Galvinoxyl method for standardizing electron and proton donation activity

Evaluation of Decay Kinetics of Black Elderberry Antioxidants from Fruits and Flowers

The health-promoting properties of black elderberry are related to its high content of polyphenols (natural antioxidants), which eliminate free radicals and prevent the formation of oxidative stress responsible for many diseases. The aim of this work was to determine, the anti-radical effect of Sambucus nigra infusions based on the reaction with 2,2-diphenyl-1-picrylhydrazyl (DPPH) and galvinoxyl (Glv) radicals and to determine the function describing the disappearance curves of these radicals. The antioxidant properties of infusions obtained from the flowers and fruits of this plant were tested using the modified Brand-Williams method using DPPH and Glv radicals. Higher antioxidant activity towards both the DPPH and Glv radicals was found in flowers compared to fruits. In addition, it was found that the process of quenching radicals in the reaction with Sambucus nigra infusions proceeds in accordance with the assumptions of second-order reaction kinetics. The infusion obtained from flowers quenched radicals faster than fruit infusions. The applied second-order kinetics equation may enable estimation of antioxidants levels in natural sources of radicals.

A Multi-Approach Study of Phytochemicals and Their Effects on Oxidative Stress and Enzymatic Activity of Essential Oil and Crude Extracts of Rosmarinus officinalis

Rosmarinus officinalis or Rosemary is a highly valued medicinal vegetal, owing to its notable antispasmodic, anti-inflammatory, and antibacterial properties. In the current work, we aimed to identify the chemical components of the essential oil (EO) of R. officinalis and evaluate its biological properties using an in vitro approach. High performance liquid chromatography time-of-flight mass spectrometry (HPLC-TOF-MS) was utilized to analyze of the hydro-methanolic extract (HME), while gas chromatography–mass spectrometry (GC/MS) was considered during the analysis of the EO’s chemical composition. The antioxidant abilities of HME and the EO were assessed using diverse tests (DPPH, ABTS, GOR, CUPRAC, and FRAP). The anti-enzymatic properties were tested by the inhibition of cholinesterases, α-glucosidase, and tyrosinase enzyme. The HPLC-TOF-MS displayed the existence of flavonoids like luteolin glucuronide I and II, and a few known hydroxycinnamic acids. The EO contained three major components, namely, eucalyptol (28.7%), camphor (16.7%), and borneol (13.5%). The HME had a high total polyphenol content, as determined by the Folin–Ciocalteau method (335.37 ± 9.33 µg of gallic acid eq·mg−1). Notably, the analysis of the bioactivities of the HME and EO revealed comparatively that they possessed higher radical scavenging capacity in the DPPH, ABTS, and galvinoxyl assays, while EO exhibited a higher capacity for enzyme inhibition. Overall, our findings suggest that both the EO and HME extract of Algerian’s R. officinalis holds great usefulness in the pharmaceutical and nutraceutical fields due to its elevated polyphenol content and potent bioactivities.

Phytochemicals, Antioxidant and Antimicrobial Potentials and LC-MS Analysis of Centaurea parviflora Desf. Extracts

Centaurea parviflora (C. parviflora), belonging to the family Asteraceae, is an Algerian medicinal plant used in folk medicine to treat different diseases related to hyperglycemic and inflammatory disorders, as well as in food. The present study aimed to assess the total phenolic content, in vitro antioxidant and antimicrobial activity and phytochemical profile of the extracts of C. parviflora. The extraction of phenolic compounds from aerial parts was conducted using solvents of increasing polarity starting from methanol, resulting in crude extract (CE), to chloroform extract (CHE), ethyl acetate extract (EAE) and butanol extract (BUE). The total phenolic, flavonoid and flavonol contents of the extracts were determined using the Folin-Ciocalteu and AlCl₃ methods, respectively. The antioxidant activity was measured with seven methods: 2,2-diphenyl-1-picrylhydrazyl (DPPH) assay, galvinoxyl free-radical-scavenging test, 2,2'-Azino-Bis(3-Ethylbenzothiazoline-6-Sulfonic Acid) (ABTS) assay, cupric reducing antioxidant capacity (CUPRAC), reducing power, Fe⁺²-phenanthroline reduction assay and superoxide-scavenging test. The disc-diffusion method aimed at testing the sensitivity of bacterial strains toward our extracts. A qualitative analysis with thin-layer chromatography of the methanolic extract was performed. Moreover, HPLC-DAD-MS was used to establish the phytochemical profile of the BUE. The BUE was found to contain high amounts of total phenolics (175.27 ± 2.79 µg GAE/mg E), flavonoids (59.89 ± 0.91 µg QE/mg E) and flavonols (47.30 ± 0.51 µg RE/mg E). Using TLC, different components such as flavonoids and polyphenols were noted. The highest radical-scavenging ability was recorded for the BUE against DPPH (IC₅₀ = 59.38 ± 0.72 µg/mL), galvinoxyl (IC₅₀ = 36.25 ± 0.42 µg/mL), ABTS (IC₅₀ = 49.52 ± 1.54 µg/mL) and superoxide (IC₅₀ = 13.61 ± 0.38 µg/mL). The BUE had the best reducing power according to the CUPRAC (A_0.5 = 71.80 ± 1.22 μg/mL), phenanthroline test (A_0.5 = 20.29 ± 1.16 μg/mL) and FRAP (A_0.5 = 119.17 ± 0.29 μg/mL). The LC-MS analysis of BUE allowed us to identify eight compounds including six phenolic acids and two flavonoids: quinic acid, five chlorogenic acid derivatives, rutin and quercetin 3-o-glucoside. This preliminary investigation revealed that the extracts of C. parviflora have a good biopharmaceutical activity. The BUE possesses an interesting potential for pharmaceutical/nutraceutical applications.

