Herbicidal activity of the antibiotics geldanamycin and nigericin

Geldanamycin and nigericin, phytotoxic metabolites from a strain ofStreptomyces hygroscopicus, were tested for herbicidal activity and selectivity on a range of crop and weed species. In petri dish bioassays, geldanamycin reduced radicle growth of all species tested, whereas nigericin inhibited 7 of 10. The two compounds in mixture appeared to be additive rather than synergistic in effect. In assays with seeds and seedlings in field soil, geldanamycin showed significant preemergence activity on proso millet, barnyardgrass, garden cress, and giant foxtail. It had no postemergence herbicidal effect on any of the species tested. Nigericin had preemergence activity on garden cress and large crabgrass and postemergence activity on garden cress and velvetleaf. The postemergence effect of nigericin on velvetleaf was especially striking, with leaves showing symptoms of injury within 24–48 h of treatment. Doses as low as 0.3 kg/ha caused damage. The primary herbicidal effect of both compounds was slowing of seed germination or seedling growth, although some plants were killed, especially at higher rates of application. Herbicidal effects were most pronounced for 1 to 2 weeks after treatment and diminished thereafter.Michigan Agricultural Experiment Station journal article no. 13012.     

ALLELOPATHIC AND HERBICIDAL EFFECTS OF EXTRACTS FROM TREE OF HEAVEN (AILANTHUS ALTISSIMA)

Mature trees of Ailanthus altissima produce one or more potent inhibitors of seed germination and seedling growth. Inhibitor activity is highest in bark, especially of roots, intermediate in leaflets, and low in wood. Crude extracts of Ailanthus root bark and leaflets corresponding to 34 and 119 mg water extractable material/L, respectively, caused 50% inhibition of cress radicle growth. Ailanthus seeds also contain one or more inhibitors. These are bound within the seed by the pericarp but diffuse into water agar when the pericarp is removed. The inhibitor(s) could readily be extracted from Ailanthus tissues with methanol, but not dichloromethane, indicating polar characteristics. Ailanthus leaflets had highest inhibitory activity during expansion in spring, whereas activity of trunk bark peaked just before emergence of leaves. This pattern suggests transport of allelochemicals from bark into new leaves. A comparison of seven plant species for sensitivity to the inhibitor(s) from Ailanthus root bark showed little selectivity, although velvetleaf was somewhat more resistant. The inhibitor(s) from Ailanthus root bark exhibited strong herbicidal effects when sprayed pre- and postemergence on plants in soil in the greenhouse. Postemergence effects were striking, with nearly complete mortality of all species, except velvetleaf, at even the lowest doses tested. The results suggest the allelochemical(s) from Ailanthus may have potential for development as natural-product herbicides.     

Identification of an allelopathic compound from Ailanthus altissima (Simaroubaceae) and characterization of its herbicidal activity

Aqueous extracts of Ailanthus altissima bark and foliage were previously shown to be toxic to other plants. Using bioassay-directed fractionation, I isolated the phytotoxic compound from A. altissima root bark and identified it to be ailanthone, a quassinoid compound having molecular mass of 376. Ailanthone was highly phytotoxic, with concentrations of 0.7 ml/L causing 50% inhibition of radicle elongation in a standardized bioassay with garden cress (Lepidium sativum) seeds. Ailanthone exhibited potent pre- and postemergence herbicidal activity in greenhouse trials. Postcmergence activity was especially striking; even the lowest application rate (0.5 kg/ha) caused complete mortality of five of the seven plant species tested within 5 d of treatment. In contrast, the highest application rate (8 kg/ha) did not cause any detectable injury to A. altissima seedlings, indicating the presence of a protective mechanism in the producer species to prevent autotoxicity. Ailanthone was rapidly detoxified in field soil as a result of microbial activity. Applications of ailanthone equivalent to 0.5 and 4.0 kg/ha completely lost their phytotoxicity within ≤5 d when incubated in the presence of nonsterile soil. When incubated with sterile soil under identical conditions, however, ailanthone remained highly phytotoxic throughout the 21-d duration of the investigation. The high level of postemergence herbicidal activity in conjunction with its rapid biodegradation in soil suggest ailanthone may have potential for development as a natural-product herbicide.     

