Effect of phosphorus supply on the formation and function of proteoid roots of white lupin (Lupinus albus L.)

We investigated (1) the effect of constant and altered inorganic phosphate (P_i) supply (1–100 mmol m^–3) on proteoid root production by white lupin ( Lupinus albus L.); and (2) the variation in citrate efflux, enzyme activity and phosphate uptake along the proteoid root axis in solution culture. Proteoid root formation was greatest at P_i solution concentrations of 1–10 mmol m^–3 and was suppressed at 25 mmol m^–3 P_i and higher. Except at 1 mmol m^–3 P_i, the formation of proteoid roots did not affect plant dry matter yields or shoot to root dry matter ratios, indicating that proteoid roots can form under conditions of adequate P supply and not at the expense of dry matter production. Plants with over 50% of the root system as proteoid roots had tissue P concentrations considered adequate for maximum growth, providing additional evidence that proteoid roots can form on P-sufficient plants. There was an inverse relationship between the P_i concentration in the youngest mature leaf and proteoid root formation. Citrate efflux and the activities of enzymes associated with citric acid synthesis (phosphoenolpyruvate carboxylase and malate dehydrogenase) varied along the proteoid root axis, being greatest in young proteoid rootlets of the 1–3 cm region from the root tip. Citrate release from the 0–1 and 5–9 cm regions of the proteoid root was only 7% (per unit root length) of that from the 1–3 cm segment. Electrical potential and ³²P_i uptake measurements showed that P_i uptake was more uniform along the proteoid root than citrate efflux.     

Evaluation of antioxidant activity of <Emphasis Type="Italic">Melothria maderaspatana in vitro</Emphasis>

In this study, an aqueous extract of leaves from Melothria maderaspatana was tested for in vitro antioxidant activity. Free radical scavenging assays, such as hydroxyl radical, hydrogen peroxide, superoxide anion radical and 2,2-diphenyl-1-picryl hydrazyl (DPPH), 2,2’-azinobis-(3-ethyl-enzothiazoline-6-sulfonic acid) (ABTS) radical scavenging, and reducing power assay, were studied. The extract effectively scavenged hydroxyl radical, hydrogen peroxide and superoxide anion radicals. It also scavenged DPPH and ABTS radicals. Furthermore, it was found to have reducing power. All concentrations of leaf extract exhibited free radical scavenging and antioxidant power, and the preventive effects were in a dose-dependent manner. The antioxidant activities of the above were compared to standard antioxidants such as butylated hydroxytoluene (BHT), ascorbic acid, and α-tocopherol. The results obtained in the present study indicate that the M. maderaspatana extract could be considered a potential source of natural antioxidant.     

松栎柱锈菌春孢子多糖体外抗氧化活性

为了研究松栎柱锈菌（Cronartium orientale S.Kaneko）春孢子多糖的体外抗氧化活性,制备了该菌破壁春孢子精制多糖,并对所得春孢子多糖进行了总抗氧化能力、总还原力以及清除二苯代苦味酰基（DPPH·）、清除羟基自由基（·OH）、清除超氧阴离子（O₂^·）的活性进行了测定。体外抗氧化活性分析结果表明：松栎柱锈菌春孢子多糖具有较强的总抗氧化能力;虽然该菌多糖不具有清除多数氧自由基母体（O₂^·）的作用,也不具有清除人工合成自由基DPPH·的作用,但是其能够有效清除对机体破坏力最强的自由基·OH。这表明本文获得的松栎柱锈菌春孢子多糖具有对自由基选择性清除的能力,对其他自由基研究者具有参考价值,可为该菌的开发利用提供参考,也能够为森林有害生物开发利用提供理论依据。     

