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In order to identify qualitative markers of a potential mycoherbicide against Canada thistle based on the mycelium of the fungus Stagonospora cirsii VIZR 1.41, changes in its pathogenicity and lipid profiles during submerged cultivation on liquid sucrose-soybean medium were analyzed. The fatty-acid composition of major lipids and the identification of molecular species of structural lipids were determined. The lipid composition during fungal growth changed together with its pathogenicity. The highly pathogenic mycelium of the fungus (at the log phase of growth) was characterized with the relatively highest content of structural lipids: phosphatidylcholine (PC), phosphatidylethanolamine (PE), and ergosterol (ES). Their relative concentration decreased with culture age and a decrease in pathogenicity. The highest lipid yield was found at the beginning of stationary growth phase (at the maximal biomass yield) of S. cirsii; triacylglycerides (TAGs) were the most abundant. The double-bond index of fatty acids in glycerolipids decreased with culture age, and the substitution of molecular PC species (34:2 versus 36:4) and PE (36:4 versus 34:2) was observed as well. High levels of ES, TAG, PC (in particular, 34:2 forms) and PE (36:4 forms) were presumed to be qualitative markers of S. cirsii mycelium.

Secondary metabolites were isolated from cultures of four geographically distant isolates of the cosmopolitan fungus, Bipolaris sorokiniana for intense biological characterization. Analysis of extracts from their liquid and solid cultures with TLC and HPLC-MS showed high similarity of their composition despite on fungal origin. From the extracts of B. sorokiniana 14 metabolites (terpenes, quinones, xanthones etc.) were isolated using column chromatography and preparative HPLC; among them, 12 known substances were identified. Chloromonilinic acid B (CAB) showed the highest level phytotoxic activity on wheat leaves. The most of isolated compounds inhibited growth of Bacillus subtilis, of which methyl-8,3-hydroxy-3-methyl-4-chloroxanthon-1-carboxilate (MMC) demonstrated the strongest activity. Some metabolites of B. sorokiniana (CAB and MMC) were shown to have insecticidal activity against common cereal aphid. All the compounds were cytotoxic (especially, cochlioqionones and fusaroproliferin) when tested on Sf9 cell line. However, no one was acute toxic for infusoria. Evidently, the production of multiple bioactive compounds makes B. sorokiniana a strong competitor in different ecological niches and a dangerous contaminant of grain.

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.

The effect of the nitrogen source (sodium nitrate and soybean meal) on the growth, pathogenicity, and lipid composition of mycelium of Stagonospora cirsii Davis VIZR 1.41, a potential mycoherbicide against Canada thistle (Cirsium arvens (L.) Scop.), was studied. The fungus grew significantly (two times) faster on sucrose-soybean meal medium (SSM) than on modified Czapek medium (CM). The fungal mycelium during the exponential growth phase demonstrated the maximal pathogenicity level on the third day on SSM and on the sixth day on CM. Canada thistle leaf tissues were more susceptible (25% higher development of necrotic lesion) to mycelium obtained on SSM than to mycelium obtained on CM. The nitrogen source strongly affected the lipid composition of S. cirsii mycelium. In S. cirsii mycelium obtained on SSM, the total lipid content was 1.7 times lower; the ratio of nonpolar lipids to polar lipids was three times lower than that for fungal mycelium grown on CM. Considerable differences were found in the composition of nonpolar (sterols and fatty acid) and polar (sphingolipids) lipids with respect to the nitrogen source in the culture medium. The higher contents of sterols, free fatty acids, and some glycoceramides in the mycelium of S. cirsii obtained on SSM may be related to its higher pathogenicity level and can serve as a marker of mycoherbicide quality.