Evaluation of Possible Antioxidant, Anti-Hyperglycaemic, Anti-Alzheimer and Anti-Inflammatory Effects of Teucrium polium Aerial Parts (Lamiaceae)

Teucrium polium L. is commonly used in folk medicine to treat hypertension and diabetes and to heal wounds. The present work aimed to evaluate the different biological activities of T. polium hydroalcoholic extract, its total phenol and flavonoid content, and its mineral elements. Results showed that T. polium extract showed significant antioxidant potential in 2-diphenyl-1-picrylhydrazyl (DPPH) assay with IC₅₀ equal to 8.68 μg/mL but with moderate activity in galvinoxyl assay with IC₅₀ of 21.82 μg/mL and mild activity in the β-carotene assay. It also showed a pronounced anti-hyperglycemic activity using α-amylase inhibitory assay (IC₅₀ = 111.68 µg/mL) and exceeds that of acarbose. T. polium showed excellent activity against acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) with IC₅₀ values of 28.69 and 4.93 μg/mL, respectively, postulating its promising anti-Alzheimer potential. The plant extract exhibited a strong anti-inflammatory effect with Bovine Serum Albumin (BSA) denaturation inhibitory potential estimated by 97.53% at 2 mg/mL, which was further confirmed by the in vivo carrageen-induced edema model. The extract revealed its richness in flavonoids and phenols, evidenced by its polyphenols content (36.35 ± 0.294 μg GAE/mg) and flavonoids (24.30 ± 0.44 μg QE/mg). It is rich in minerals necessary for human health, such as calcium, potassium, iron, sodium, magnesium, manganese and zinc. Molecular docking performed for previously identified compounds on human α-amylase, 5-lipoxygenase (5-LOX) and acetylcholine esterase confirmed the results. Thus, it can be concluded that T. polium can be a good candidate for alleviating many health-debilitating problems and can be highly beneficial in the pharmaceutical industry and medical research.

Antioxidant action of persulfides and polysulfides against free radical-mediated lipid peroxidation

Hydrogen sulfide, hydropersulfides, and hydropolysulfides have been revealed to play important physiological roles such as cell signaling and protection against oxidative stress, but the underlying mechanisms and dynamics of action remain elusive. It is generally accepted that these species act by two-electron redox mechanisms, while the involvement of one-electron redox chemistry has received less attention. In this study, the radical-scavenging activity of hydrogen persulfide, hydrogen polysulfides (HS_nH n = 2-4), and diallyl- or dialkyl-sulfides (RS_nR, n = 1-4) was measured. Furthermore, their antioxidant effects against free radical-mediated human plasma lipid peroxidation were assessed by measuring lipid hydroperoxides. It was found that disodium disulfide, trisulfide, and tetrasulfide acted as potent peroxyl radical scavengers, the rate constant for scavenging peroxyl radical being 3.5 × 10⁵, 4.0 × 10⁵, and 6.0 × 10⁵ M^-1 s^-1 in PBS pH 7.4 at 37 °C respectively and that they inhibited plasma lipid peroxidation efficiently, the efficacy is increased with the catenation number. Disodium tetrasulfide was 1.5 times as reactive as Trolox toward peroxyl radical and inhibited plasma lipid peroxidation more efficiently than ascorbate and Trolox. On the other hand, diallyl- and dialkyl-sulfides did not exert significant radical-scavenging activity, nor did they inhibit lipid peroxidation efficiently, except for diallyl tetrasulfide, which suppressed plasma lipid peroxidation, despite less significantly than disodium tetrasulfide. Collectively, this study shows that hydrogen persulfide and hydrogen polysulfides act as potent radical-scavenging antioxidants and that, in addition to two-electron redox mechanisms, one electron redox reaction may also play important role in the in vivo defense against deleterious oxidative stress.

