Search

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. [ABSTRACT FROM AUTHOR]

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 [ABSTRACT FROM AUTHOR]

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 (H2O2) 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 H2O2: 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. [ABSTRACT FROM AUTHOR]

Pyruvic acid and its derivatives occurring in most biological systems are known to exhibit several pharmacological properties, such as anti-inflammatory, neuroprotective or anticancer, many of which are suggested to originate from their antioxidant and free radical scavenger activity. The therapeutic potential of these compounds is a matter of particular interest, due to their mechanisms of action, particularly their possible antioxidant behaviour. Here, we report the results of a study of the effect of pyruvic acid (PA), ethyl pyruvate (EP) and sodium pyruvate (SP) on reactions generating reactive oxygen species (ROS), such as superoxide anion radicals, hydroxyl radicals and singlet oxygen, and their total antioxidant capacity. Chemiluminescence (CL) and spectrophotometry techniques were employed. The pyruvate analogues studied were found to inhibit the CL signal arising from superoxide anion radicals in a dose-dependent manner with IC50 = 0.0197 ± 0.002 mM for EP and IC50 = 69.2 ± 5.2 mM for PA. These compounds exhibited a dose-dependent decrease in the CL signal of the luminol + H2O2 system over the range 0.5-10 mM with IC50 values of 1.71 ± 0.12 mM for PA, 3.85 ± 0.21 mM for EP and 22.91 ± 1.21 mM for SP. Furthermore, these compounds also inhibited hydroxyl radical-dependent deoxyribose degradation in a dose-dependent manner over the range 0.5-200 mM, with IC50 values of 33.2 ± 0.3 mM for SP, 116.1 ± 6.2 mM for EP and 168.2 ± 6.2 mM for PA. All the examined compounds also showed antioxidant capacity when estimated using the ferric-ferrozine assay. The results suggest that the antioxidant activities of pyruvate derivatives may reflect a direct effect on scavenging ROS and, in part, be responsible for their pharmacological actions. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

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 (O•2), 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 O•2. 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. [ABSTRACT FROM AUTHOR]

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 (O-• 2 ), 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. [ABSTRACT FROM AUTHOR]

ABSTRACT 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 [ABSTRACT FROM AUTHOR]

ABSTRACT Free radical activity towards superoxide anion radical ( [ABSTRACT FROM AUTHOR]

ABSTRACT The direct effect of the four catecholamines (adrenaline, noradrenaline, dopamine and isoproterenol) on superoxide anion radicals ( [ABSTRACT FROM AUTHOR]

ABSTRACT 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 ( kr) of CATs with HO• were found to be in the order of 109 L/mol/s, and the kr value for noradrenaline was the highest ( kr = 8.4 × 109 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. [ABSTRACT FROM AUTHOR]

ABSTRACT 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) × 109 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 [ABSTRACT FROM AUTHOR]

ABSTRACT Carazolol [4-(2-hydroxy-3-isopropyl-amino-propoxy)-carbazole], a β3-adrenoceptor agonist, is clinically used in the treatment of hypertension, cardiac arrhythmias and angina pectoris. Despite the beneficial effect of the drug, its high dose may contribute to cardiotoxicity. This study was conducted to examine whether carazolol can influence hydroxyl radical formation by a Fenton-like reaction [Co(II) + H2O2 + HO-] in the presence of ethylenediaminetetraacetic acid. The oxygen free radicals and singlet oxygen (1O2) formation was traced by three different assay methods: chemiluminescence (CL), an electron spin resonance (ESR) spin trapping with 2,2,6,6-tetramethyl-4-piperidine and 5,5-dimethyl-1-pyrroline-1-oxide, and spectrophotometric determination of 1O2 based on bleaching of p-nitrosodimethylaniline. The effect of hydroxyl radical inhibitors and 1O2 quenchers on peroxidation of carazolol was also examined. The results indicated that carazolol enhanced the HO radical and 1O2 formation in a Fenton-like reaction. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT 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 ( [ABSTRACT FROM AUTHOR]

