)

The direct effects of the four catecholamines (CATs), adrenaline (A), noradrenaline (NA), dopamine (D) and isoproterenol (I), on free radicals were investigated using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) and hydroxyl radial (HO(•)). The CATs examined were found to inhibit the ESR signal intensity of DPPH(•) in a dose-dependent manner over the range 0.1-2.5 mmol/L in the following order: NA > A > I > D, with IC50= 0.30 ± 0.03 for noradrenaline and IC50= 0.86 ± 0.02 for dopamine. Hydroxyl radicals were produced using a Fenton reaction in the presence of the spin trap 5,5-dimethyl-1-pyrroline N-oxide (DMPO), and ESR technique was applied to detect the CATs reactivity toward the radicals. The reaction rates constant (k(r)) of CATs with HO(•) were found to be in the order of 10(9)  L/mol/s, and the k(r) value for noradrenaline was the highest (k(r)= 8.4 × 10(9)  L/mol/s). The CATs examined exhibited also a strong decrease in the light emission (62-73% at 1 mmol/L concentration and 79-89% at 2 mmol/L concentration) from a Fenton-like reaction. These reactions may be relevant to the biological action of these important polyphenolic compounds., (Copyright © 2012 John Wiley & Sons, Ltd.)

Tetracyclines are the second most common antibiotic family in medicine usage. These antibiotics exhibit antioxidant potential; however, the exact mechanism remains unclear. The antiradical activity of the seven tetracyclines (TCs; tetracycline, chlortetracycline, oxytetracycline, doxocycline, methacycline, demeclocycline, minocycline) was determined using the free radical 2,2-diphenyl-1-picrylhydrazyl (DPPH(•)) and hydroxyl radicals (HO(•)) generated in a Fenton reaction. Electron spin resonance (ESR), ESR spin-trapping, chemiluminescence and spectrophotometry techniques were applied. It was found that the TCs showed high DPPH antiradical activity in the range 26-96% at 2.5 mmol/L concentration. The second-order rate constants for the reaction between HO(•) and TCs were calculated, in the range (3.6-9.6) × 10(9)  L/mol/s. The tetracycline compounds also exhibited a strong decrease in light emission (range 61-85% at concentration of 1 mmol/L). This study also showed that TCs promote the generation of singlet oxygen in the presence of H(2)O(2) and Fe(II)/Fe(III) ions. Our findings suggest direct scavenging activity of the examined tetracyclines towards free radicals, and may be relevant to therapeutic strategy., (Copyright © 2011 John Wiley & Sons, Ltd.)

A chemiluminescent technique was applied to determine antioxidative activities of adriamycin, farmorubicin, mitomycin C and bleomycin against superoxide anion radical (O(2)(•)) in aprotic medium. The antioxidant capacity was expressed as the decrease in light emission from the O(2)(•) solution by and antibiotic. A KO(2) solution in dimethyl sulphoxide (DMSO) and 18-crown-6 ether were used for the generation of O(2)(•). The results showed that the examined compounds decreased the chemiluminescence (CL) sum from the O(2)(•)-generating system in a dose-dependent manner. Among the antibiotics examined, adriamycin, farmorubicin and bleomycin exhibited antioxidant activity almost comparable to that of 1,2-dihydroxy benzene-3,5-disulphonic acid (tiron), an efficient of the O(2)(•) inhibitor. Mitomycin C was two-times less effective as tiron in decreasing the initial CL intensity. The proposed assay with usage of ultraweak CL technique and the KO(2)-DMSO-crown ether system was useful for the evaluation of antioxidant activity in aprotic solvents., (Copyright © 2011 John Wiley & Sons, Ltd.)

The tetracycline family antibiotics are widely used as human and veterinary treatments. The drugs are effective as antibiotics and also show antimicrobial and non-microbial action. However, the antioxidant properties of tetracyclines have not been characterized in aprotic media. To better understand their biological functions, the in vitro superoxide anion radical (O2•¯) scavenging activities of tetracycline, chlortetracycline, oxytetracycline, doxycycline and methacycline were characterized, along with a very efficient O2•¯ scavenger, tiron, in dimethyl sulphoxide (DMSO), using ultra-weak chemiluminescence (CL). We found that tetracycline, chlortetracycline and doxycycline efficiently inhibited CL from the O2•¯-generating system at concentration levels of 0.02-1.0 mmol/L. Methacycline and oxytetracycline were the O2•¯ scavengers at concentration levels of 0.01-0.1 mmol/L, whereas when their concentration was lowered the drugs were capable of generating O2•¯, leading to CL enhancement. For all the data obtained in this study, the scavenging activity for the compounds tested decreased in the following order: tetracycline > doxycycline > chlortetracycline > tiron methacycline > oxytetracycline. These results indicate that the tetracycline drugs directly alter O2•¯ redox chemistry in aprotic media., (Copyright © 2011 John Wiley & Sons, Ltd.)