Phyllostoxin and phyllostin, bioactive metabolites produced by Phyllosticta cirsii, a potential mycoherbicide for Cirsium arvense biocontrol

Phyllosticta cirsii, a fungal pathogen isolated from diseased Cirsium arvense leaves and evaluated as a biocontrol agent of this noxious perennial weed, produces different phytotoxic metabolites with potential herbicidal activity when grown in liquid cultures. Phyllostictines A-D, four novel oxazatricycloalkenones, were recently isolated from this pathogen and chemically and biologically characterized. Further purification of the same organic extract provided two other metabolites, named phyllostoxin (1) and phyllostin (2), which were characterized by spectroscopic technique (essentially NMR and MS). Phyllostoxin and phyllostin proved to be a new pentasubstituted bicyclo-octatrienyl acetic acid ester and a new pentasubstituted hexahydrobenzodioxine carboxylic acid methyl ester, respectively. When tested on punctured C. arvense leaves, phyllostoxin proved to be highly phytotoxic, causing rapid and large necrosis, whereas phyllostin had no phytotoxicity in this bioassay. This is not surprising, considering the noteworthy structural differences between the two compounds, suggesting the presence of active functional groups in phyllostoxin not present in the other metabolite. These results further support the focused approach of finding novel metabolites with herbicidal properties by looking at the culture extracts of weed fungal pathogens.     

Synthesis and insect antifeedant activity of precocene derivatives with lactone moiety

Starting from precocenes I and II, four of their derivatives with a lactone moiety were obtained. The compounds have been assessed as antifeedants against several diverse insect species including the storage pests the confused flour beetle (Tribolium confusum Duv., larvae and adults), the granary weevil beetle (Sitophilus granarius L., adults), and the khapra beetle (Trogoderma granarium Ev., larvae) and against the herbivorous pest insects Colorado potato beetle (Leptinotarsa decemlineata Say, adults and larvae) and aphids (Myzus persicae Sulz.). Precocenes, especially precocene II, showed a very strong antifeedant effect against all storage pests and aphids. The introduction of a lactone moiety caused a decrease in antifeedant activity against these species. Both precocenes were moderately active against L. decemlineata adults. The best antifeedants to this species were precocene derivatives, especially iodolactones. The introduction of iodine into a molecule had a great effect on the antifeedant activity of those compounds.     

Soil amidase activity in polyacrylamide-treated soils and potential activity toward common amide-containing pesticides

 Polyacrylamide (PAM) is currently used as an irrigation water additive to significantly reduce the amount of soil erosion that occurs during furrow irrigation of crops. Elevated soil amidase activity specific toward the large PAM polymer has been reported in PAM-treated field soils; the substrate specificity of the induced amidase is uncertain. PAM-treated and untreated soils were assayed for their capacity to hydrolyze the amide bond in carbaryl (Sevin), diphenamid (Dymid), and naphthalene acetamide. Based on results obtained with a soil amidase assay, there was no difference between PAM-treated and untreated soils with respect to the rate of amide bond hydrolysis of any of the agrochemicals tested. It appears that under these assay conditions the PAM-induced soil amidase is not active toward the amide bonds within these molecules. However, carbaryl was hydrolyzed by a different soil amidase. To our knowledge, this is the first soil enzyme assay-based demonstration of the hydrolysis of carbaryl by a soil amidase. Received: 23 June 1999     