Effect of Magnesium Ion on the Radical-Scavenging Rate of Pterostilbene in an Aprotic Medium: Mechanistic Insight into the Antioxidative Reaction of Pterostilbene

Pterostilbene (PTS), a methylated analog of resveratrol (RSV), has recently attracted much attention due to its enhanced bioavailability compared to RSV. However, little is known about the radical-scavenging mechanism of PTS. In this study, we investigated the effect of Mg(ClO₄)₂ on the scavenging reaction of galvinoxyl radical (GO^•) by PTS in acetonitrile (MeCN). GO^• was used as a model for reactive oxygen radicals. The second-order rate constant (k_H) for the GO^•-scavenging reaction by PTS was more than threefold larger than that by RSV, although thermodynamic parameters, such as the relative O–H bond dissociation energies of the phenolic OH groups, ionization potentials, and HOMO energies calculated by the density functional theory are about the same between PTS and RSV. The oxidation peak potential of PTS determined by the cyclic voltammetry in MeCN (0.10 M Bu₄NClO₄) was also virtually the same as that of RSV. On the other hand, no effect of Mg (ClO₄)₂ on the k_H values was observed for PTS, in contrast to the case for RSV. A kinetic isotope effect of 3.4 was observed when PTS was replaced by a deuterated PTS. These results suggest that a one-step hydrogen-atom transfer from PTS to GO^• may be the rate-determining step in MeCN.

RP-HPLC-ESI-QTOF-MS Qualitative Profiling, Antioxidant, Anti-Enzymatic, Anti-Inflammatory, and Non-Cytotoxic Properties of Ephedra alata Monjauzeana

An investigation was conducted to study the beneficial effects of Ephedra alata monjauzeana crude extract (EamCE). The chemical profile was determined using RP-HPLC–ESI-QTOF-MS analysis, revealing the presence of twenty-one flavonoids and phenolic acids. A series of antioxidant assays was carried out using ten different methods. The EamCE has demonstrated a significant antioxidant potential, with interesting IC₅₀ values not exceeding 40 µg/mL in almost activities. Likewise, a significant inhibition of key enzymes, involved in some health issues, such as Alzheimer’s disease, diabetes, hyperpigmentation, dermatological disorders, gastric/urinary bacterial infections, and obesity, was observed for the first time. The IC₅₀ values ranged from 22.46 to 54.93. The anti-inflammatory and non-cytotoxic activities were assessed by heat-induced hemolysis and cell culture methods, respectively; the EamCE has shown a prominent effect in both tests, notably for the anti-inflammatory effect that was superior to the reference compound “diclofenac” (IC₅₀: 71.03 ± 1.38 > 70.23 ± 0.99 (µg/mL)). According to these results, this plant could be used in a large spectrum as a food supplement, as a natural remedy for various physiological disorders and pathologies; and it might serve as a preventive and health care agent.

Chemical Composition and Antioxidant, Anti-Inflammatory, and Enzyme Inhibitory Activities of an Endemic Species from Southern Algeria: Warionia saharae

Warionia saharae Benth. & Coss. (Asteraceae) is an endemic species of North Africa naturally grown in the southwest of the Algerian Sahara. In the present study, this species’ hydromethanolic leaf extract was investigated for its phenolic profile characterized by ultra-high-performance liquid chromatography coupled with a diode array detector and an electrospray mass spectrometer (UHPLC-DAD-ESI/MS). Additionally, the chemical composition of W. saharae was analyzed by gas chromatography–mass spectrometry, and its antioxidant potential was assessed through five in vitro tests: DPPH^● scavenging activity, ABTS^●+ scavenging assay, galvinoxyl scavenging activity, ferric reducing power (FRP), and cupric reducing antioxidant capacity. The UHPLC-DAD-ESI/MS analysis allowed the detection and quantification of 22 compounds, with taxifolin as the dominant compound. The GC–MS analysis allowed the identification of 37 compounds, and the antioxidant activity data indicate that W. saharae extract has a very high capacity to capture radicals due to its richness in compounds with antioxidant capacity. The extract also showed potent α-glucosidase inhibition as well as a good anti-inflammatory activity. However, weak anti-α-amylase and anticholinesterase activities were recorded. Moreover, an in silico docking study was performed to highlight possible interactions between three significant compounds identified in W. saharae extract and α-glucosidase enzyme.

Evaluation of the Free Radical Scavenging Activities of Ellagic Acid and Ellagic Acid Peracetate by EPR Spectrometry

The purpose of this study was to examine the free radical scavenging and antioxidant activities of ellagic acid (EA) and ellagic acid peracetate (EAPA) by measuring their reactions with the radicals, 2,2-diphenyl-1-picrylhydrazyl and galvinoxyl using EPR spectroscopy. We have also evaluated the influence of EA and EAPA on the ROS production in L-6 myoblasts and rat liver microsomal lipid peroxidation catalyzed by NADPH. The results obtained clearly indicated that EA has tremendous ability to scavenge free radicals, even at concentration of 1 µM. Interestingly even in the absence of esterase, EAPA, the acetylated product of EA, was also found to be a good scavenger but at a relatively slower rate. Kinetic studies revealed that both EA and EAPA have ability to scavenge free radicals at the concentrations of 1 µM over extended periods of time. In cellular systems, EA and EAPA were found to have similar potentials for the inhibition of ROS production in L-6 myoblasts and NADPH-dependent catalyzed microsomal lipid peroxidation.