Herbicidal Derivatives of Aminomethylenebisphosphonic Acid. Part III. Structure—Activity Relationship

Derivatives of aminomethylenebisphosphonic acids constitute a class of promising herbicides. More than 40 N-substituted aminomethylenephosphonic acids were synthesized and evaluated for their herbicidal activity on common cress (Lepidium sativum L.) and cucumber (Cucumis sativus L.). Some of the tested compounds were found to exhibit strong herbicidal properties being equal in activity with the popular herbicide glyphosate as well as parent N-pyridylaminomethylenephosphonic acids. N-Substituted iminodi(methylenephosphonic) acids, which may be considered as close analog of glyphosate, were inactive toward test plants. Received October 25, 1996; accepted May 9, 1997     

Trace metal uptake by garden herbs and vegetables

In many regions of Iran, crops are irrigated with municipal and industrial wastewater that contain a variety of metals. The purpose of this study was to simulate the level of metals that may be presented to plants over a growing season in a controlled laboratory setting. Cadmium, lead, arsenic, chromium, mercury, nickel, copper, zinc, and selenium were applied to plants at the high rate of 200 g metal/ha/wk. The following plants were examined for metal accumulation and effects on yield: garden cress (Lipidium sativum), leek (Allium porrum L.), basil (Ocimum basilicum L.), mint (Mentha arvensis L.), onion (Allium capa L.), radish (Raphanus sativus L.), and tarragon (Artemisia draculus L.). All plants showed significant uptake of all metals when compared to control (p=0.05), and growth was significantly reduced (p=0.05). Cadmium and chromium levels of 85±7.4 and 47.6±8.9 μg/g); selenium levels were highest in tarragon (16.5±5.8 μg/g). Zinc levels were similar (p=0.05) in all species tested, as were mercury and lead. The remaining metals (nickel and copper) showed significant differences in uptake, depending on plant species.     

Drosophila alcohol dehydrogenase: Developmental studies on cryptic variant lines

Thirty-five cryptic variant lines were used to examine the mechanisms involved in genetic modulation of alcohol metabolism in Drosophila. Late third-instar larval, preemergence pupal, and adult stages cultured at 18 and 28 C were examined. Spectrophotometric analyses for native alcohol dehydrogenase (ADH) activity and residual ADH activity after treatment with guanidine hydrochloride and heat were performed. Differential response of cryptic variants to treatment with the denaturants during development suggested that this variation may have an adaptive significance.     

Isolation and identification of a plant growth inhibitor from Tinospora tuberculata Beumee

Tinospora tuberculata Beumee has been used widely as a folk medicine and several bioactive compounds have been isolated. However, no herbicidal compound has been reported in this species. Therefore, we investigated the presence of phytotoxins in T. tuberculata. The aqueous methanol extracts of T. tuberculata inhibited the growth of roots and shoots of cress (Lepidum sativum L.), lettuce (Lactuca sativa L.), timothy (Phleum pratense L.) and barnyard grass (Echinochloa crus-galli (L.) Beauv.). The extract was then purified by several chromatographic runs with monitoring the inhibitory activity and the main phytotoxic substance was isolated. The chemical structure of the compound was determined by spectral data as syringin (4-[(1E)-3-Hydroxyprop-1-en-1-yl]-2,6-dimethoxyphenyl β-d-glucopyranoside). It inhibited the root and shoot growth of all test plant species at concentrations >10 µM. The concentrations required for 50 % inhibition of root and shoot growth of cress and lettuce ranged from 78.2 to 412 μM, and that of timothy and barnyard grass renged from 9.8 to 73.2 µM. Effectiveness of syringin on monocotyledonous (timothy and barnyard grass) plants was greater than that on dicotyledonous (cress and lettuce) plants. These results suggest that syringin may contribute to the allelopathic effect caused by the T. tuberculata extract.     

