Antioxidant and Pro‐Oxidant Evaluation of a Potentilla alba L. Rhizome Extract

Using spectrophotometric methods, a H₂O‐soluble Potentilla alba L. rhizome extract was evaluated phytochemically, i.e., the total phenol, flavonoid, flavonol, flavanone, and proanthocyanidin contents were determined, and its antioxidant and pro‐oxidant properties, i.e., the Fe^III reductive and the Fe^II chelating properties, the 1,1‐diphenyl‐2‐picrylhydrazyl radical (DPPH^.), N,N‐dimethyl‐p‐phenylenediamine (DMPD^.+), and superoxide anion radical (O$\rm{{_{2}^{{^\cdot} -}}}$ )‐scavenging activities, the capacity to inhibit hydroxyl radical (HO^.)‐mediated deoxy‐D ‐ribose and phospholipid degradation, and the interaction with the Cu‐catalyzed HO^.‐mediated DNA degradation, were determined. The extract was found to contain a range of phenolic compounds recognized to possess strong antioxidant‐like properties. Moreover, the extract demonstrated dose‐dependent activities in all the antioxidant assays with the exception of the DNA‐degradation assay, where the components within the extract interfered with the assay components at concentrations ≥1.00 mg/ml. Potentilla species are known for their curative properties, with aerial/subterranean parts being prescribed for numerous indications. The data presented here suggests, though does not conclude, that the rhizomes contain compounds possessing a range of antioxidant‐related properties, which may underpin the therapeutic, viz., anti‐inflammatory and adaptogenic effects, ascribed to species of this genus.     

Antimutagenic and Antioxidant Potentials of Teucrium ramosissimum Essential Oil

The mutagenic and antimutagenic effects of the essential oil extracted from the aerial parts of Teucrium ramosissimum were evaluated by the bacterial reverse mutation assay in Salmonella typhimurium TA98, TA100, and TA1535, with and without exogenous metabolic activation (S9 fraction). The T. ramosissimum essential oil showed no mutagenic effect. In contrast, our results established that it possessed antimutagenic effects against sodium azide (SA), aflatoxin B1 (AFB1), benzo[a]pyrene (B[a]P), and 4‐nitro‐o‐phenylenediamine (NOPD). The antioxidant capacity of the tested essential oil was evaluated using enzymatic, i.e., the xanthine/xanthine oxidase (X/XOD) assay, and nonenzymatic systems, i.e., the nitro‐blue tetrazolium (NBT)/riboflavin and the DPPH assays. A moderate free radical‐scavenging activity was observed towards DPPH^. and O$\rm{{_{2}^{{^\cdot} -}}}$ . In contrast, T. ramosissimum essential oil showed no effect for all the tested concentrations in the X/XOD assay.     

Kinetic Modeling of Energy Metabolism and Superoxide Generation in Hepatocyte Mitochondria

Direct nonenzymatic oxidation of semiquinone by oxygen is one of the main sources of superoxide radicals in mitochondria. Using all the known data on hepatocyte mitochondria, we have revealed the correlation between the rate of superoxide generation by the bc ₁complex and the transmembrane potential (). Assuming that the main electrogenic stage of the Qcycle is the electron transfer between the cytochrome bhemes, then the rate of superoxide generation sharply increases when grows from 150 to 180 mV. However, this interrelation is ambiguous. Indeed, the increase of the generation rate with the growth of the potential can occur faster when succinate dehydrogenase is inhibited by malonate than when external ADP is exhausted. When the potential is changed by adding phosphate or potassium (K⁺), the rate of production remains constant, although the comparison of the rates at the same reveals the effect of phosphate or potassium. It turned out that the rate of generation is a function of rather than any of its components. Phosphate and K⁺have practically no influence on , since the change in is compensated by pH. The rate of superoxide generation by the bc ₁complex is a multiple function of the electron-transfer activity of enzymes, the processes determining the membrane potential (e.g., loading), and the oxygen concentration. The kinetic model proposed in this work may serve to understand how the superoxide production is regulated.     