铁皮石斛化学成分及其抗氧化活性研究

采用硫酸-苯酚法、AlCl^₃比色法、酸性染料比色法测定铁皮石斛(Dendrobium officinale)花、叶、茎中多糖、黄酮、生物碱含量，通过DPPH和ABTS清除实验评价铁皮石斛花、叶、茎的水提物和乙醇提取物的体外抗氧化活性。结果表明，铁皮石斛不同部位的多糖含量茎>花>叶，黄酮含量花>叶>茎，生物碱在各个部位分布均较少。其中茎的多糖含量可达23.92%，花中黄酮含量可达1.847%。抗氧化能力评价表明，铁皮石斛花水提物、茎醇提物、花醇提物的DPPH自由基清除能力相对较好，半效应浓度(EC₅₀)分别为410.4 μg·mL^-1、454.1 μg·mL^-1、573.2 μg·mL^-1；铁皮石斛茎醇提物、花醇提物、花水提物ABTS自由基清除能力相对较好，半效应浓度(EC₅₀)分别为61.1 μg·mL^-1、62.2 μg·mL^-1、103.0 μg·mL^-1。铁皮石斛花的提取物抗氧化活性整体优于叶和茎，醇提物抗氧化能力优于水提物。     

香桃木叶片粗多酚抗氧化活性的研究

以香桃木叶片为材料,60%乙醇提取获得粗多酚样品,并对样品的油脂抗氧化性和自由基清除能力进行研究。结果表明,未经纯化的香桃木粗多酚对油脂抗氧化效果优于BHT和V_C等人工合成抗氧化剂;在清除自由基的实验中,相同浓度的香桃木粗多酚对DPPH自由基的清除率为V_E的5倍,对羟自由基的清除效果也略优于V_C。由此可以预见香桃木粗多酚在精细加工、经纯化后抗氧化效果会更加显著。     

Phytochemical analysis,antioxidant and antimicrobial activity of wild and in vitro derived plants of Ceropegia thwaitesii Hook – An endemic species from Western Ghats,India

Ceropegia thwaitesii Hook (Asclepiadaceae), an endemic plant species, due to habitat destruction and over exploitation has a very restricted distribution in the Western Ghats of Tamil Nadu, India. The present wrok aimed to determine the chemical composition, the total phenolic (TPC), flavonoid (TFC) and tannin content (TEC), and to assess the antioxidant properties of various extracts of in vivo plants (IVP) and in vitro regenerated plants (IRP) of C. thwaitesii. Some phenolic compounds like gallic acid, cathechol, vanillin and salicylic acid were identified and quantified by HPLC. All the extracts possessed relevant radical scavenging activity on DPPH, Superoxide radical scavenging activity, and Nitric oxide radicals as well as total antioxidant ability. DPPH assay of in vitro methanol stems extracts and ethanol leaves extracts revealed the best antioxidant properties with important IC₅₀ values of 0.248?±?0.45?µg/mL and 0.397?±?0.67?µg/mL, respectively, whereas in vivo chloroform stems extracts showed a lower antioxidant activity (IC₅₀ of 10.99?±?0.24?µg/mL). The IRP methanol extracts of stem and leaves had good inhibitory activity against all tested microorganisms in a dose-dependent manner. These results suggested that in vitro raised plants of C. thwaitesii are an excellent source of antioxidant compounds to be exploited on an industrial level as food additive.     

Antioxidant and Antimicrobial Activity in Some Indian Herbal Plants: Protective Effect against Free Radical Mediated DNA Damage

Indian herbal plant species Lantana indica, Adhatoda vasica, Pandanus furcatus, Tylophora indica and Centella asiatica, traditionally used in ethno medicines to treat common infections and various disorders, have been studied for their antimicrobial and antioxidant activity. The methanolic extracts of the plant leaves exhibited significant and dose-dependent antioxidant activities in DPPH radical scavenging, ferric ion reducing and phosphomolybdate assays. These leaf extracts showed antimicrobial activity against selected Gram +ve and Gram ?ve bacterial strains. A. vasica and L. indica extracts possessed maximum antioxidant and antimicrobial activity, respectively. The activities could be correlated to phenolics and flavonoid content of the leaf extracts which ranged from 30.25 to 91.98 mg GAE g^?1 dw leaf extract and 2.67 to 96.45 mg RE g^?1 dw leaf extract respectively. The aqueous extracts of plant leaves significantly protected the DNA damage against the oxidative damage caused by hydroxyl radicals.     