Calcium-independent uncoupling activity of palmitic acid in liver mitochondria is regulated by the ion fluxes causing the interconversion of Δψ and ΔpH across the inner membrane

The effect of ion fluxes across the inner membrane on calcium-independent uncoupling activity of palmitic acid was investigated in experiments on rat liver mitochondria energized by the oxidation of succinate. The following compounds were used as the inductors of ion fluxes: the K⁺/H⁺ antiporter nigericin causing transformation of ΔpH into electrical potential difference (Δψ) across the inner membrane; tetraphenylphosphonium (TPP⁺) that freely crosses phospholipid membranes; protonophore carbonyl cyanide 4-(trifluoromethoxy)phenylhydrazone (FCCP) that induces a flow of H⁺ from the intermembrane space into the matrix and reduces Δψ and ΔpH. It was found that nigericin at a concentration of 20 nM, which causes an increase in maximal Δψ, partially inhibits the ability of palmitic acid to reduce Δψ and stimulates mitochondrial respiration. A specific inhibitor of the ATP/ADP antiporter (carboxyatractylate) and a substrate of the aspartate/glutamate antiporter (glutamate) increase Δψ and partially inhibit mitochondrial respiration in the presence of palmitic acid. Under these conditions, 10 μM cyclosporin A also inhibits respiration but has no effect on Δψ. The specific uncoupling activity of palmitic acid (V _U) and its specific components that characterize participation of the ATP/ADP antiporter (V _Catr), aspartate/glutamate antiporter (V _Glu), and cyclosporin-A-sensitive system (V _CsA) in the palmitic acid-induced uncoupling were estimated. It was shown that nigericin substantially reduces V _U, V _Catr and V _Glu but increases V _CsA. TPP⁺ at a concentration of 20 μM increases V _U and V _Glu, does not affect V _Catr and reduces V _CsA. FCCP at concentrations of 20 and 40 nM reduces Δψ by not more than 17% but does not affect V _U, V _Catr, V _Glu and V _CsA. The results suggest that the calcium-independent uncoupling effect of palmitic acid in liver mitochondria is caused by the return of protons to the matrix with participation of ADP/ATP and aspartate/glutamate antiporters and owing to activation of cyclosporin A-sensitive electron transport along the respiratory chain without affecting Δψ. The induced ion fluxes across the inner mitochondrial membrane can be considered as a factor of the calcium-independent regulation of uncoupling activity of palmitic acid in liver mitochondria with participation of the ADP/ATP and aspartate/glutamate antiporters and of the cyclosporin A-sensitive electron transport system.     

Allelopathy is involved in the formation of pure colonies of the fern Gleichenia japonica

The fern Gleichenia japonica is one of the most widely distributed fern and occurs throughout East to South Asia. The species often dominates plant communities by forming large monospecific colonies. However, the potential mechanism for this domination has not yet been described. The objective of this study was to test the hypothesis that allelochemicals are involved in the formation of G. japonica colonies. An aqueous methanol extract of G. japonica inhibited the growth of seedlings of garden cress (Lepidium sativum), lettuce (Lactuca sativa), ryegrass (Lolium multiflorum) and timothy (Phleum pratense). Increasing extract concentration increased the inhibition. These results suggest that G. japonica contain allelopathic substances. The extract was then purified by several chromatographies with monitoring the inhibitory activity and two growth inhibitory substances causing the allelopathic effect were isolated. The chemical structures of the two substances were determined by spectral data to be a novel compound 3-O-β-allopyranosyl-13-O-β-fucopyranosyl-3β-hydroxymanool (1) and 18-O-α-l-rhamnopyranosyl-(1→2)-β-d-glucopyranosyl-13-epitorreferol (2). These compounds inhibited the shoot and root growth of garden cress, lettuce, alfalfa (Medicago sativa), timothy, ryegrass and barnyardgrass (Echinochloa crus-galli) at concentrations greater than 0.1–1.0 mM. The concentrations required for 50% growth inhibition of root and shoot growth of these test plants ranged from 0.72 to 3.49 mM and 0.79 to 3.51 mM for compounds 1 and 2, respectively. Concentration of compounds 1 and 2 in soil under the pure colony of G. japonica was 4.9 and 5.7 mM, respectively, indicating concentrations over those required for 50% growth inhibition are potentially available under monocultural stands of these ferns. Therefore, these compounds may contribute to the allelopathic effects caused by presence of G. japonica and may thus contribute to the establishment of monocultural stands by this fern.     