Complexation of oxoanions and cationic metals by the biscatecholate siderophore azotochelin

Azotochelin is a biscatecholate siderophore produced by the nitrogen-fixing soil bacterium Azotobacter vinelandii. The complexation properties of azotochelin with a series of oxoanions [Mo(VI), W(VI) and V(V)] and divalent cations [Cu(II), Zn(II), Co(II) and Mn(II)] were investigated by potentiometry, UV–vis and X-ray spectroscopy. Azotochelin forms a strong 1:1 complex with molybdate (log K = 7.6 ± 0.4) and with tungstate and vanadate; the stability of the complexes increases in the order Mo < V < W (log K _app^Mo = 7.3 ± 0.4; log K _app^V = 8.8 ± 0.4 and log K _app^W = 9.0 ± 0.4 at pH 6.6). The Mo atom in the 1:1 Mo–azotochelin complex is bound to two oxo groups in a cis position and to the two catecholate groups of azotochelin, resulting in a slightly distorted octahedral configuration. Below pH 5, azotochelin appears to form polynuclear complexes with Mo in addition to the 1:1 complex. Azotochelin also forms strong complexes with divalent metals. Of the metals studied, Cu(II) binds most strongly to azotochelin , followed by Zn(II) , Mn(II) and Co(II) . Since very few organic ligands are known to bind strongly to oxoanions (and particularly molybdate) at circumneutral pH, the unusual properties of azotochelin may be used for the separation and concentration of oxoanions in the laboratory and in the field. In addition, azotochelin may prove useful for the investigation of the biogeochemistry of Mo, W and V in aquatic and terrestrial systems. Electronic supplementary material Supplementary material is available in the online version of this article at and is accessible for authorized users.     

Wild Sicilian Rosemary: Phytochemical and Morphological Screening and Antioxidant Activity Evaluation of Extracts and Essential Oils

To identify the best biotypes, an extensive survey of Sicilian wild rosemary was carried out by collecting 57 samples from various sites, followed by taxonomic characterization from an agronomic perspective. All the biotypes collected were classified as Rosmarinus officinalis L. A cluster analysis based on the morphological characteristics of the plants allowed the division of the biotypes into seven main groups, although the characteristics examined were found to be highly similar and not area‐dependent. Moreover, all samples were analyzed for their phytochemical content, applying an extraction protocol to obtain the nonvolatile components and hydrodistillation to collect the essential oils for the volatile components. The extracts were characterized by LC‐UV‐DAD/ESI‐MS, and the essential oils by GC‐FID and GC/MS analyses. In the nonvolatile fractions, 18 components were identified, namely, 13 flavones, two organic acids, and three diterpenes. In the volatile fractions, a total of 82 components were found, with as predominant components α‐pinene and camphene among the monoterpene hydrocarbons and 1,8‐cineole, camphor, borneol, and verbenone among the oxygenated monoterpenes. Cluster analyses were carried out on both phytochemical profiles, allowing the separation of the rosemary samples into different chemical groups. Finally, the total phenol content and the antioxidant activity of the essential oils and extracts were determined with the Folin–Ciocalteu (FC) colorimetric assay, the UV radiation‐induced peroxidation in liposomal membranes (UV‐IP test), and the scavenging activity of the superoxide radical (O$\rm{{_{2}^{{^\cdot} -}}}$ ). The present study confirmed that the essential oils and organic extracts of the Sicilian rosemary samples analyzed showed a considerable antioxidant/free radical‐scavenging activity.     

Garcimultiflorone G,a Novel Benzoylphloroglucinol Derivative from Garcinia multiflora with Inhibitory Activity on Neutrophil Pro‐Inflammatory Responses

A novel benzoylphloroglucinol derivative, garcimultiflorone G ( 1 ), was isolated from the fruits of Garcinia multiflora. The structure of 1 was determined through extensive 1D‐ and 2D‐NMR, and MS analyses. Garcimultiflorone G ( 1 ) showed inhibitory effects against superoxide anion (O$\rm{{_{2}^{{^\cdot} -}}}$ ) generation and elastase release by human neutrophils in response to formyl‐L ‐methionyl‐L ‐leucyl‐L ‐phenylalanine/cytochalasin B (fMLP/CB), with IC₅₀ values of 6.97±1.56 and 11.70±1.58 μM , respectively.     