茶多糖的抗氧化活性及对细胞氧化损伤的保护机制

茶多糖是一种从茶叶中提取的酸性糖蛋白,具有良好的抗氧化活性。以自由基清除率为指标,分析皖西南地区夏秋茶多糖的抗氧化活性,基于H₂O₂和EDTA-Fe²⁺建立的外源性羟基自由基(·OH)损伤细胞模型和PMA诱导内源性羟基自由基损伤模型,进一步探讨茶多糖对自由基损伤的修复作用机制。结果表明,茶多糖具有良好的体外抗氧化活性,对DPPH·和·OH均具有较强的清除效果,EC₅₀值分别为209.5和535.2μg·mL^–1,最大清除效率与Vc相当。细胞增殖实验表明,外源性和内源性自由基氧化损伤模型中细胞存活率均随着茶多糖浓度的增加而升高,在茶多糖浓度为800μg·mL^–1时细胞存活率分别高达87.41%和85.84%,且显著高于模型组(47.67%和48.03%)。在修复机制上,利用激光共聚焦显微镜显影细胞内活性氧(ROS)分布以及荧光强度,分析结果显示,与模型组相比,茶多糖对于细胞模型中外源和内源性ROS均具有明显的清除效果,与体外抗氧化实验结果一致。茶多糖在体外表...     

球孢白僵菌不同菌株清除自由基活性评价

选择不同来源的12株球孢白僵菌,分别测定菌丝体2种溶剂提取物在不同抗氧化模型中的抗氧化作用。结果表明,不同溶剂提取物对二苯基苦味酰基苯肼自由基(DPPH)和羟自由基(.OH)均有清除作用,但是清除自由基的活性不同,乙酸乙酯提取物对.OH的清除作用最为显著,活性较高,最高清除率达到71.54%。甲醇提取物活性均较低,30 min时甲醇提取物对DPPH和.OH清除率最高分别为36%和38.96%,12株白僵菌间的清除自由基活性有较大的差异。     

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.     

Seasonal patterns in water, sodium and energy turnover in free-living echidnas, Tachyglossus aculeatus (Mammalia: Monotremata)

The energetics of an egg-laying mammal, the echidna ( Tachyglossus aculeatus ), were studied in the wild by means of isotope turnover techniques. Water and sodium influx rates were highest in summer (47.7±15.3 ml kg^-1 day^-1 and 1.20±0.52 mmol kg^-1 day^-1, respectively) and associated with high metabolic rates (0.509±0.048 ml CO₂ g^-1 h^-1). Water and sodium influxes and metabolic rates were lowest in May and June (7.8±6.4 ml H₂O kg^-1 day^-1, 0.21±0.12 mmol Na kg^-1 day^-1 and 0.205±0.129 ml CO₂ g^-1 h^-1, respectively). These low rates in late autumn/early winter are associated with reduced activity, the animals spending substantial periods of time in torpor. The comparatively low isotope turnover rates of echidnas are a consequence of their diet; ants and termites which have low mass-specific energy contents.     

Salinity stress constrains photosynthesis in Fraxinus ornus more when growing in partial shading than in full sunlight: consequences for the antioxidant defence system

Background and Aims

A major challenge in plant ecophysiology is understanding the effects of multiple sub-optimal environmental conditions on plant performance. In most Mediterranean areas soil salinity builds up during the summer because of low availability of soil water coupled with hot temperatures. Although sunlight and soil salinity may strongly interact in determining a plant''s performance, this has received relatively little attention.

Methods

Two-year-old seedlings of Fraxinus ornus were grown outdoors in pots during a Mediterranean summer in either 45 % (shaded plants) or 100 % (sun plants) sunlight irradiance and were supplied with either deionized water or deionized water plus 75 mm NaCl. Morpho-anatomical traits, water and ionic relations, gas exchange and photosystem II performance, concentrations of individual carotenoids, activity of antioxidant enzymes, concentrations of ascorbic acid and individual polyphenols were measured in leaves. Leaf oxidative stress and damage were estimated by in vivo analysis of stable free radicals and ultrastructural analyses.