Fiaud's Acid, a novel organocatalyst for diastereoselective bis α-aminophosphonates synthesis with in-vitro biological evaluation of antifungal, antioxidant and enzymes inhibition potential

(S, S)-1-hydroxy-1-oxo-2-c,5-t-diphenylphospholane or Fiaud's acid is used as a novel and effective chiral organocatalyst for bis α-aminophosphonates synthesis with excellent diastereoselectivity and yields within short reaction time. All synthesized bis α-aminophosphonates revealed a good to excellent antifungal capacity, where the six compounds 4a, 4b, 4e, 4h, 4k and 4l are the best fungicide inhibiting the growth of Fusarium oxysporumandBotrytis cinereaby 65% to 84% with IC₅₀ values <0.02 mg/mL. Similarly, these six products exhibited a strong antioxidant effect, whereas a low inhibition activity was obtained with both AChE and BChE. Furthermore, they displayed a very weak inhibitory activity against tyrosinase except for the compound4l.These findings suggest a possible use of these compounds as synthetic pesticides with less hazardous effects with antioxidant, and anti-tyrosinase properties.

Relationship between the radical-scavenging activity of selected flavonols and thermodynamic parameters calculated by density functional theory

The relationship between radical-scavenging rate constants (k) in an aprotic medium and thermodynamic parameters calculated by density functional theory (DFT) was investigated for 7 flavonols, which are myricetin (Myr), quercetin (Que), morin (Mor), kaempferol (Kae), 2'-methylquercetin (2'-MeQue), 5'-methylquercetin (5'-MeQue), and 2',5'-dimethylquercetin (Me₂Que). The k values were determined for the reaction between the flavonols and galvinoxyl radical used as a reactivity model of reactive oxygen species in deaerated acetonitrile at 298 K. The energy difference values (D _HT, HT: hydrogen transfer) between the flavonols and the corresponding radicals, which equal to the relative O-H bond dissociation energies of the OH groups in the flavonols and ionisation potentials (IP) were calculated by DFT at the B3LYP/6-31++G(d) level with C-PCM solvation model parameterised for acetonitrile. Among the 7 flavonols used in this study, calculated IP values of 4 flavonols exhibited a linear correlation with log k, suggesting that the radical-scavenging reaction of these flavonols may proceed via an electron transfer as the rate determining step.

In vitro study of disodium cromoglicate as a novel effective hydrotrope solvent for hypericin utilisation in photodynamic therapy

Hypericin (HY) is a naphthodianthrone that naturally occurs in Hypericum perforatum L. It is a promising photosensitiser used in photodynamic therapy for and diagnosis of oncological diseases. However, its hydrophobic character is an obstacle that has prevented its efficient use. The commonly used solvent, dimethyl sulfoxide (DMSO), is a controversial constituent of HY formulations and its use has been rejected by many researchers studying HY both in vitro and in vivo. In this study, we propose the utilisation of hydrotropy to solubilise HY in an aqueous environment. Cromolyn (DSCG) is a non-toxic, well-tolerated, antiallergic drug that has been employed in clinical practice since 1970, and in aqueous solution it acts as a hydrotrope. At a molecular ratio of 1:12,000 HY to DSCG, the compound is able to solubilise HY in aqueous environment. In an HT-29 cell suspension, DSCG (1.8 mmol L-1) considerably enhances the interaction between HY (150 nmol L-1) and HT-29 cells, which leads to an HY fluorescence emission increase with a half-time approximately 2 min compared to 29 min for samples that lack DSCG. Studies using HT-29 adenocarcinoma cells showed that DSCG at a given concentration significantly improved accumulation of HY within cells compared to DMSO (p < 0.05) despite the relative resistance of the HT-29 cell line to HY-PDT. Though no significant difference between total reactive oxygen species production was observed for photoactivated HY dissolved in DMSO and DSCG, significant singlet oxygen generation by photoactivated HY dissolved in a DSCG-containing water solution at the studied molecular ratio was confirmed. We also clarified that DSCG does not act as a scavenger of ABTS and galvinoxyl free radicals. The results from an MTT assay showed that DSCG also significantly enhanced the cytotoxicity of photoactivated HY compared to DMSO (p < 0.05). This study has demonstrated the ability of DSCG to act as a solvent of HY and enhance the effectiveness of HY-PDT compared to the commonly used organic solvent, DMSO.

