Stagonolides J and K and Stagochromene A, Two New Natural Substituted Nonenolides and a New Disubstituted Chromene-4,5-dione Isolated from Stagonospora cirsii S-47 Proposed for the Biocontrol of Sonchus arvensis.

Two new natural 10-membered macrolides (1, 2) and one chromene-4,5-dione derivative (3), named stagonolides J and K and stagochromene A, respectively, were isolated from the phytopathogenic fungus Stagonospora cirsii S-47, together with two known compounds, stagonolide A (4) and herbarumin I (5). Stagonolides J and K and stagochromene A were characterized as (5E,7R*,8S*,9R*)-7,8-dihydroxy-9-propyl-5-nonen-9-olide, (5E,7R,9S)-7-hydroxy-9-propyl-5-nonen-9-olide, and (2R*,3R*)-3-hydroxy-2-propyltetrahydro-2H-chromene-4,5(3H,4aH)-dione, respectively, by spectroscopic (mostly by NMR and ESIMS) data. Compounds 1-5 showed different rates of phytotoxic activity on punctured leaf discs of Sonchus arvensis. The antimicrobial, cytotoxic, and antiprotozoal activity of isolated compounds was also evaluated. Based on our data, stagonolide K and herbarumin I can be proposed as a potential scaffold for the development of a new natural herbicide and estimated as possible selection/quality markers of a bioherbicide based on S. cirsii, while stagonolide A can be considered as a mycotoxin.

Colletochlorins E and F, New Phytotoxic Tetrasubstituted Pyran-2-one and Dihydrobenzofuran, Isolated from Colletotrichum higginsianum with Potential Herbicidal Activity.

A new tetrasubstituted pyran-2-one and a new dihydrobenzofuran, named colletochlorins E and F (1 and 2, respectively), were isolated from the culture filtrates of the fungus Colletotrichum higginsianum together with the already known colletochlorin A, 4-chloroorcinol, and colletopyrone. Colletochlorin E, the main metabolite, and colletochlorin F were characterized by spectroscopic (NMR, HRESIMS) and chemical methods as 3-[7-chloro-4-hydroxy-2-(1-hydroxy-1-methylethyl)-6-methyl-2,3-dihydrobenzofuran-5-ylmethyl]-4-hydroxy-5,6-dimethylpyran-2-one and 7-chloro-2-(1-hydroxy-1-methylethyl)-6-methyl-2,3-dihydrobenzofuran-4-ol, respectively. The absolute configuration 2'S of 1 was deduced by X-ray diffractometric analysis, whereas 2S of 2 was deduced by comparison of its NMR and CD data with those of 1. When assayed by leaf puncture on Sonchus arvensis and tomato leaves, 2 caused quite large necrosis (>1 cm), whereas 4-chloroorcinol proved to be the most active compound. These results were confirmed by those obtained in assays on Lemna minor and Phelipanche ramosa seed germination. Furthermore 1, colletochlorin A and colletopyrone were less or modestly active in the latter assay, respectively. Interestingly, the phytotoxicity was not associated with an antibiotic activity, whereas only 4-chloroorcinol and colletochlorin F exhibited zootoxic activity.

Behavior of native species Arrhenatherum elatius (Poaceae) and Sonchus transcaspicus (Asteraceae) exposed to a heavy metal-polluted field: plant metal concentration, phytotoxicity, and detoxification responses.

The application of vegetation cover for the phytomanagement of heavy metal-polluted soils needs prior investigation on the suitability of plant species. In this study, behaviors of Arrhenatherum elatius and Sonchus transcaspicus, two native perennial grasses that currently grow in a mine tailing, were investigated through plant metal concentration, phytotoxicity and their detoxification responses. Both of the species accumulated Ni, Cu, Cd, Co, Mn, Pb, Cr, and Zn in shoots far below criterion concentration as a hyperaccumulators; thus, neither of them were found to be hyperaccumulators. A. elatius accumulated metals in roots and then in shoots, on the contrary, in S. transcaspicus metals were preferentially accumulated in shoots. Plants exposure to such metals resulted in oxidative stress in the considered organs as indicated by the changes in chlorophyll fluorescence, chlorophyll contents, malondialdehyde (MDA) levels and antioxidative enzyme activities. A. elatius seemed to be more affected by metal-induced oxidative stress than S. transcaspicus. Correspondingly, S. transcaspicus showed a greater capacity to adapt to metal-induced oxidative stress, depending on more effective antioxidative defense mechanisms to protect itself from oxidative damage. These findings allowed us to conclude that both of these plant species could be suitable for the phytostabilization of metal-polluted soils.

[Basal bacteriosis of wheat and influence of agrotechnical methods on its spread].

Monitoring of bacterial diseases of wheat was conducted allowing for different doses of mineral fertilizers and crops predecessors. It is shown that symptoms of development of the basic disease of wheat, which is caused by Pseudomonas syringae pv. atrofaciens, varied depending on agrotechnical methods, stages of plant growth and environmental factors. Introduction of different doses of nitrogen, phosphate and potassium fertilizers, especially high ones, increases the damage of wheat by the agent of basal bacteriosis P. syringae pv. atrofaciens. Strains of this pathogen, isolated from the infected wheat plants, affect in the experiment such weeds as sow thistle, field horsetail, and couch grass.