Key Results

Leaf concentrations of potentially toxic ions did not markedly differ in shaded or sun plants in response to salinity. Leaves of sun plants displayed superior water use efficiency compared with leaves of shaded plants, irrespective of salinity treatment, and had both better stomatal control and higher CO₂ carboxylation efficiency than leaves of shaded plants. In the salt-treated groups, the adverse effects of excess midday irradiance were greater in shade than in sun plants. The activity of enzymes responsible for detoxifying hydrogen peroxide decreased in shaded plants and increased in sun plants as a result of salinity stress. In contrast, the activity of guaiacol peroxidase and the concentration of phenylpropanoids increased steeply in response to salinity in shaded plants but were unaffected in sun plants.

Conclusions

It is concluded that salinity may constrain the performance of plants growing under partial shading more severely than that of plants growing under full sun during summer. The results suggest co-ordination within the antioxidant defence network aimed at detoxifying salt-induced generation of reactive oxygen species.     

Antimicrobial activity and mechanism of action of Nu-3, a protonated modified nucleotide

For centuries, plants have been used in traditional medicines and there has been recent interest in the chemopreventive properties of compounds derived from plants. In the present study, we investigated the antibutyrylcholinestrasic (anti-BuChE) and antioxidant (against some free radicals) activities of extracts from Rhus pentaphyllum. Aqueous extracts were prepared from powdered R. pentaphyllum roots, leaves and seeds and characterized for the presence of tannins, flavonoids and coumarins. Seeds aqueous extract contained the highest quantities of both flavonoids and tannins (21.12% and 17.45% respectively). In the same way, seeds extracts displayed remarkable inhibition against BuChE over 95%, at 100 μg/ml and with IC₅₀ 0.74 μg/ml. In addition, compared to leaves and roots extracts, seeds aqueous extract revealed relatively strong antiradical activity towards the ABTS ^.+ (IC₅₀ = 0.25 μg/ml) and DPPH (IC₅₀ = 2.71 μg/ml) free radicals and decreased significantly the reactive oxygen species such O₂ ^.- (IC₅₀ = 2.9 μg/ml) formation evaluated by the non-enzymatic generating O₂ ^.- system (Nitroblue tetrazolium/riboflavine). These data suggest that the anti-BuChE activities mechanism of these extracts occurs through a free radical scavenging capacities. The present study indicates that extracts of Rhus pentaphyllum leaves, seeds and roots are a significant source of compounds, such as tannins, flavonoids and coumarins, with anti-BuChE and antioxidant activities, and thus may be useful for chemoprevention.     

Free radical generation and antioxidant content in chloroplasts from soybean leaves exposed to ultraviolet-B

The aim of this work was to study the effect of ultraviolet-B (UV-B) exposure on oxidative status in chloroplasts isolated from soybean ( Glycine max cv . Hood). Chloroplasts were isolated from soybean leaves excised from either control seedlings or those exposed to 30 and 60 kJ m⁻² day⁻¹ of UV-B radiation for 4 days. Chloroplastic oxidative conditions were assessed as carbon-centered radical, carbonyl groups and ascorbyl radical content. Treatment with UV-B increased the carbon-centered radical-dependent EPR signal significantly by 55 and 100% in chloroplasts from leaves exposed to 30 and 60 kJ m⁻² day⁻¹ UV-B, respectively, compared to radical content in chloroplasts from control leaves. The content of carbonyl groups increased by 37 and 62% in chloroplasts isolated from soybean leaves irradiated for 4 days with 30 and 60 kJ m⁻² day⁻¹ UV-B, respectively. The content of soluble metabolites in isolated chloroplasts should not be taken as absolute in vivo values; however, these data are valuable for comparative studies. UV-B exposure did not significantly affect ascorbyl radical content compared to controls. The content of ascorbic acid and thiols in chloroplasts isolated from leaves exposed to 60 kJ m⁻² day⁻¹ UV-B was increased by 117 and 20.8%, respectively, compared to controls. Neither the content of total carotene nor that of β -carotene or α -tocopherol was affected by the irradiation. The results presented here suggest that the increased content of lipid radicals and oxidized proteins in the chloroplasts isolated from leaves exposed to UV-B could be ascribed to both the lack of antioxidant response in the lipid soluble fraction and the modest increase in the soluble antioxidant content.     