Unique antioxidant effects of herbal leaf tea and stem tea from Moringa oleifera L. especially on superoxide anion radical generation systems

This study aimed to investigate the unique antioxidative effects of Japanese moringa products, herbal leaf tea and stem tea, using established free radical assays, focusing on superoxide anion (O₂^-) radical generation systems. Hot-water extracts from moringa teas resulted in different but lower scavenging activities than Trolox in four synthetic free radical models. Interestingly, these extracts further showed higher O₂^- radical scavenging effects than Trolox in the phenazine methosulfate-NADH-nitroblue tetrazolium and xanthine oxidase assay systems. Incubating human neutrophils in the presence of these tea extracts rather than Trolox effectively suppressed cellular O₂^- radical generation. Among the eight known phenolic constituents of moringa leaves, caffeic acid and chlorogenic acid may be responsible for the O₂^-specific radical scavenging capacity stronger than that of Trolox. These results suggest that moringa herbal teas are a good source of natural antioxidants for preventing O₂^- radical-mediated disorders. Abbreviations: O₂^-: superoxide anion; ROS: reactive oxygen species; H₂O₂: hydrogen peroxide; XOD: xanthine oxidase; DPPH: 1,1-diphenyl-2-picrylhydrazyl; ABTS⁺: 2,2'-azinobis(2-ethylbenzothiazoline-6-sulfonic acid) cation; CPZ⁺: chlorpromazine cation; PMS: phenazine methosulfate; NBT: nitroblue tetrazolium; PMA: phorbol 12-myristate 13-acetate.

Biologically and chemically important hydrazino-containing imidazolines as antioxidant agents

Biologically and chemically useful hydrazinoimidazolines were evaluated as antioxidant and antihaemolytic agents. 1,1-Diphenyl-2-picrylhydrazyl radical (DPPH^•), galvinoxyl radical (GOR), nitric oxide (NO) and hydrogen peroxide (H₂O₂) scavenging assays, ferric ions reducing power assay, and ex vivo model of rat erythrocytes exposed to 2,2'-azobis(2-methylpropionamidine)dihydrochloride (AAPH) or H₂O₂ were used. The most potent DPPH^• scavengers proved to be hydrazinoimidazolines 3, 2, and 4, revealing excellent antiradical effects - superior or comparable to that of all antioxidant standards used. Moreover, these molecules showed strong NO neutralising potencies - better to that of ascorbic acid (AA) (3), 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox) (3 and 2), butylated hydroxytoluene (BHT) (3 and 2), and butylated hydroxyanisole (BHA) (3, 2, and 4). Compound 4 was also effective in GOR scavenging. The excellent scavenger of GOR, NO, and H₂O₂ proved to be structure 5, with the potency superior or comparable to the majority of antioxidant standards used. In turn, compound 9 was effective in H₂O₂ and GOR neutralisation. All hydrazinoimidazolines revealed the reducing power that is higher than BHT. Moreover, the protective effects of most test compounds on oxidatively stressed erythrocytes were observed. Some structure-activity relationships were disclosed. A significance of the primary hydrazino group on antioxidant effects was confirmed. The most likely DPPH^• and GOR scavenging mechanisms for test compounds were propound. Among all the investigated molecules, hydrazinoimidazolines 5, 3, 2, 4, and 9, due to their excellent or good antiradical activities, can represent promising antioxidant candidates with prospective utility for prevention of diseases related to reactive oxygen/nitrogen species.

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

UPS, XPS and NEXAFS spectra of persistent free radical galvinoxyl are assigned using theoretical ΔDFT and TDDFT methods.

Antioxidant capacity of foods for scavenging reactive oxidants and inhibition of plasma lipid oxidation induced by multiple oxidants

Unregulated oxidation of biological molecules induced by multiple oxidants has been implicated in the pathogenesis of various diseases. Consequently, the effects of antioxidants contained in foods, beverages and supplements on the maintenance of health and prevention of diseases have attracted much attention of the public as well as scientists. However, recent human studies have shown inconsistent results and failed to demonstrate the beneficial effects of antioxidants. The mechanisms and dynamics of antioxidant action and assessment of antioxidant capacity have been the subject of extensive studies and arguments. In the present article, the antioxidant capacity has been reviewed focusing on two main issues: the capacity of antioxidants to scavenge multiple reactive oxidants and to inhibit plasma lipid oxidation induced by different biological oxidants. It is emphasized that the capacity of antioxidants to scavenge reactive oxidants does not always correlate linearly with the capacity to inhibit lipid oxidation and that it is necessary to specify the oxidant to assess the efficacy of antioxidants, since multiple oxidants contribute to oxidative damage in vivo and the effects of antioxidants depend on the nature of oxidants. A convenient and rapid method using a microplate reader is discussed for assessing the antioxidant capacity against plasma lipid oxidation induced by multiple oxidants including peroxyl radicals, peroxynitrite, hypochlorite, 15-lipoxygenase, and singlet oxygen.

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.

PRACTICAL APPLICATION

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.

Assessment of radical scavenging capacity of antioxidants contained in foods and beverages in plasma solution

Amount and rate of scavenging radical by antioxidants contained in foods and beverages are assessed in plasma solution.