Insect antifeedant activity of flavones and chromones against Spodoptera litura

The antifeedant polymethylated flavones 5-hydroxy-3,6,7,8,4'-heptamethoxyflavone, 5-hydroxy-3,6,7,8-tetramethoxyflavone, and 5,6-dihydroxy-3,7-dimethoxyflavone have been isolated from the cudweed, Gnaphalium affine D. Don (Compositae). These flavonoids and authentic analogues showed insect antifeedant activity against the common cutworm (Spodoptera litura F.). In a previous paper, it was suggested that there was no substituent on the B-ring of the flavonoid for the beneficial antifeedant activity against the common cutworm. These flavonoids having a phenyl group as the B-ring and the chromone as elimination of the B-ring from the flavonoids were used to test the hypothesis of the previously described B-ring effect. The known fact is that Sculletaria baicarensis (Rutaceae) produced the 2-phenyl flavone. Test compounds and their methylated derivatives were prepared from this material for the structure-activity relationship (SAR) study of insect antifeedant activity. In spite of the 2-phenyl flavonoids, some tested compounds did not show any insect antifeedant activity against the common cutworm, although these inactive flavonoids were deficient in the 6-substituent group on the A-ring of the flavonoid. This 6-position-substituted derivative almost showed strong insect antifeedant activity against common cutworm. Moreover, the tested flavonoids having a hydroxyl group as a substituent on any of the positions tended to increase the activity. These results suggested the importance of the 6-position substitution on the flavonoid; however, hydrophilic substituents decreased the activity. Baicalein (5,6,7-trihydroxyflavone) derivatives did not show any activity despite having the 6-substituent derivative. Although the activity of some chromones increased the activity of the flavone, the bulky B-ring was a disadvantage for the antifeedant activity. It was suggested that the charge on C(3) and C(5) of the flavonoid was important for the biological activity. Additionally, an adequate hydrogen bonding property, which is different from lipophilicity, was an advantage for the activity on the basis of a QSAR analysis.     

Synthesis and insect antifeedant activity of aurones against Spodoptera litura larvae

A series of aurones were prepared from various phenols via phenoxy acetic acids and coumaranones and evaluated for insect antifeedant activity against the common cutworm (Spodoptera litura). The naturally occurring aurone was most active at an ED50 of 0.12 micromol/cm2. The synthetic precursor, coumaranones, showed that the introduction of methoxyl and methyl groups to the benzene ring increased insect antifeedant activity. Similarly, the tested aurones showed that the introduction of methoxyl group to the A and/or B rings increased the insect antifeedant activity, but 4,5,6- and 3',4',5'-trisubstituted compounds did not show this activity in this test. The hydroxylation of aurones in the B ring should be disadvantageous for insect antifeedant activity against S. litura. Although the melting points did not correlate well with the insect antifeedant activity, compounds that were nearly inactive had high melting points. A significant correlation was noted between biological activity (pED50) and a hydrogen-bonding parameter calculated from the Rf value obtained from SiOH thin-layer chromatography and a lipophilicity parameter (log k) calculated from the retention time in ODS high-performance liquid chromatography. The respective correlation coefficients (r) were -0.83 and -0.70. The introduction of alkoxy and alkyl groups along with adequate hydrogen bonding seems to contribute to the antifeedant activity of the compounds tested.     

Herbicidal potential of ophiobolins produced by Drechslera gigantea

Drechslera gigantea, a potential mycoherbicide of grass weeds, was isolated in Florida from naturally infected large crabgrass (Digitaria sanguinalis); it produces phytotoxic metabolites in liquid culture. The main metabolite was identified by spectroscopic methods and optical properties as ophiobolin A (1), a well-known phytotoxic sesterterpene produced by several phytopathogenic fungi of important crops and already extensively studied for its interesting biological activities. The other three minor metabolites proved to be related to ophiobolin A and were identified using the same techniques as 6-epi-ophiobolin A and 3-anhydro-6-epi-ophiobolin A (2 and 3) and ophiobolin I (4). Assayed on punctured detached leaves of several grass and dicotyledon weeds, ophiobolin A proved to be on average more phytotoxic as compared to the other related compounds. Some structural features appear to be important for the phytoxicity, such as the hydroxy group at C-3, the stereochemistry at C-6, and the aldehyde group at C-7. Furthermore, grass weeds usually proved to be more sensitive to the phytotoxins than dicotyledons, on which ophiobolin A caused the appearance of large necrosis even at the lowest concentration assayed. This is the first report about the production of ophiobolins from D. gigantea and of the proposed use as potential natural herbicides against grass weeds.     

Chemical basis for the antifeedant activity of natural hydroxamic acids and related compounds

Natural hydroxamic acids and related compounds derived from the 1,4-benzoxazin-3-one structure show antifeedant activity against the aphid Rhopalosiphum padi. This antifeeding activity is based on the electrophilic character of the hydroxamic acid function, the opening of the hemiacetal function and the lipophilic character of the molecule. In addition, the antifeedant activity of the aqueous extracts of different tissues of Acanthus mollis (Acanthaceae) was determined. The activity observed is attributed to the presence of 2,4-dihydroxy-1,4-benzoxazin-3-one in the extracts.     