Antioxidant Activities of Aqueous Extract from Agrimonia pilosa Ledeb and Its Fractions

Agrimonia pilosa Ledeb is used as the tonic for asthenia and fatigue in China. Considering that the energizing effect might be correlated with antioxidant properties, we investigated the antioxidant activities of aqueous extract (AE) from Agrimonia pilosa Ledeb by assessing radical‐scavenging and anti‐lipid‐peroxidation abilities. We found that AE shows a moderate antioxidant activity to scavenge DPPH^., O , and ^.OH and inhibit β‐carotene bleaching with IC₅₀ values of 13.0, 33.2, 351, and 11.9 μg/ml, respectively, while its AcOEt‐soluble fraction (ESF) and BuOH soluble fraction (BSF) exhibit remarkable efficiencies. The ESF's IC₅₀ values of scavenging DPPH^., O , and ^.OH, and inhibiting β‐carotene bleaching are 5.6, 5.8, 171, and 7.6 μg/ml, respectively, and those of BSF are 7.5, 8.4, 82.0, and 6.2 μg/ml, respectively. In addition, we found that there is a significant correlation between total phenol content and the antioxidant activity determined by O and ^.OH scavenging, and β‐carotene‐bleaching assays. Furthermore, HPLC analysis revealed the presence of quercetin, hyperoside, quercitrin, taxifoliol, luteolin‐7‐O‐β‐D ‐glucopyranoside, and rutin in Agrimonia pilosa Ledeb . Thus, we suggest that the extracts from Agrimonia pilosa Ledeb , could be considered as natural antioxidant sources and dietary nutritional supplements to prevent oxidation‐related diseases.     

Synthesis,Structure, DNA‐Binding Properties,and Cytotoxicity of Ruthenium(II) Polypyridyl Complexes

Many ruthenium(II) complexes show high antitumor activities, and the in vitro antitumor activities are usually related to DNA binding. We designed and synthesized two Ru^II polypyridyl complexes, [Ru(dmp)₂(fpp)]²⁺ (dmp=2,9‐dimethyl‐1,10‐phenanthroline; fpp=2‐[3,4‐(difluoromethylenedioxy)phenyl]imidazo[4,5‐f] [1,10]phenanthroline and [Ru(phen)₂(fpp)]²⁺ (phen=1,10‐phenanthroline). The DNA‐binding properties of these complexes have been investigated by spectroscopic titration, DNA melting experiments, viscosity measurements, and photoactivated cleavage. The mechanism studies of photocleavage revealed that singlet oxygen (¹O₂) and superoxide anion radical (O$\rm{{_{2}^{{^\cdot} -}}}$ ) may play an important role in the photocleavage. The cytotoxicity of complexes 1 and 2 have been evaluated by MTT (3‐(4,5‐dimethylthiazol‐2‐yl)‐2,5‐diphenyl‐2H‐tetrazolium bromide) method; complex 2 shows slightly higher anticancer potency than 1 does against all the cell lines screened.     

Energetics of the growth of Methanobacterium thermoautotrophicum and Methanococcus thermolithotrophicus on ammonium chloride and dinitrogen

Methanobacterium thermoautotrophicum was grown in continuous culture in a fermenter gassed with H₂ and CO₂ as sole carbon and energy sources, and in a medium which contained either NH₄Cl or gaseous N₂ as nitrogen source. Growth was possible with N₂. Steady states were obtained at various gas flow rates with NH₄Cl and with and the maintenance coefficient varied with the gas input and with the nitrogen source. Growth of Methanococcus thermolithotrophicus in continuous culture in a fermenter gassed with H₂, CO₂ as nitrogen, carbon and energy sources was also examined.Abbreviations molecular growth yield (g dry weight of cells per mol of CH₄ evolved) - growth rate (h^-1) - D dilution rate (h^-1) - rate (h_-1); relation of Neijssel and Tempest and of Stouthamer and Bettenhaussen - energy     

13C spin relaxation measurements in RNA: Sensitivity and resolution improvement using spin-state selective correlation experiments