Antimicrobial activity of some Indian plants

Antimicrobial activity of 105 Indian plant species was tested. Among them, 30 showed antibacterial activity; 20 of these exhibited antifungal action as well. Seeds ofCarum copticum, stem ofPinus longifolia, roots ofPlumbago zeylanica andSaussurea lappa, and rhizome ofAlpinia officinarum have considerable antifungal activity, especially against pathogenic fungi. Antibiotic activity against a wide variety of microorganisms—pathogenic and nonpathogenic gram-positive and gram-negative bacteria, yeast, and fungi—was also noted with leaves ofLawsonia inermis, roots ofPlumbago zeylanica, and fruits ofTamarindus indica,Terminalia belerica, andEmblica officinalis.     

Contact toxicity of some chemical and biological pesticides to several insect parasitoids and predators

Eight pesticides; methyl parathion, malathion (organo-phosphates), toxaphene (chlorinated hydrocarbon), carbaryl (carbamate), pyrethrin (plant derivative),Bacillus thuringiensis, nuclear polyhedrosis virus (Heliothis) (microbial insecticides), and 2,4-DB (postemergence herbicide) were evaluated at the minimum recommended field dose and reduced dosages for contact toxicity toBrachymeria intermedia (Hymenoptera: Chalcididae), Campoletis sonorensis (Hymenoptera: Ichneumonidae), Chelonus blackburni (Hymenoptera: Braconidae), Meteorus leviventris (Braconidae), Voria ruralis (Diptera: tachninidae), Chrysopa carnea (Neuroptera: Chrysopidae), andHippodamia convergens (Coleoptera: Coccinellidae). At minimum field dosages, percent mortality of parasitoids and predators was>27%, for the chemical insecticides. Mortality from pyrethrin was <31%, in all cases and 0% for 5 of the 8 species tested. Mortality of parasitoids and predators exposed toB. thuringiens is and NPV was<4% while mortality from 2,4-DB was<7%. The toxicity of chemical insecticides to parasitoids and predators at reduced dosages in increasing order of toxicity was malathion > carbaryl > toxaphene > methyl parathion.     

A comparative analysis of the antioxidant activity of Kalanchoe juices

A study of the biological, including the antioxidant, activity of various medicinal plants with the aim of searching for the most active sources of biologically active compounds among them is, at present, of interest. In the present work, a comparative analysis of the antioxidant activity of juices from 14 Kalanchoe species, measured by the ammetric, voltammetric, and chemiluminescence methods has been performed. Among the samples examined, two members of the Kalanchoe genus were shown to have the highest antioxidant activity: Kalanchoe scapigera and K. rhombopilosa. They may appear to be richer sources of biologically active compounds compared with the currently used Kalanchoe species.     

Comparison of some antioxidant properties of plant extracts from Origanum vulgare,Salvia officinalis,Eleutherococcus senticosus and Stevia rebaudiana

Phenolic compounds from plants are known for their antioxidant properties and have been proposed as therapeutic agents to counteract oxidative stress. However, under normal circumstances, the body only receives a very small amount of these substances in the diet. We have investigated the effect of extracts from known and frequently used plants as part of diet, food seasoning, medicinal tea, and sweetener at different concentrations on the ability to scavenge free radicals, to affect antioxidant enzymes, and finally in the survival of cancer cell lines. We found extract concentrations of about 100 μg.ml^?1 more indicative in the assessment of all parameters investigated. Ginseng possessed a very good ability to scavenge superoxide and hydroxyl radicals, while stevia also manifested significant effects against hydroxyl radicals. Both extracts also showed NO decomposition ability. The antioxidant defense system against the excessive production of radicals in mitochondria was sufficient. In contrast, the range of operating concentrations for sage and oregano mainly presented no significant effects against reactive oxygen and nitrogen species. Taken together with the significantly reduced activity of glutathione peroxidase, this led to the depletion of glutathione. The demonstrated modulation of redox state capability was sufficient to affect the viability of all tested cancer cell lines, but especially A-549, CEM and HeLa by oregano extract. Results support the promising role of the tested extracts as a source of compounds for further in vivo studies with the ability to powerfully interfere with or modify the redox state of cells according to the type of disease, which is expected to be associated with oxidative stress.     