Rumex induratus leaves: interesting dietary source of potential bioactive compounds

The phenolic compounds of Rumex induratus leaves were determined by HPLC-DAD-MS/MS-ESI. The results revealed a profile composed of 19 compounds: caffeoyl-hexoside, two p-coumaroyl-hexoside isomers, feruloyl-hexoside, sinapoyl-hexoside, 6-C-hexosyl-quercetin, 8-C-hexosyl-luteolin, 6-C-hexosyl-luteolin, 6-C-hexosyl-apigenin, 3-O-hexosyl-quercetin, 3-O-rutinosyl-quercetin, 7-O-hexosyl-diosmetin, 3-O-rutinosyl-isorhamnetin, 7-O-(acetyl)-pento-hexosyl-diosmetin, 6-C-hexosyl-genkwanin, and four unidentified O-glycosyl-C-glycosylflavones. The quantification of the identified phenolics by HPLC-DAD showed 6-C-hexosyl-luteolin as the main compound. Organic acid composition was determined by HPLC-UV, revealing a high content of oxalic acid. R. induratus was also investigated for its capacity to act as a scavenger of DPPH and superoxide radicals. Good antioxidative results were obtained against both radicals. Unlike other species of the genus Rumex, R. induratus did not present any anthraquinone derivative.     

The enhancement of bioactive potential in Vitis vinifera leaves by application of microspheres loaded with biological and chemical agents

An overview of a research on Vitis vinifera plants treated with a chemical (calcium and magnesium ions) and biological (Trichoderma viride) agents simultaneously loaded in alginate microspheres was presented. Microspheres were applied at two growth stages: before flowering and berries pea-size. Physicochemical characteristics of leaves after the two growth stages and grapes were measured in terms of bioactive components content and antioxidant activity. After the treatments, vine leaves reached a significant increase in almost all measured parameters (polyphenols, antioxidant capacity, β-carotene, and chlorophyll) compared to the control. The highest total chlorophyll content was found after the treatment with microspheres containing Mg²⁺/Ca²⁺ cations, and T. viride. The treatments enhanced Vitis vinifera leaves in terms of bioactive potential and can be further used as a functional food. As compared to the control, somewhat elevated values of total polyphenols and antioxidant activity were found on the grape samples.     

Purification and characterization of a rhamnose-binding chinook salmon roe lectin with antiproliferative activity toward tumor cells and nitric oxide-inducing activity toward murine macrophages

In this study, a rhamnose-binding lectin from the roe of chinook salmon (Oncorhynchus tshawytscha) was purified and characterized, and its biological activities were examined in several model systems. Chinook salmon roe lectin had a molecular mass of 30 kDa and agglutinated rabbit and bovine erythrocytes. The hemagglutination activity of the lectin was not affected by metal ions. The lectin was stable up to 70 °C and between pH 4 and pH 11. Chinook salmon roe lectin did not exert antifungal activity toward the fungal species tested and did not exhibit mitogenic response toward mouse splenocytes up to a concentration of 5 mg/mL. The lectin had selective antiproliferative activity toward human breast cancer MCF-7 cells and hepatoma Hep G2 cells. It also induced the production of nitric oxide from mouse peritoneal macrophages. This is the first report that demonstrates these biological activities from chinook salmon roe lectin.     

Urolithins, ellagic acid-derived metabolites produced by human colonic microflora, exhibit estrogenic and antiestrogenic activities