A set of new NMR pulse sequences has been designed for the measurement of ¹³C relaxation rate constants in RNA and DNA bases: the spin-lattice relaxation rate constant R(C_z), the spin-spin relaxation rate constant R(C₊), and the CSA-dipolar cross-correlated relaxation rate constant . The use of spin-state selective correlation techniques provides increased sensitivity and spectral resolution. Sensitivity optimised C-C filters are included in the pulse schemes for the suppression of signals originating from undesired carbon isotopomers. The experiments are applied to a 15% ¹³C-labelled 33-mer RNA–theophylline complex. The measured ratios indicate that ¹³C CSA tensors do not vary significantly for the same type of carbon (C₂, C₆, C₈), but that they differ from one type to another. In addition, conformational exchange effects in the RNA bases are detected as a change in the relaxation decay of the narrow ¹³C doublet component when varying the spacing of a CPMG pulse train. This new approach allows the detection of small exchange effects with a higher precision compared to conventional techniques.     

Nitrogen sink strength of ectomycorrhizal morphotypes of <Emphasis Type="Italic">Quercus douglasii</Emphasis>, <Emphasis Type="Italic">Q. garryana</Emphasis>, and <Emphasis Type="Italic">Q. agrifolia</Emphasis> seedlings grown in a northern California oak woodland

Little information is known on what the magnitude of nitrogen (N) processed by ectomycorrhizal (ECM) fungal species in the field. In a common garden experiment performed in a northern California oak woodland, we investigated transfer of nitrogen applied as ¹⁵NH₄ or ¹⁵NO₃ from leaves to ectomycorrhizal roots of three oak species, Quercus agrifolia, Q. douglasii, and Q. garryana. Oak seedlings formed five common ectomycorrhizal morphotypes on root tips. Mycorrhizal tips were more enriched in ¹⁵N than fine roots. N transfer was greater to the less common morphotypes than to the more common types. ¹⁵N transfer from leaves to roots was greater when , not , was supplied. ¹⁵N transfer to roots was greater in seedlings of Q. agrifolia than in Q. douglasii and Q. garryana. Differential N transfer to ectomycorrhizal root tips suggests that ectomycorrhizal morphotypes can influence flows of N from leaves to roots and that mycorrhizal diversity may influence the total N requirement of plants.     

EPR evidence for generation of hydroxyl radical triggered byN-acetylchitooligosaccharide elicitor and a protein phosphatase inhibitor in suspension-cultured rice cells

Summary N-acetylchitooligosaccharides, fragments of the backbone of fungal cell wall, trigger rapid membrane responses such as transient depolarization, and elicit defense reactions including phytoalexin production in suspension-cultured rice cells. The generation of reactive oxygen species triggered by the oligosaccharide signal was analyzed with EPR spectroscopy using a spin trapping system, 4-pyridyl 1-oxideN-tert-butyl nitrone (4-POBN) and ethanol. OH generation was detected as the -hydroxyethyl adduct of 4-POBN after elicitation. Superoxide dismutase, catalase or diethylenetriamine pentaacetic acid, a metal chelator, inhibited generation, proposing the following reaction sequence: generation of in response to the oligosaccharide elicitor, followed by dismutation to H₂O₂, then generation of by the reaction of H₂O₂ with Fe²⁺ that is generated by the reduction of Fe³⁺ by . Generation of the same reactive oxygen species was also triggered by calyculin A, a protein phosphatase inhibitor, alone, suggesting the involvement of protein phosphorylation in its regulation during the oligosaccharide signal transduction.Abbreviations DMPO 5,5-dimethyl-1-pyrroline N-oxide - DTPA diethylenetriamine pentaacetic acid - 4-POBN 4-pyridyl 1-oxideN-tert-butylnitrone - SOD Superoxide dismutase - 4-hydroxy-TEMPO 2,2,6,6-tetramethyl-4-hydroxypiperidine-1-oxyl     

The regulation of K+ influx in excised barley roots

The electrochemical potential differences for potassium, between excised barley (Hordeum vulgare L.) roots and external media containing 0.05 mM KCl+0.5 mM CaSO₄, were determined over a 4-h period during which initially low-K⁺ roots accumulated K⁺ by pretreatment in 50 mM KCl plus 0.5 mM CaCl₂. This pretreatment resulted in increased internal [K⁺], decreased K⁺ influx (as measured from 0.05 mM KCl+0.5 mM CaSO₄) and decreased values of . These observations indicate that the decline of K⁺ influx associated with increased internal K⁺ concentration cannot be accounted for by passive adjustment to the electrochemical gradient for this ion.     