Non-photosynthetic mechanisms of growth reduction in pea (Pisum sativum L.) exposed to UV-B radiation

Pisum sativum cv. Guido grown under controlled environment conditions was exposed to either low or high UV-B radiation (2·2 or 9·9 kJ m^–2 d^–1 plant-weighted UV-B, respectively). Low or high UV-B was maintained throughout growth (LL and HH treatments, respectively) or plants were transferred between treatments when 22 d old (giving LH and HL treatments). High UV-B significantly reduced plant dry weight and significantly altered plant morphology. The growth and morphology of plants transferred from low to high UV-B were little affected, when compared with those of LL plants. By contrast, plants moved from high to low UV-B showed marked increases in growth when compared with HH plants. This contrast between HL and LH appeared to be related to the effect of UV-B on plant development. Exposure to high UV-B throughout development consistently reduced leaf areas. In fully expanded leaves there was no significant UV-B effect on cell area and reduced leaf area could be attributed to reduced cell number, suggesting effects on leaf primordia. Further reductions in the leaf area of younger leaves were the result of the slower development rate of plants grown at high UV-B, which also resulted in significant reductions in leaf number.     

Identification of chemical structure and free radical scavenging activity of diphlorethohydroxycarmalol isolated from a brown alga, Ishige okamurae

To obtain a natural antioxidant from a marine biomass, this study investigated the antioxidative activity of methanolic extracts from the marine brown alga, Ishige okamurae collected off Jeju Island. A potent free radical scavenging activity was detected in the ethyl acetate fraction containing polyphenolic compounds, and the potent antioxidant elucidated as a kind of phlorotannin, diphlorethohydroxycarmalol, by NMR and mass spectroscopic data. The free radical scavenging activities of the diphlorethohydroxycarmalol were investigated in relation to 1,1-diphenyl-2-picrylhydrazyl (DPPH), alkyl, and hydroxyl radicals using an electron spin resonance (ESR) system. The diphlorethohydroxycarmalol was found to scavenge DPPH (IC50=3.41 microM) and alkyl (IC50=4.92 microM) radicals more effectively than the commercial antioxidant, ascorbic acid. Therefore, these results present diphlorethohydroxycarmalol as a new phlorotannin with a potent antioxidative activity that could be useful in cosmetics, foods, and pharmaceuticals.     

Symbiotic N2 fixation in a high Alpine grassland: effects of four growing seasons of elevated CO2

1. Increasing carbon dioxide concentration (E: 680 μl CO₂ litre^–1 vs ambient, A: 355 μl CO₂ litre^–1) around late-successional Alpine sedge communities of the Swiss Central Alps (2450 m) for four growing seasons (1992–1995) had no detectable effect on symbiotic N₂ fixation in Trifolium alpinum —the sole N₂-fixing plant species in these communities (74 ± 30 mg N m^–2 year^–1, A and E plots pooled).
2. This result is based on data collected in the fourth growing season showing that elevated CO₂ had no effect on Trifolium above-ground biomass (4·4 ± 1·7 g m^–2, A and E plots pooled, n = 24) or N content per unit land area (124 ± 51 mg N m^–2, A and E pooled), or on the percentage of N Trifolium derived from the atmosphere through symbiotic N₂ fixation (%Ndfa: 61·0 ± 4·1 across A and E plots) estimated using the ¹⁵N dilution method.
3. Thus, it appears that N inputs to this ecosystem via symbiotic N₂ fixation will not be dramatically affected in the foreseeable future even as atmospheric CO₂ continues to rise.     