Urolithins A and B (hydroxy-6H-dibenzo[b,d]pyran-6-one derivatives) are colonic microflora metabolites recently proposed as biomarkers of human exposure to dietary ellagic acid derivatives. Molecular models suggest that urolithins could display estrogenic and/or antiestrogenic activity. To this purpose, both urolithins and other known phytoestrogens (genistein, daidzein, resveratrol, and enterolactone) were assayed to evaluate the capacity to induce cell proliferation on the estrogen-sensitive human breast cancer MCF-7 cells as well as the ability to bind to alpha- and beta-estrogen receptors. Both urolithins A and B showed estrogenic activity in a dose-dependent manner even at high concentrations (40 microM), without antiproliferative or toxic effects, whereas the other phytoestrogens inhibited cell proliferation at high concentrations. Overall, urolithins showed weaker estrogenic activity than the other phytoestrogens. However, both urolithins displayed slightly higher antiestrogenic activity (antagonized the growth promotion effect of 17-beta-estradiol in a dose-dependent manner) than the other phytoestrogens. The IC(50) values for the ERalpha and ERbeta binding assays were 0.4 and 0.75 microM for urolithin A; 20 and 11 microM for urolithin B; 3 and 0.02 for genistein; and 2.3 and 1 for daidzein, respectively; no binding was detected for resveratrol and enterolactone. Urolithins A and B entered into MCF-7 cells and were metabolized to yield mainly urolithin-sulfate derivatives. These results, together with previous studies regarding absorption and metabolism of dietary ellagitannins and ellagic acid in humans, suggest that the gut microflora metabolites urolithins are potential endocrine-disrupting molecules, which could resemble other described "enterophytoestrogens" (microflora-derived metabolites with estrogenic/antiestrogenic activity). Further research is warranted to evaluate the possible role of ellagitannins and ellagic acid as dietary "pro-phytoestrogens".     

Characterization of new bisphenol a metabolites produced by CD1 mice liver microsomes and S9 fractions

Bisphenol A [2,2-bis(4-hydroxyphenyl)propane] (BPA) is a widely used industrial chemical resulting in occupational and consumer exposure. BPA possesses weak estrogenomimetic activity and can be cytotoxic, though the underlying mechanisms of its toxicity toward cells are not completely understood. The metabolism of BPA by CD1 mice liver microsomal and S9 fractions was investigated. Nine metabolites were isolated and characterized using HPLC and mass spectrometry. Many of these metabolites were characterized for the first time in mammals, namely isopropyl-hydroxyphenol (produced by the cleavage of BPA), a bisphenol A glutathione conjugate, glutathionyl-phenol, glutathionyl 4-isopropylphenol, and BPA dimers. Most of these metabolites apparently share a common metabolic pathway, for which considerable evidence supports the hypothesis of the production of a reactive intermediate, and also helps explain BPA cytotoxicity.     

Antifungal activity of borrelidin produced by a Streptomyces strain isolated from soybean

In this study, an endophytic Streptomyces sp. neau-D50 with strong antifungal activity against Phytophthora sojae was isolated from healthy soybean root, using an in vitro screening technique. A bioactivity-guided approach was then employed to isolate and determine the chemical identity of bioactive constituents with antifungal activity from strain neau-D50. The structure of the antifungal metabolite was elucidated as borrelidin on the basis of spectral analysis. To our knowledge, this is the first report that borrelidin has strong antifungal activity against dominant race 1 of P. sojae with EC(50) and EC(95) of 0.0056 and 0.026 mg/L, respectively. The values were respectively 62.5- and 262.3-fold lower than those of the commercial fungicide metalaxyl, which has been used to treat soybean seed for the control of P. sojae . The in situ bioassays demonstrated that borrelidin at 10 mg/L reduced P. sojae race 1 lesions on soybean seedlings by 94.72% without affecting root growth. Thus, borrelidin might be a promising candidate for new antifungal agents against P. sojae.     

Effect of pH and temperature on comparative antioxidant activity of nonenzymatically browned proteins produced by reaction with oxidized lipids and carbohydrates

The antioxidative activity of nonenzymatically browned bovine serum albumin (BSA) produced by reaction with ribose (RI), hydroperoxides of methyl linoleate oxidation (HP), and secondary products of methyl linoleate oxidation (SP), at different pHs (4, 7, and 10) and temperatures (25, 37, 50, 80, and 120 degrees C), was studied to compare the antioxidative effects of carbohydrate- and oxidized lipids-modified proteins. The modified proteins (RIBSA, HPBSA, and SPBSA) were tested for antioxidative activity (at 100 ppm) in soybean oil using the thiobarbituric acid-reactive substances (TBARS) assay. All of them decreased significantly (p < 0.05) the TBARS formation in the oil and exhibited different effectiveness as a function of the temperature and the pH of the medium. In addition, there was a good correlation between the antioxidative activity of the protein and the amino acid losses produced during the nonenzymatic browning. These results are in agreement with an analogous and complimentary contribution of both Maillard and oxidized lipid/protein reactions to the antioxidative activity produced in foods during processing and storage.     