ABSTRACT A chemiluminescent technique was applied to determine antioxidative activities of adriamycin, farmorubicin, mitomycin C and bleomycin against superoxide anion radical (O2•) in aprotic medium. The antioxidant capacity was expressed as the decrease in light emission from the O2• solution by and antibiotic. A KO2 solution in dimethyl sulphoxide (DMSO) and 18-crown-6 ether were used for the generation of O2•. The results showed that the examined compounds decreased the chemiluminescence (CL) sum from the O2•-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 O2• 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 KO2-DMSO-crown ether system was useful for the evaluation of antioxidant activity in aprotic solvents. Copyright © 2011 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The purpose of this study was to identify the antioxidant activity of 16 compounds isolated from Piper cubeba (CNCs) through the extent of their capacities to scavenge free radicals, hydroxyl radical (HO), superoxide anion radical () and 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), in different systems. Electron paramagnetic resonance (EPR) and 5,5-dimethyl-1-pyrroline- N-oxide, DMPO, as the spin trap, and chemiluminescence techniques were applied. Using the Fenton-like reaction [Fe(II) + HO], CNCs were found to inhibit DMPOOH radical formation ranging from 5 to 57% at 1.25 mmol L concentration. The examined CNCs also showed a high DPPH antiradical activity (ranging from 15 to 99% at 5 mmol L concentration). Furthermore, the results indicated that seven of the 16 tested compounds may catalyse the conversion of superoxide radicals generated in the potassium superoxide/18-crown-6 ether system, thus showing superoxide dismutase-like activity. The data obtained suggest that radical scavenging properties of CNCs might have potential application in many plant medicines. Copyright © 2010 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The scavenging effects of eighteen thiazolyl thiazolidine-2,4-dione compounds (TTCs) on superoxide radical [ABSTRACT FROM AUTHOR]

The antioxidant behavior of a series of new synthesized substituted thiazolyl-thiazolidine-2,4-dione compounds (TZDs) was examined using chemiluminescence and electron paramagnetic resonance spin trapping techniques. 5,5-Dimethyl-1-pyrroline- N-oxide (DMPO) was used as the spin trap. The reactivity of TZDs with superoxide anion radical (O [ABSTRACT FROM AUTHOR]

The hydroxyl radical (HO•)- and superoxide anion radical (O [ABSTRACT FROM AUTHOR]