Effect of chlorogenic acid on hydroxyl radical

Chlorogenic acid (CGA) is considered to act as an antioxidant. However, the inhibitory effects of CGA on specific radical species are not well understood. Electron spin resonance (ESR) in combination with spin trapping techniques was utilized to detect free radicals. 5,5-Dimethyl-1-pyrroline-N-oxide (DMPO) was used as a spin trapping reagent while the Fenton reaction was used as a source of hydroxyl radical (·OH). We found that CGA scavenges ·OH in a dose-dependent manner. The kinetic parameters, IC₅₀ and V_max, for CGA scavenging of ·OH were 110 and 1.27 M/sec, respectively. The rate constant for the scavenging of ·OH by CGA was 7.73 × 10⁹ M^–1 sec^–1. Our studies suggest that the antioxidant properties of CGA may involve a direct scavenging effect of CGA on ·OH.     

Comparative ecophysiological effects of drought on seedlings of the Mediterranean water-saver Pinus halepensis and water-spenders Quercus coccifera and Quercus ilex

Ecophysiological and structural traits of seedlings of the water-saver Pinus halepensis and the water-spenders Quercus coccifera and Q. ilex were studied in response to water stress under greenhouse conditions. Water deficit reduced stomatal conductance (g _s) and, as a consequence, both net CO₂ assimilation (A) and transpiration rate (E) were also reduced. Water stress also emphasized midday down-regulation of the photochemical efficiency (dynamic photoinhibition) reducing quantum yield of noncyclic electron transport (Φ_PSII), photochemical quenching (qP) and photochemical efficiency of the open reaction centres of PSII () and involved an increase of thermal dissipation of excess energy. However, water stress not only induced dynamic photoinhibition but also brought a reduction in F _v/F _m (chronic photoinhibition). Despite the water-saving strategy of P. halepensis that limited net CO₂ assimilation, this species showed a higher photochemical efficiency and lower photoinhibition than Quercus species. This was not the result of a different photochemical quenching but was linked to a higher value of , indicating a less severe photo-inactivation of PSII. Water stress resulted in a loss of pigment content and in an increase of the carotenoids/chlorophyll ratio, antioxidant capacity and the biomass rate allocated to roots as opposed to that assigned to leaves. P. halepensis showed a lower photoinhibition and antioxidant activity than Quercus species due to its lower pigment content and higher proportion of carotenoids allowing P. halepensis to use, in a more effective way, the lesser excess energy absorbed.     

Theoretical study of AlH(2+)n (n=1-7) dications

The structures and stability of 1–7 dications were calculated at the ab initio MP2/aug-cc-pVTZ level of theory. The dications AlH²⁺ 1 and 2 were characterized to be unstable thermodynamically. However, these and the stable dications, 3–7 have considerable kinetic barriers for deprotonation. Each of the structures 3–7 contains one or more two-electron three-center (2e–3c) bonds. Aluminum atoms of these dications carry most of the positive charges, as indicated by NBO charge calculations.Dedicated to Professor Dr. Paul von Ragué Schleyer on the occasion of his 75th birthday     

The mechanism and kinetics of decomposition of 5-aminotetrazole

The pathway and ab initio direct kinetics of the decomposition 5-aminotetrazole (5-ATZ) to HN₃ and NH₂CN was investigated. Reactant, products and transition state were optimized with MP2 and B3LYP methods using 6–311G** and aug-cc-pVDZ basis sets. The intrinsic reaction coordinate curve of the reaction was calculated using the MP2 method with 6–311G** basis set. The energies were refined using CCSD(T)/6–311G**. Rate constants were evaluated by conventional transition-state theory (CVT) and canonical variational transition-state theory (TST), with tunneling effect over 300 to 2,500 K. The results indicated that the tunneling effect and the variational effect are small for the calculated rate constants. The fitted three-parameter expression calculated using the CVT and TST methods are and , respectively. Figure The mechanism of the decomposition process of 5-ATZ to HN₃ and NH₂CN     