Biological activity of humus acids isolated from spruce wood decomposed by fungi

Biological activity of humic acid, hymatomelanic acid, lignofulvic acid, and fulvic acids isolated from peat, from spruce wood decomposed by the fungusFomes marginatus (Fr.) Gillet, and from spruce wood decomposed by the fungusPoria cinerascens Bres. was tested on cress seedlings (Lepidium sativum L.). The results evaluated by the analysis of variance indicate that humus acids show a high degree of affinity in their biological activity which is a condition for the applicability of the decomposition of wood by fungi as a model of the humus formation. Humic and hymatomelanic acids, products of an advanced step of humification, have a predominantly stimulatory effect especially on the hypocotyl. Lignofulvic acids and fulvic acids exert a rather inhibitory effect with the root being more affected.     

Stomatal and pavement cell density linked to leaf internal CO2 concentration

Background and Aims

Stomatal density (SD) generally decreases with rising atmospheric CO₂ concentration, C_a. However, SD is also affected by light, air humidity and drought, all under systemic signalling from older leaves. This makes our understanding of how C_a controls SD incomplete. This study tested the hypotheses that SD is affected by the internal CO₂ concentration of the leaf, C_i, rather than C_a, and that cotyledons, as the first plant assimilation organs, lack the systemic signal.

Methods

Sunflower (Helianthus annuus), beech (Fagus sylvatica), arabidopsis (Arabidopsis thaliana) and garden cress (Lepidium sativum) were grown under contrasting environmental conditions that affected C_i while C_a was kept constant. The SD, pavement cell density (PCD) and stomatal index (SI) responses to C_i in cotyledons and the first leaves of garden cress were compared. ¹³C abundance (δ¹³C) in leaf dry matter was used to estimate the effective C_i during leaf development. The SD was estimated from leaf imprints.

Key Results

SD correlated negatively with C_i in leaves of all four species and under three different treatments (irradiance, abscisic acid and osmotic stress). PCD in arabidopsis and garden cress responded similarly, so that SI was largely unaffected. However, SD and PCD of cotyledons were insensitive to C_i, indicating an essential role for systemic signalling.

Conclusions

It is proposed that C_i or a C_i-linked factor plays an important role in modulating SD and PCD during epidermis development and leaf expansion. The absence of a C_i–SD relationship in the cotyledons of garden cress indicates the key role of lower-insertion CO₂ assimilation organs in signal perception and its long-distance transport.     

Changes in heat-shock protein synthesis and thermotolerance of Arabodopsis thaliana seedlings resulting from Hsp90 inhibition by geldanamycin

The influence of geldanamycin (GA), a specific inhibitor of heat-shock protein Hsp90, on the synthesis of Hsp70 and Hsp90 and thermotolerance of Arabidopsis thaliana seedlings has been studied. Incubation of seedlings with GA under normal conditions induced synthesis of these stress proteins. Treatment of seeds with the Hsp90 inhibitor resulted in elevated constitutive levels of Hsp70 and Hsp90 in seedlings, as well as increased induction of their synthesis under heat shock. The GA effect increased with its concentration. Hsp up-regulation promoted thermotolerance of seedlings. The findings suggest autoregulation of heatshock protein synthesis and regulation of plant tolerance by Hsp90.     

Two novel phytotoxic substances from Leucas aspera

Leucas aspera (Lamiaceae), an aromatic herbaceous plant, is well known for many medicinal properties and a number of bioactive compounds against animal cells have been isolated. However, phytotoxic substances from L. aspera have not yet been documented in the literature. Therefore, current research was conducted to explore the phytotoxic properties and substances in L. aspera. Aqueous methanol extracts of L. aspera inhibited the germination and growth of garden cress (Lepidum sativum) and barnyard grass (Echinochloa crus-galli), and the inhibitory activities were concentration dependent. These results suggest that the plant may have phytotoxic substances. The extracts were then purified by several chromatographic runs. The final purification was achieved by reversed-phase HPLC to give an equilibrium (or inseparable) 3:2 mixture of two labdane type diterpenes (compounds 1 and 2). These compounds were characterized as (rel 5S,6R,8R,9R,10S,13S,15S,16R)-6-acetoxy-9,13;15,16-diepoxy-15-hydroxy-16-methoxylabdane (1) and (rel 5S,6R,8R,9R,10S,13S,15R,16R)-6-acetoxy-9,13;15,16-diepoxy-15-hydroxy-16-methoxylabdane (2) by spectroscopic analyses. A mixture of the two compounds inhibits the germination and seedling growth of garden cress and barnyard grass at concentrations greater than 30 and 3 μM, respectively. The concentration required for 50% growth inhibition (I₅₀) of the test species ranges from 31 to 80 μM, which suggests that the mixture of these compounds, are responsible for the phytotoxic activity of L. aspera plant extract.     