Bucillamine (BUC) is used clinically for the treatment of rheumatoid arthritis. Some of the pharmacological action of BUC has been reported as being dependent on the production of reactive oxygen species (ROS). In this paper the reactivity of BUC with superoxide anion radical (O2•−) generated from potassium superoxide/18-crown-6 ether dissolved in DMSO, hydroxyl radical (HO•) produced in the Cu2+-H2O2 reaction, peroxyl radical (ROO•) from 2,2′-azobis (2-amidino-propane) dichloride decomposition, and singlet oxygen (1O2) from a mixture of alkaline aqueous H2O2 and acetonitrile, have been investigated. Chemiluminescence, fluorescence, electron paramagnetic resonance (EPR) spin-trapping techniques and the deoxyribose and oxygen radical absorbance capacity towards ROO• (ORACROO) assays were used to elucidate the anti- and pro-oxidative behaviours of BUC towards ROS. The results indicated that BUC efficiently inhibited chemiluminescence from the O2•−-generating system at relatively high concentrations (0.5-2 mmol/L); however, at lower concentrations (<0.5 mmol/L) the drug enhanced light emission. The behaviour of BUC was correlated with a capacity to decrease the chemiluminescence signal from the Cu2+-H2O2 system; scavenging HO• was effective only at high concentrations (1-2 mmol/L) of the drug. Bucillamine also prevented deoxyribose degradation induced by HO• in a dose-dependent manner, reaching maximal inhibition (24.5%) at a relative high concentration (1.54 mmol/L). Moreover, BUC reacts with ROO•; the relative ORACROO was found to be 0.34 µmol/L Trolox equivalents/µmol sample. The drug showed quenching of 1O2-dependent 2,2,6,6-tetramethylpiperidine-N-oxide radical formation from 2,2,6,6-tetramethyl-piperidine (e.g. 90% inhibition was found at 1 mmol/L concentration). The results showed that BUC may directly scavenge ROS or inhibit reactions generating them. However, the drug may have pro-oxidant activity under some reaction conditions. Copyright © 2006 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The plant-derived phenolic compounds genistein and oleuropein are known to exhibit several biological properties, many of which may result from their antioxidant and free radical scavenger activity. In this paper we report the results of a complex study of antioxidant activity of genistein and oleuropein, using electron spin resonance (ESR), chemiluminescence, fluorescence and spectrophotometric techniques. Different reaction systems were applied to study the inhibitory effect of the phenolic compounds studied: (a) the potassium superoxide[sol ]18- crown-6 dissolved in DMSO system, which generates superoxide radical (O2·−) and hydrogen peroxide (H2O2); (b) the Co(II)-EDTA-H2O2 system (the Fenton-like reaction), which generates hydroxyl radical (HO·); (c) 2,2′-azobis(2-amidino-propane)dichloride (AAPH) as the peroxyl radical (ROO·) generator, and the 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical test. Results showed that genistein and oleuropein decreased the chemiluminescence sum from the O2·− generating system, an inhibitory effect that was dependent on their concentration. These compounds also reacted with ROO radicals and they showed activity about two-fold greater than the standard Trolox. The antioxidant effects were studied at different concentrations and reflected in protection against the fluorescence decay of β-phycoerythrin ( β-PE), due to ROO· attack on this protein. Using the Fenton-like reaction and the spin trap agent 5,5-dimethyl-1-pyrroline-N-oxide (DMPO), the phenolic compounds examined were found to inhibit DMPO-·OH radical formation in the range 10-90% at concentrations of 0.1 mmol[sol ]L to 2 mmol[sol ]L. Furthermore, these compounds also inhibited HO·-dependent deoxyribose degradation; about 20% and 60% inhibitions were observed in the presence of 0.5 mmol[sol ]L genistein and oleuropein, respectively. It was also demonstrated that genistein had a weaker DPPH radical scavenging activity than oleuropein. Our results confirm good scavenging activity towards O2·−, HO· and ROO· and the antioxidant effect of genistein and oleuropein. Copyright © 2005 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Indole-2 and 3-carboxamides (IDs) are proposed to be selective cyclooxygenase inhibitors. Since cyclooxygenase-1 may be involved in reactive oxygen species (ROS) production, we hypothesize that these indole derivatives have antioxidative properties. We have employed chemiluminescence (CL) and electron spin resonance (ESR) spin trapping to examine this hypothesis. We report here the results of a study of reactivity of 10 selected indole derivatives towards ROS. The following generators of ROS were applied: potassium superoxide (KO2) as a source of superoxide radicals (O2·−), the Fenton reaction (Co-EDTA/H2O2) for hydroxyl radicals (HO·), and a mixture of alkaline aqueous H2O2 and acetonitrile for singlet oxygen (1O2). Hydroxyl radicals were detected as 5,5-dimethyl-1-pyrroline- N-oxide (DMPO) spin adduct, whereas 2,2,6,6-tetramethyl-piperidine (TEMP) was used as a detector of 1O2. Using the Fenton reaction, 0.5 mmol/L IDs were found to inhibit DMPO-ȮH radical formation in the range 7-37%. Furthermore the tested compounds containing the thiazolyl group also inhibited the 1O2-dependent TEMPO radical, generated in the acetonitrile + H2O2 system. About 20% inhibition was obtained in the presence of 0.5 mmol/L IDs. 1 mmol/L IDs caused an approximately 13-70% decrease in the CL sum from the O2·− generating system (1 mmol/L). The aim of this paper is to evaluate these indole derivatives as antioxidants and their abilities to scavenge ROS. Copyright © 2004 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Background: Stilbene phytalexis (1,2-diphenyloethylen) and benzamide are beneficial for human health. To increase the stilbene ring activity, a new series of its derivatives containing benzamide structure was synthesized and evaluated for their in vitro antioxidant power., Methods: 1H nuclear magnetic resonance, mass spectroscopy, and chromatographic analyses were used to confirm the successful synthesis. The antioxidant properties were determined by the elimination of O 2 ˙-, HO˙ , DPPH˙ , ABTS+˙ radicals, total antioxidant status (TAS) and the ferric reducing antioxidant activities (TAC) measurements., Results: Stilbenebenzamide compounds showed a wide spectrum of antioxidant ability; however, their total antioxidant power was weaker than those of butylated hydroxytoluene (BHT), ascorbic acid, and resveratrol. The highest antiradical activity towards O 2 ˙ and HO˙ was shown by the compounds with structures containing amine group (SBEBA, SBA) (O 2 ˙: 37.7 - 38.0% and 40.8 - 43.5%, HO˙ : 29.8%, 28.7% inhibition, respectively) at1.25 mM concentration. The antiradical power of SBEBA (0.29) in DPPH˙ assay was lower than those of resveratrol (1.83), ascorbic acid (3.63) and BHT (4.09). The TAS values of the synthesized compounds ranged from 152.9±5.3 to 240.2±6.7μM trolox equivalent/gram (TE/g) and were much lower than those of BHT (1304±43.0), reservatrol (1360±29.0) and ascorbic acid (2782±39.7) μM TE/g. Similarly, the TAC values ranging from 29.7±0.9 to 41.5±1.6 μM TE were weaker than that of resveratrol (239.2 ±6.7 μM TE/g)., Conclusion: The results suggest that the presence of the hydroxyl group in the stilbene ring should be considered in the further design of stilbenebenzamide compounds to enhance their antioxidant activity., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.net.)