Antioxidative properties of ascorbigen in using multiple antioxidant assays

The antioxidative properties of ascorbigen, one of the major indole-derived compounds of Brassica vegetables, were systematically evaluated using multiple assay systems with comparison to the well-known antioxidants ascorbic acid and Trolox. We first performed assays using model radicals, DPPH radical, galvinoxyl radical, and ABTS radical cation (ABTS(•+)). Ascorbigen showed stronger activity than that of ascorbic acid in the ABTS(•+)-scavenging assay but showed no activity in the DPPH radical- and galvinoxyl radical-scavenging assays. In the ABTS(•+)-scavenging assay, the indole moiety of ascorbigen contributed to scavenging of the radicals to produce indole-3-aldehyde as one of the final reaction products. The activity of ascorbigen was then evaluated by an oxygen radical absorbance capacity assay and an oxidative hemolysis inhibition assay using physiologically relevant peroxyl radicals, AAPH-derived radicals. Ascorbigen showed much stronger antioxidant activity than did ascorbic acid and Trolox. Therefore, antioxidant activity of ascorbigen might be more beneficial than has been thought for daily health care.

Protection of cells against oxidative stress by nanomolar levels of hydroxyflavones indicates a new type of intracellular antioxidant mechanism

Natural polyphenol compounds are often good antioxidants, but they also cause damage to cells through more or less specific interactions with proteins. To distinguish antioxidant activity from cytotoxic effects we have tested four structurally related hydroxyflavones (baicalein, mosloflavone, negletein, and 5,6-dihydroxyflavone) at very low and physiologically relevant levels, using two different cell lines, L-6 myoblasts and THP-1 monocytes. Measurements using intracellular fluorescent probes and electron paramagnetic resonance spectroscopy in combination with cytotoxicity assays showed strong antioxidant activities for baicalein and 5,6-dihydroxyflavone at picomolar concentrations, while 10 nM partially protected monocytes against the strong oxidative stress induced by 200 µM cumene hydroperoxide. Wide range dose-dependence curves were introduced to characterize and distinguish the mechanism and targets of different flavone antioxidants, and identify cytotoxic effects which only became detectable at micromolar concentrations. Analysis of these dose-dependence curves made it possible to exclude a protein-mediated antioxidant response, as well as a mechanism based on the simple stoichiometric scavenging of radicals. The results demonstrate that these flavones do not act on the same radicals as the flavonol quercetin. Considering the normal concentrations of all the endogenous antioxidants in cells, the addition of picomolar or nanomolar levels of these flavones should not be expected to produce any detectable increase in the total cellular antioxidant capacity. The significant intracellular antioxidant activity observed with 1 pM baicalein means that it must be scavenging radicals that for some reason are not eliminated by the endogenous antioxidants. The strong antioxidant effects found suggest these flavones, as well as quercetin and similar polyphenolic antioxidants, at physiologically relevant concentrations act as redox mediators to enable endogenous antioxidants to reach and scavenge different pools of otherwise inaccessible radicals.

Chaperone heat shock protein 90 mobilization and hydralazine cytoprotection against acrolein-induced carbonyl stress

Toxic carbonyls such as acrolein participate in many degenerative diseases. Although the nucleophilic vasodilatory drug hydralazine readily traps such species under "test-tube" conditions, whether these reactions adequately explain its efficacy in animal models of carbonyl-mediated disease is uncertain. We have previously shown that hydralazine attacks carbonyl-adducted proteins in an "adduct-trapping" reaction that appears to take precedence over direct "carbonyl-sequestering" reactions, but how this reaction conferred cytoprotection was unclear. This study explored the possibility that by increasing the bulkiness of acrolein-adducted proteins, adduct-trapping might alter the redistribution of chaperones to damaged cytoskeletal proteins that are known targets for acrolein. Using A549 lung adenocarcinoma cells, the levels of chaperones heat shock protein (Hsp) 40, Hsp70, Hsp90, and Hsp110 were measured in intermediate filament extracts prepared after a 3-h exposure to acrolein. Exposure to acrolein alone modestly increased the levels of all four chaperones. Coexposure to hydralazine (10-100 μM) strongly suppressed cell ATP loss while producing strong adduct-trapping in intermediate filaments. Most strikingly, hydralazine selectively boosted the levels of cytoskeletal-associated Hsp90, including a high-mass species that was sensitive to the Hsp90 inhibitor 17-N-allylamino-17-demethoxygeldanamycin. Biochemical fractionation of acrolein- and hydralazine-treated cells revealed that hydralazine likely promoted Hsp90 migration from cytosol into other subcellular compartments. A role for Hsp90 mobilization in cytoprotection was confirmed by the finding that brief heat shock treatment suppressed acute acrolein toxicity in A549 cells. Taken together, these findings suggest that by increasing the steric bulk of carbonyl-adducted proteins, adduct-trapping drugs trigger the intracellular mobilization of the key molecular chaperone Hsp90.