Microbial and metabolic characterization of a denitrifying phosphorus-uptake/side stream phosphorus removal system for treating domestic sewage

In this study, an advanced wastewater treatment process, the denitrifying phosphorus/side stream phosphorus removal system (DPR-Phostrip), was developed for the purpose of enhancing denitrifying phosphorus removal. The enrichment of denitrifying phosphorus-accumulating organisms (DPAOs) and the microbial community structure of DPR-Phostrip were evaluated by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE), and the metabolic activity of seed sludge and activated sludge collected after 55 days of operation were evaluated by Biolog? analysis. This experimental study of DPR-Phostrip operation showed that nutrients were removed effectively, and denitrifying phosphorus removal was observed during the pre-anoxic period. PCR-DGGE analysis indicated that DPR-Phostrip supported DPAO growth while inhibiting PAOs and GAOs. The major dominant species in DPR-Phostrip were Bacteroidetes bacterium, Saprospiraceae bacterium, and Chloroflexi bacterium. Moreover, the functional diversity indices calculated on the basis of Biolog analysis indicated that DPR-Phostrip had almost no effect on microbial community diversity but was associated with a shift in the dominant species, which confirms the results of the PCR-DGGE analysis. The results for average well color development, calculated via Biolog analysis, showed that DPR-Phostrip had a little impact on the metabolic activity of sludge. Further principal component analysis suggested that the ability to utilize low-molecular-weight organic compounds was reduced in DPR-Phostrip.     

Cloning and analysis of DNA sequences from Streptomyces hygroscopicus encoding geldanamycin biosynthesis

A gene library constructed from large (20 kb) fragments of total DNA from the geldananmycin-producing strain Streptomyces hygroscopicus 3602 cloned in the plasmid vector pIJ61 were used to transform S. lividans TK24. Three transformants of about 800 tested were found to have acquired the ability to produce an antibiotic lethal to a geldanamycin-sensitive strain of Bacillus subtilis. The plasmids isolated from these transformants, pIA101, pIA102 and pIA103, each contained an insert of 15 kb. A 4.5 kb DNA fragment from the insert in pIA102 hybridised to DNA from S. hygroscopicus 3602 and to DNA encoding part of the erythromycin polyketide synthase but not to S. lividans TK24 DNA. The integration-defective phage vector C31 KC515 containing this 4.5 kb fragment was able to lysogenise S. hygroscopicus 3602 to produce lysogens defective in geldanamycin production. Loss of the prophage restored the ability to produce geldanamycin. Extracts of fermentation broth cultures of S. lividans containing pIA101, pIA102 and pIA102 and pIA103 analysed by thin-layer chromatography (TLC) contained compounds identical or very similar to purified geldanamycin, which were not present in S. lividans. These compounds showed a mass spectrum indistinguishable from geldanamycin. The evidence suggests that the clones contain DNA sequences encoding functions required for geldanamycin biosynthesis including components of the polyketide synthase.     

Cytotoxic activity and mechanism of action of metabolites from the Goniothalamus genus

The World Health Organization estimates that 4 billion people or 80 % of the population use plants for curative purposes or for their natural health benefits. Accordingly, biodiversity is an important source of active natural products especially used in traditional medicine as healers transmitted knowledge of traditional usage of medicinal plants from generation to generation whereas pharmacologically active compounds within remained obscure. The present review documents cytotoxicity and anti-cancer potential of known compounds of the Goniothalamus species from the Annonaceae family existing in tropical and subtropical Asia and being intensively used for medicinal purposes.