Background: A new series of 13 piperazinyl flavone derivatives has been synthesized and examined for their in vitro antiradical and antioxidant activities in response to the pharmacy industry's increasing demand for new non-toxic anti-inflammatory and anticancer drugs., Method: Their antioxidant activity was evaluated by the reactive oxygen species (ROS) scavenging assays, 2,2-diphenyl-1-picrylhydrazyl free radical (DPPH•) and 2,2'-azino-bis(3- ethylbenzothiazoline-6-sulphonic acid) radical cation (ABTS+•) scavenging assays, and the ferric reducing antioxidant potency (TAC) method, and was compared to known positive controls, herbal infusions, and penicillins. Chemiluminescence, spectrophotometry, electron spin resonance (ESR) and 5,5-dimethyl-1-pyrroline-1-oxide (DMPO) as the spin trap were the measurement techniques., Result: It was seen that synthesized compounds have a wide spectrum of antioxidant property. Some of the test compounds proved to be extremely efficient scavengers of H2O2 exhibiting, in some cases, EC50 of about 2 µM. The values of antioxidant status (TAS) were in the range of 49 ± 3.9 to 1283 ± 51.3 µM TE/g (TE = Trolox equivalent) and were lower than that of butylated hydroxytoluene (BHT) (1304 ± 43.2 µM TE/g) and green tea (1356 ± 40.0 µM TE/g), but for several synthesized compounds, they were higher than chamomille infusion and penicillins. Ferric reducing antioxidant powers (TAC) for the piperazinyl flavone derivatives were in the range 7 ± 0.5 to 104 ± 0.6 µM TE/g and were weaker than that of BHT (217 ± 5.3 µM TR/g )., Conclusion: Carboxylic or hydroxamic acid substituted piperazinyl flavones are potentially active as antioxidants, thus may be suggested as pharmacologically interesting ones., (Copyright© Bentham Science Publishers; For any queries, please email at epub@benthamscience.org.)

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.)