Antioxidant, antimicrobial and tyrosinase inhibitory activities of xanthones isolated from Artocarpus obtusus F.M. Jarrett

One of the most promising plants in biological screening test results of thirteen Artocarpus species was Artocarpus obtusus FM Jarrett and detailed phytochemical investigation of powdered dried bark of the plant has led to the isolation and identification of three xanthones; pyranocycloartobiloxanthone A (1), dihydroartoindonesianin C (2) and pyranocycloartobiloxanthone B (3). These compounds were screened for antioxidant, antimicrobial and tyrosinase inhibitory activities. Pyranocycloartobiloxanthone A (1) exhibited a strong free radical scavenger towards DPPH free radicals with IC₅₀ value of 2 µg/mL with prominent discoloration observed in comparison with standard ascorbic acid, α-tocopherol and quercetin, The compound also exhibited antibacterial activity against methicillin resistant Staphylococcus aureus (ATCC3359) and Bacillus subtilis (clinically isolated) with inhibition zone of 20 and 12 mm, respectively. However the other two xanthones were found to be inactive. For the tyrosinase inhibitory activity, again compound (1) displayed strong activity comparable with the standard kojic acid.

Reactivity toward oxygen radicals and antioxidant action of thiol compounds

Thiol compounds exert diverse functions in the defense network against oxidative stress in vivo. Above all, the role of glutathione in the enzymatic removal of hydrogen peroxide and lipid hydroperoxides has been well established. The scavenging of reactive free radicals is one of the many functions. In this study, the reactivities of several thiol compounds toward oxygen- and nitrogen-centered radicals were measured from their reaction with galvinoxyl and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radicals and also from their sparing effects on the decay of fluorescein, pyrogallol red, and BODIPY induced by peroxyl radicals. Furthermore, the antioxidant capacity against lipid peroxidation was assessed in the oxidation of methyl linoleate induced by free radicals in micelle systems. Cysteine, homocysteine, and glutathione exhibited considerable reactivity toward galvinoxyl, DPPH, and peroxyl radicals in this order but methionine did not. Bovine serum albumin (BSA) was less reactive toward these radicals than cysteine on molar base. Cysteine, homocysteine, and glutathione suppressed the oxidation of methyl linoleate in micelle systems, but methionine did not. The reactivity toward free radicals and antioxidant capacity of these thiol compounds were less than that of ascorbic acid, but higher than that of uric acid.

Intracellular ROS protection efficiency and free radical-scavenging activity of curcumin

Curcumin has many pharmaceutical applications, many of which arise from its potent antioxidant properties. The present research examined the antioxidant activities of curcumin in polar solvents by a comparative study using ESR, reduction of ferric iron in aqueous medium and intracellular ROS/toxicity assays. ESR data indicated that the steric hindrance among adjacent big size groups within a galvinoxyl molecule limited the curcumin to scavenge galvinoxyl radicals effectively, while curcumin showed a powerful capacity for scavenging intracellular smaller oxidative molecules such as H₂O₂, HO^•, ROO^•. Cell viability and ROS assays demonstrated that curcumin was able to penetrate into the polar medium inside the cells and to protect them against the highly toxic and lethal effects of cumene hydroperoxide. Curcumin also showed good electron-transfer capability, with greater activity than trolox in aqueous solution. Curcumin can readily transfer electron or easily donate H-atom from two phenolic sites to scavenge free radicals. The excellent electron transfer capability of curcumin is because of its unique structure and different functional groups, including a β-diketone and several π electrons that have the capacity to conjugate between two phenyl rings. Therfore, since curcumin is inherently a lipophilic compound, because of its superb intracellular ROS scavenging activity, it can be used as an effective antioxidant for ROS protection within the polar cytoplasm.

Isolation and analysis of bioactive constituents of sour cherry (Prunus cerasus) seed kernel: an emerging functional food

A plant-based diet reduces the risk for the development of several chronic diseases, such as ischemic heart disease or cancer due to natural compounds found in plants. Numerous cereals, berries, fruits, and vegetables, including sour cherry (Prunus cerasus), which is a favored fruit worldwide, contain biological active components. The antioxidant components of the sour cherry seed kernel have not been investigated until now. The aim of our study was to isolate and analyze the bioactive constituents of sour cherry seed kernel. We separated the oil fraction of the kernel; then the remaining solid fraction was dried, and the oil-free kernel extract was further analyzed. Our results show that sour cherry seed kernel oil contains vegetable oils including unsaturated fatty acids, oleic acids, alpha-tocopherol, tocotrienols, and tocopherol-like components. The components of the solid fraction include various bioactive structures such as polyphenols, flavonoids, vegetable acids, and pro- and anthocyanidins, which could have useful therapeutic effects in the prevention of various vascular diseases.

Antioxidant activity of 4-methylcoumarins

Polyphenolic coumarins are known to act as antioxidants in biological systems, but it is difficult to distinguish their antioxidant activity from the many other effects they produce in cells. We have determined the radical scavenging capacity of 22 structurally related natural and synthetic 4-methylcoumarins, by measuring their reaction with radicals, galvinoxyl and 2,2-diphenyl-1-picrylhydrazyl, using electron paramagnetic resonance spectroscopy. Efficient antioxidant activity of 4-methylcoumarins in cells was verified using the DCF fluorescent probe assay for determination of intracellular reactive oxygen species levels. As expected, the o-dihydroxysubstituted coumarins were found to be excellent radical scavengers and better than the m-dihydroxysubstituted or monohydroxysubstituted analogues, but surprisingly the corresponding o-diacetoxy derivatives also turned out to be good scavengers, even in the absence of an esterase. Another unexpected result was that the antioxidant efficiency of 4-methylcoumarins could be modulated by introducing an ethoxycarbonylethyl substituent at the C-3 position; this effect cannot be explained by simple electron donating/withdrawing properties. Coumarin concentrations of 10 microM or less were used in all experiments, corresponding to the levels relevant for therapeutic purposes. Considering that 4-methylcoumarins, in contrast to many other coumarins, are not metabolized to toxic epoxide intermediates, these results indicate promising new strategies for the design of non-toxic antioxidant coumarin-based drugs.