Alternethanoxins A and B, polycyclic ethanones produced by Alternaria sonchi , potential mycoherbicides for Sonchus arvensis biocontrol.

Alternaria sonchi is a fungal pathogen isolated from Sonchus arvensis and proposed as a biocontrol agent of this noxious perennial weed. Different phytotoxic metabolites were isolated from solid culture of the fungus. Two new polycyclic ethanones, named alternethanoxins A and B, were characterized using essentially spectroscopic and chemical methods. Tested by leaf disk-puncture assay on the fungal host plant and a number of nonhost plants, alternethanoxins A and B were shown to be phytotoxic, whereas they did not possess antimicrobial activity tested at 100 microg/disk. Hence, alternethanoxins A and B have potential as nonselective natural herbicides. Some structure-activity relationship observations were also made.

Production of phytotoxins by Phoma exigua var. exigua, a potential mycoherbicide against perennial thistles.

The potential of the different Phoma exigua var. exigua strains for the biocontrol of the perennial weeds Sonchus arvensis and Cirsium arvense, occurring throughout temperate regions of the world, has been evaluated in previous studies. The majority of the above strains produced ascosonchine, a newly discovered enol tautomer of 4- pyridylpyruvic acid, whereas strains C-177 and S-9, though virulent to weeds, did not produce the above metabolite. In this study, it was demonstrated that the above two strains, grown in liquid and solid cultures, produced p-hydroxybenzaldehyde, cytochalasins B, F, Z2 and Z3, and deoxaphomin. When assayed on the leaves of both C. arvense and S. arvensis, p-hydroxybenzaldehyde was inactive, whereas deoxaphomin demonstrated the highest level of toxicity on leaves of S. arvensis. Cytochalasin Z2 appeared to be the less toxic cytochalasan on both plants according to the lack of the secondary hydroxyl group on C-7. Production of cytochalasins by P. exigua var. exigua strains isolated from C. arvense and S. arvensis is discussed in relation to chemotaxonomy and the biocontrol potential of the fungus.

Nonenolides and cytochalasins with phytotoxic activity against Cirsium arvense and Sonchus arvensis: a structure-activity relationships study.

A structure-activity relationships study was conducted assaying 15 natural analogues and derivatives belonging to two groups of organic compounds, nonenolides and cytochalasins, for their toxicity against the composite perennial weeds Cirsium arvense and Sonchus arvensis occurring through the temperate region of world. The toxic nonenolides (stagonolide, putaminoxin, pinolidoxin) and cytochalasins (deoxaphomin, cytochalasins A, B, F, T, Z2 and Z3) were isolated from phytopathogenic Stagonospora, Phoma and Ascochyta spp. The pinolidoxin (7,8-O,O'-diacetyl- and 7,8-O,O'-isopropylidene-pinolidoxin) and cytochalasins B (21,22-dihydro-, 7-O-acetyl- and 7,20-O,O'-diacetyl-cytochalasin B) derivatives were obtained by chemical modifications of the corresponding toxins. Among the 15 compounds tested, stagonolide and deoxaphomin proved to be the most phytotoxic to C. arvense and S. arvensis leaves, respectively. The tested phytotoxic nonenolides were stronger inhibitors of photosynthesis in C. arvense leaves than cytochalasines A and B. Stagonolide had less effect on membrane permeability in C. arvense leaves than cytochalasin B. Significant changes of light absorption by C. arvense leaves in visible and infrared spectra were caused by stagonolide. The functional groups and the conformational freedom of the ring, appear to be important structural features for the nonenolides toxicity, whereas and the presence of the hydroxy group at C-7, the functional group at C-20 and the conformational freedom of the macrocyclic ring are important for the cytochalasins toxicity.

The response of some common Egyptian plants to ozone and their use as biomonitors.

Relative sensitivity of five common Egyptian plant species namely, Senecio vulgaris, Malva parviflora, Sonchus oleraceus, Medicago sativa and Melilotus indicus to elevated levels of ozone has been studied. The plants were exposed to charcoal filtered air (CFA) and different levels of O3 (50 and 100 ppb) for 5 h per day. The studied parameters were recorded for five consecutive days after fumigation. The foliar injury varied significantly among species in a dose-dependent manner. Severe injury symptoms were recorded on the leaves of M. sativa. With the exception of M. parviflora, all species exhibited significant increases in the percentage reduction of the above-ground dry weight as a result of reductions in both leaf and stem dry weights. M. sativa showed a marked reduction in its relative growth rate at elevated levels of O3. The extent of chlorophyll a destruction was higher in both M. sativa and S. oleraceus than in the other species tested. No differences in the sensitivity of chlorophylls a+b and carotenoids to ozone levels were recorded in this work. Percentage reduction of ascorbic acid was higher in M. sativa and S. oleraceus, compared with the other species studied. With respect to relative percentages of proline, there was a significant difference in the responses of plants to ozone. According to the ozone resistance (R%), measured as relative growth rate, the test species were arranged in the descending order: M. parviflora>M. Indicus>S. Vulgaris>S. Oleraceus>M. sativa. In M. sativa, both determinant and correlation coefficients are well reflected in the relationship between its physiological response, its performance and ozone levels, supporting its recommendation as a candidate for biomonitoring in Egypt.