Antioxidant and anti-inflammatory potential of hesperetin metabolites obtained from hesperetin-administered rat serum: an ex vivo approach

In recent years much attention has been focused on the pharmaceutical relevance of bioflavonoids, especially hesperidin and its aglycon hesperetin in terms of their antioxidant and anti-inflammatory actions. However, the bioactivity of their metabolites, the real molecules in vivo hesperetin glucuronides/sulfates produced after ingestion, has been poorly understood. Thus, the study using an ex vivo approach is aimed to compare the antioxidant and anti-inflammatory activities of hesperidin/hesperetin or hesperetin metabolites derived from hesperetin-administered rat serum. We found that hesperetin metabolites (2.5-20 μM) showed higher antioxidant activity against various oxidative systems, including superoxide anion scavenging, reducing power, and metal chelating effects, than that of hesperidin or hesperetin. The data also showed that pretreatment of hesperetin metabolites (1-10 μM) within the range of physiological concentrations, compared to hesperetin, significantly inhibited nitric oxide (NO) and prostaglandin E(2) (PGE(2)) production, as evidenced by the inhibition of their precursors, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) protein levels without appreciable cytotoxicity on LPS-activated RAW264.7 macrophages or A7r5 smooth muscle cells. Concomitantly, hesperetin metabolites dose-dependently inhibited LPS-induced intracellular reactive oxygen species (ROS). Furthermore, hesperetin metabolites significantly downregulate LPS-induced nuclear factor-κB (NF-κB) activation followed by the suppression of inhibitor-κB (I-κB) degradation and phosphorylation of c-Jun N-terminal kinase1/2 (JNK1/2) and p38 MAPKs after challenge with LPS. Hesperetin metabolites ex vivo showed potent antioxidant and anti-inflammatory activity in comparison with hesperidin/hesperetin.     

Above- and below-ground interactions with agricultural management: Effects of soil microbial communities on barley and aphids

Recent research has shown that agricultural management affects microbial biomass and community composition. We investigated the functional implications of such effects in terms of barley biomass production and nutrient acquisition, and whether changes in barley nutrient status affected aphid fecundity. Soils were collected from conventional, ley and organic arable fields and used as inocula in a glasshouse experiment. We determined microbial biomass and community composition using PLFA. We investigated barley growth and nutrient responses to the different soil inoculums, and the impact of excluding arbuscular mycorrhizal fungi (AMF). Aphids were applied to plants within clip cages and numbers of offspring counted. Microbial biomass and community composition were unaffected by agricultural management. The microbial communities altered root and shoot biomass and nutrient allocation, but had no effect on grain yield. Exclusion of AMF significantly increased shoot biomass but reduced grain yield. Aphid fecundity was not significantly affected by the microbial community or shoot nitrogen. We conclude that agricultural intensification does not necessarily have negative consequences for above- and below-ground interactions, and microbial communities from conventionally managed soils may offer equal benefit to crop productivity and nutrition as those from organically managed soils.     

Hydrocarbon degradation potential and activity of endophytic bacteria associated with prairie plants

Phytoremediation systems for organic compounds such as petroleum hydrocarbons rely on a synergistic relationship between plants and their root-associated microbial communities. To determine the probable role of endophytic bacterial communities in these systems, this study examined both rhizosphere and endophytic communities of five different plant species at a long-term phytoremediation field site. Hydrocarbon degradation potential and activity were assessed using MPN assays, PCR analysis of catabolic genes associated with hydrocarbon degradation, and mineralization assays with C-14 labeled hydrocarbons. Microbial community structure in each niche was assessed by DGGE analysis of 16S rRNA gene fragments and subsequent band sequencing. Both endophytic degrader populations and endophytic degrader activity showed substantial inter-species variation, largely independent of that shown by the respective rhizosphere populations. Endophytic hydrocarbon degradation was linked to dominant bacterial endophytes. Pseudomonas spp. dominated endophytic communities exhibited increased alkane hydrocarbon degradation potential and activity, while Brevundimonas and Pseudomonas rhodesiae dominated endophytic communities were associated with increased PAH degradation potential and activity. In one plant species, Lolium perenne, increased endophytic alkane hydrocarbon degradation was associated with increased rhizosphere alkane degradation and decreased rhizosphere PAH degradation. Our results show that diverse plant species growing in weathered-hydrocarbon contaminated soil maintain distinct, heterogeneously distributed endophytic microbial populations, which may impact upon the ability of plants to promote the degradation of specific types of hydrocarbons.     