Characterization of the Radical-Scavenging Reaction of 2-O-Substituted Ascorbic Acid Derivatives, AA-2G, AA-2P, and AA-2S: A Kinetic and Stoichiometric Study

The aim of this study was to characterize the antioxidant activity of three ascorbic acid (AA) derivatives O-substituted at the C-2 position of AA: ascorbic acid 2-glucoside (AA-2G), ascorbic acid 2-phosphate (AA-2P), and ascorbic acid 2-sulfate (AA-2S). The radical-scavenging activities of these AA derivatives and some common low molecular-weight antioxidants such as uric acid or glutathione against 1,1-diphenyl-picrylhydrazyl (DPPH) radical, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS+), or galvinoxyl radical were kinetically and stoichiometrically evaluated under pH-controlled conditions. Those AA derivatives slowly and continuously reacted with DPPH radical and ABTS+, but not with galvinoxyl radical. They effectively reacted with DPPH radical under acidic conditions and with ABTS+ under neutral conditions. In contrast, AA immediately quenched all species of radicals tested at all pH values investigated. The reactivity of Trolox, a water-soluble vitamin E analogue, was comparable to that of AA in terms of kinetics and stoichiometrics. Uric acid and glutathione exhibited long-lasting radical-scavenging activity against these radicals under certain pH conditions. The radical-scavenging profiles of AA derivatives were closer to those of uric acid and glutathione rather than to that of AA. The number of radicals scavenged by one molecule of AA derivatives, uric acid, or glutathione was equal to or greater than that by AA or Trolox under the appropriate conditions. These data suggest the potential usage of AA derivatives as radical scavengers.

DISPOSITION AND METABOLISM OF [2-14C]QUERCETIN-4′-GLUCOSIDE IN RATS

Quercetin-4'-glucoside is a major flavonol in onions, and this study investigated the absorption and fate of radiolabeled quercetin-4'-glucoside in rats. Rats ingested [2-(14)C]quercetin-4'-glucoside and the distribution of radioactivity throughout the body was determined after 0.5, 1, 2, and 5 h. The gastrointestinal tract, liver, kidney, and plasma were extracted, and radiolabeled components were identified and quantified using high-performance liquid chromatography with on-line radioactivity detection and tandem mass spectrometry. Two hours after dosing, all the [2-(14)C]quercetin-4'-glucoside had been metabolized. More than 85% of the ingested radioactivity was present in the gastrointestinal tract at all time points with approximately 6% being absorbed and present in blood and internal organs, primarily the liver and kidneys. More than 95% of the absorbed radioactivity was in the form of >20 different methylated glucuronated and/or sulfated quercetin conjugates. Five hours after ingestion, the main radiolabeled metabolites were quercetin diglucuronides in the gut, liver, and kidneys and glucuronyl sulfates of methylated quercetin in plasma. The main site of quercetin metabolism seemed to be the gastrointestinal tract. Quercetin metabolites may have a major influence on the gut mucosal epithelium and on colonic disease.

Antioxidant action of a lipophilic nitroxyl radical, cyclohexane-1-spiro-2'-(4'-oxyimidazolidine-1'-oxyl) -5'-spiro-1"-cyclohexane, against lipid peroxidation under hypoxic conditions

Nitroxyl radicals are known to act as radical scavenging antioxidants. In the present study, a lipophilic nitroxyl radical, cyclohexane-1-spiro-2'-(4'-oxyimidazolidine-1'-oxyl)-5'-spiro-1"-cyclohexane (nitroxyl radical I) was synthesized and its antioxidant capacity was assessed in comparison with a hydrophilic nitroxyl radical, 4-hydroxy-2,2,6,6-tetra-methylpiperidine-N-oxyl (Tempol). Both nitroxyl radical I and Tempol inhibited methyl linoleate oxidation induced by free radicals, and the efficacy increased with decreasing partial pressure of oxygen, the effect being more pronounced for nitroxyl radical I than Tempol. Their hydroxylamines inhibited lipid peroxidation more effectively than their corresponding parent nitroxyl radicals. In liposomal membranes, a synergistic effect was observed in the combination of nitroxyl radical I with ascorbic acid, whereas only an additive effect was observed between Tempol and ascorbic acid. The present study suggests that nitroxyl radical I and its hydroxylamine may act as potent antioxidants, especially in combination with ascorbic acid under hypoxic conditions.