Toxicity of oxygen from naturally occurring redox-active pro-oxidants

The survival of all aerobic life forms requires the ground-state of molecular oxygen, O₂. However, the activation of O₂ to reactive oxygen species (ROS) is responsible for universal toxicity. ROS are responsible in deleterious intracellular reactions associated with oxidative stress including membrane lipid peroxidation, and the oxidation of proteins and DNA. Redox-active allelochemicals such as quinones and phenolic compounds are involved in activating O₂ to its deleterious forms including superoxide anion free radical, $ {\rm O}_{\rm 2} ^{ \cdot - } $, hydrogen peroxide, H₂O₂, and hydroxyl radical, $ \cdot {\rm OH} $. Molecular oxygen is also activated in biologically relevant photosensitizing reactions to the singlet form, ¹O₂. The insect lifestyle exposes them to a broad diversity of pro-oxidant allelochemicals and, like mammalian species, they have developed an elaborate antioxidant system comprised of chemical antioxidants and a bank of antioxidant enzymes. We have found that an insect's antioxidant adaptation to a particular food correlates well with its risk of exposure to potential pro-oxidants. © 1995 Wiley-Liss, Inc.     

Retention of Dissolved Inorganic Nitrogen by Foliage and Twigs of Four Temperate Tree Species

Nitrogen (N) retention by tree canopies is believed to be an important process for tree nutrient uptake, and its quantification is a key issue in determining the impact of atmospheric N deposition on forest ecosystems. Due to dry deposition and retention by other canopy elements, the actual uptake and assimilation by the tree canopy is often obscured in throughfall studies. In this study, ¹⁵N-labeled solutions ( $ ^{15} {\text{NH}}_{4}^{ + } $ and $ ^{15} {\text{NO}}_{3}^{ - } $ ) were used to assess dissolved inorganic N retention by leaves/needles and twigs of European beech, pedunculate oak, silver birch, and Scots pine saplings. The effects of N form, tree species, leaf phenology, and applied $ {\text{NO}}_{3}^{ - } $ to $ {\text{NH}}_{4}^{ + } $ ratio on the N retention were assessed. Retention patterns were mainly determined by foliar uptake, except for Scots pine. In twigs, a small but significant ¹⁵N enrichment was detected for $ {\text{NH}}_{4}^{ + } $ , which was found to be mainly due to physicochemical adsorption to the woody plant surface. The mean $ {{^{15} {\text{NH}}_{4}^{ + } } \mathord{\left/ {\vphantom {{^{15} {\text{NH}}_{4}^{ + } } {^{15} {\text{NO}}_{3}^{ - } }}} \right. \kern-0em} {^{15} {\text{NO}}_{3}^{ - } }} $ retention ratio varied considerably among species and phenological stadia, which indicates that the use of a fixed ratio in the canopy budget model could lead to an over- or underestimation of the total N retention. In addition, throughfall water under each branch was collected and analyzed for $ ^{15} {\text{NH}}_{4}^{ + } $ , $ ^{15} {\text{NO}}_{3}^{ - } $ , and all major ions. Net throughfall of $ ^{15} {\text{NH}}_{4}^{ + } $ was, on average, 20 times higher than the actual retention of $ ^{15} {\text{NH}}_{4}^{ + } $ by the plant material. This difference in $ ^{15} {\text{NH}}_{4}^{ + } $ retention could not be attributed to pools and fluxes measured in this study. The retention of $ ^{15} {\text{NH}}_{4}^{ + } $ was correlated with the net throughfall of K⁺, Mg²⁺, Ca²⁺, and weak acids during leaf development and the fully leafed period, while no significant relationships were found for $ ^{15} {\text{NO}}_{3}^{ - } $ retention. This suggests that the main driving factors for $ {\text{NH}}_{4}^{ + } $ retention might be ion exchange processes during the start and middle of the growing season and passive diffusion at leaf senescence. Actual assimilation or abiotic uptake of N through leaves and twigs was small in this study, for example, 1–5% of the applied dissolved ¹⁵N, indicating that the impact of canopy N retention from wet deposition on forest productivity and carbon sequestration is likely limited.