Lipid fractions with aggregatory and antiaggregatory activity toward platelets in fresh and fried cod (Gadus morhua): correlation with platelet-activating factor and atherogenesis

Cod (Gadus morhua) is a popular part of the diet in many countries on both sides of the North Atlantic; in most cases it is consumed fried. In this study, total lipids of cod muscle were separated into neutral and polar lipids, which were further fractionated by HPLC. The lipid fractions were tested in vitro, against washed rabbit platelets, for the probable existence of lipid compounds that either exhibit an action similar to that of platelet-activating factor (PAF) or inhibit the action of PAF. The platelet bioassay was used to evaluate total lipids, total polar lipids, and total neutral lipids, before any further separation. Detection of these compounds in fresh and fried cod could be used to evaluate the nutritional value of this important fish. The in vitro biological study of lipids showed that in fresh cod lipid fractions, ranges of PAF-like and anti-PAF-like activities were present, whereas in fried cod lipid fractions, both neutral and polar, anti-PAF activities were mainly observed. Because it has already been reported that PAF is involved in atheromatosis generation, the existence of PAF inhibitors in cod may contribute to the possible protective role of fish, in this case cod, against atherosclerosis.     

Mycotoxins and other secondary metabolites produced in vitro by Penicillium paneum Frisvad and Penicillium roqueforti Thom isolated from baled grass silage in Ireland

Secondary metabolites produced by Penicillium paneum and Penicillium roqueforti from baled grass silage were analyzed. A total of 157 isolates were investigated, comprising 78 P. paneum and 79 P. roqueforti isolates randomly selected from more than 900 colonies cultured from bales. The findings mostly agreed with the literature, although some metabolites were not consistently produced by either fungus. Roquefortine C, marcfortine A, and andrastin A were consistently produced, whereas PR toxin and patulin were not. Five silage samples were screened for fungal metabolites, with two visually moldy samples containing up to 20 mg/kg of roquefortine C, mycophenolic acid, and andrastin A along with minor quantities (0.1-5 mg/kg) of roquefortines A, B, and D, festuclavine, marcfortine A, and agroclavine. Three visually nonmoldy samples contained low amounts of mycophenolic acid and andrastin A. The ability of both molds to produce a diverse range of secondary metabolites in vitro and in silage should be a concern to livestock producers.     

Antioxidant activity and bioactive compounds of tea seed (Camellia oleifera Abel.) oil

The oil of tea seed (Camellia oleifera Abel.) is used extensively in China as cooking oil. The objectives of this study were to investigate the antioxidant activity of tea seed oil and its active compounds. Of the five solvent extracts, methanol extract of tea seed oil exhibited the highest yield and the strongest antioxidant activity as determined by DPPH scavenging activity and Trolox equivalent antioxidant capacity (TEAC). Two peaks separated from the methanol extract by HPLC contributed the most significant antioxidant activity. These two peaks were further identified as sesamin and a novel compound: 2,5-bis-benzo[1,3]dioxol-5-yl-tetrahydro-furo [3,4-d][1,3]dioxine (named compound B) by UV absorption and characterized by MS, IR, 1H NMR, and 13C NMR techniques. Sesamin and compound B decreased H2O2-mediated formation of reactive oxygen species in red blood cells (RBCs), inhibited RBCs hemolysis induced by AAPH, and increased the lag time of conjugated dienes formation in human low-density lipoprotein. The results indicate that both compounds isolated from tea seed oil exhibit remarkable antioxidant activity. Apart from the traditional pharmacological effects of Camellia oleifera, the oil of tea seed may also act as a prophylactic agent to prevent free radical related diseases.