The effects of light on induction, time courses, and kinetic patterns of net nitrate uptake in barley

Barley seedlings ( Hordeum vulgare L.) were grown hydroponically with (induced) or without (uninduced) nitrate in a light/dark cycle with high photon flux density to determine the effects of light on time courses, induction and kinetics of net nitrate uptake. Nitrate uptake was induced by external nitrate in both light and dark and was prevented by 1 mol m^–3 p-fluorophenylalanine. In high light, nitrate uptake was about 2-fold higher than in low light. During time course experiments the uptake rates oscillated due to daily light–dark changes. Rates of nitrate uptake also increased at about 2200 h during continuous darkness. This increase coincided approximately with the time at which the dark period started during the previous culture of the plants, indicating that it was due to a mechanism associated with an endogenous diurnal rhythm. When calculating the kinetics of nitrate uptake, a model with two saturable systems, including a high-affinity system (HATS) and a low-affinity system (LATS), gave the best fit to data in all treatments. The apparent affinity of the HATS ranged from 7·7 to 12·2 mmol m^–3 in induced plants in all light conditions. The effect of light on the HATS was mainly an increase of apparent V _max in the step from low to high light. In uninduced plants the HATS operated at a very low activity which was strongly enhanced during induction. Interpretation of the calculated kinetics of the LATS was much more difficult on the basis of net uptake data. The apparent affinity of the LATS increased from 24·3 mol m^–3 in low light up to 0·17 mol m^–3 after acceleration in high light. These extreme changes in apparent affinity of the LATS could not be explained satisfactorily, and the nature of this system is also discussed with respect to the method used.     

Spatio-temporal variation in macroinvertebrate assemblages of glacial streams in the Swiss Alps

1. Changes in water chemistry, benthic organic matter (BOM), and macroinvertebrates were examined in four different glacial streams over an annual cycle. The streams experienced strong seasonal changes in water chemistry that reflected temporal changes in the influence from the source glacier, especially in water turbidity, particulate phosphorus and conductivity.
2. Nitrogen concentrations were high (nitrate-N values were 130–274 μg L^–1), especially during spring snowmelt runoff. Benthic organic matter attained >600 g m^–2 dry mass at certain times, peaks being associated with seasonal blooms of the alga Hydrurus foetidus .
3. Macroinvertebrate taxon richness was two to three times higher (also numbers and biomass) in winter than summer suggesting winter may be a more favourable period for these animals. Benthic densities averaged 1140–3820 ind. m^–2, although peaking as high as 9000 ind. m^–2. Average annual biomass ranged from 102 to 721 mg m^–2, and reached >2000 mg m^–2 at one site in autumn.
4. Taxa common to all sites included the dipterans Diamesa spp. and Rhypholophus sp., the plecopterans Leuctra spp. and Rhabdiopteryx alpina , and the ephemeropterans Baetis alpinus and Rhithrogena spp. Principal components analysis clearly separated winter assemblages from those found in summer.     

蔷薇科一些植物鲜叶提取物清除DPPH自由基活性的研究

用二苯基苦基苯肼自由基酶标仪法, 对亚热带蔷薇科常见的50种木本植物鲜叶的自由基清除活性进行了比较,发现不同属、不同种树木鲜叶的80%甲醇提取物的自由基清除活性有很大差异, 其中苹果属5种植物在相当于鲜叶浓度为0.5 mg/mL于37℃下孵育20 min时, 对0.5 mmol.L-1 DPPH自由基平均清除率达62.4%,而绣线菊属3种植物的平均自由基清除率仅11.6%。尖嘴林檎、棣棠、木瓜、三叶海棠、湖北海棠、木香花、小果蔷薇和黄山花楸等鲜叶有较强的自由基清除活性,它们在浓度为0.5 mg/mL时的自由基清除率分别可达85.0%、75.8%、70.7%、69.6%、64.5%、62.5%、61.8%和61.3%,显示其有较大的开发潜力。