Ten-membered lactones (nonenolides) demonstrate phytotoxic, antimicrobial, and fungicidal activity promising for the development of natural product-derived pesticides. The fungus Stagonospora cirsii is able to produce phytotoxic stagonolides A (1), J (2), K (3) and herbarumin I (4) with high yield. The aim of this study was to create a set of structurally related nonenolides and to reveal the structural features that affect their biological activity. Stagonolide A (1) and C-7 oxidized stagonolide K (11) showed the highest phytotoxicity in leaf puncture assay and agar seedlings assay. The oxidation of C-7 hydroxyl group (as in 1, acetylstagonolide A (10) and (11) led to the manifestation of toxicity to microalgae, Bacillus subtilis and Sf9 cells regardless of the configuration of C-9 propyl chains (R in 1 and 10, S in 11). C-7 non-oxidized nonenolides displayed none or little non-target activity. Notably, 7S compounds were more phytotoxic than their 7R analogues. Due to the high inhibitory activity against seedling growth and the lack of side toxicity, mono- and bis(acetyl)- derivatives of herbarumin I were shown to be potent for the development of pre-emergent herbicides. The identified structural features can be used for the rational design of new herbicides.

The study of fungal antibiotics in their competitive interactions with arthropods may lead to the development of novel biorational insecticides. Extracts of Alternaria tenuissima MFP253011 obtained using various methods showed a wide range of biological activities, including entomotoxic properties. Analysis of their composition and bioactivity allowed us to reveal several known mycotoxins and unidentified compounds that may be involved in the entomotoxic activity of the extracts. Among them, tenuazonic acid (TeA), which was the major component of the A. tenuissima extracts, was found the most likely to have larvicidal activity against Galleria mellonella. In the intrahaemocoel injection bioassay, TeA was toxic to G. mellonella and of Zophobas morio with an LT50 of 6 and 2 days, respectively, at the level of 50 µg/larva. Administered orally, TeA inhibited the growth of G. mellonella larvae and caused mortality of Acheta domesticus adults (LT50 7 days) at a concentration of 250 µg/g of feed. TeA showed weak contact intestinal activity against the two phytophages, Tetranychus urticae and Schizaphis graminum, causing 15% and 27% mortality at a concentration of 1 mg/mL, respectively. TeA was cytotoxic to the Sf9 cell line (IC50 25 µg/mL). Thus, model insects such as G. mellonella could be used for further toxicological characterization of TeA.

Antimicrobial, phytotoxic, and insecticidal activity of 20 isolates of 16 Alternaria species isolated from above-ground organs of weeds and wild herbaceous plants was determined. Assessment of the antibacterial activity by the agar blocks and paper disks methods revealed antibacterial activity against Bacillus subtilis and/or Pseudomonassyringae in over 70% of the isolates. Antifungal activity against Candida tropicalis was found in 30% of the isolates. The reporter system used in the work revealed no effect of the studied extracts on the ribosomes, although some of them inhibited topoisomerase. Extracts from the culture liquid of all Alternaria spp. isolates were toxic to isolated leaves of Arabidopsis thaliana and Elytrigia repens. Insecticidal activity of the extracts against vetch aphid (Megoura viciae) larvae was revealed in 40% of the isolates. Thus, fungi from the phyllosphere of weeds and wild herbaceous plants may exhibit a broad range of biological activity. This feature may probably be of practical importance for toxicological assessment of those weed pathogens that are evaluated as potential bioherbicides. Our results show that Alternaria fungi may play a significant regulatory role in formation of the communities of phyllosphere organisms and are promising producers of antimicrobial compounds with potentially new mechanisms of action.

Soil, enodphytic, and insect-pathogenic micromycetes of the genus Beauveria are widespread in nature and are important producers on mycoinsecticides, enzymes, and pharmacologically usable and toxic compounds. The goal of the work was to determine chemodiagnostic approaches to differentiation of Beauveria cryptic species using the strains B. bassiana BBL and B. pseudobassiana BCu22 by comparing their toxicological properties (insecticidal, antimicrobial, phytotoxic, cytotoxic, and esterase-inhibition activity) and metabolite profiles (TLC and HPLC/DAD patterns) of the extracts from the cultures of these fungi growing on different loose substrates, on solid and liquid media. It was shown that when the strains were cultured in liquid media (SDAY and Adamek medium) and on solid substrates (millet and Czapek agar medium), they could be differentiated by the extract yield and chromatographic profiles, as well as by their insecticidal, antifungal, and cytotoxic activity. Thus, antifungal properties were more pronounced in B. pseudobassiana BCu22 grown in liquid Adamek and SDAY media, while cytotoxic properties were more notable in B. bassiana BBL grown in Adamek medium and on millet. Insecticidal properties of the extracts from these cultures varied depending on the substrate composition. Since the extracts of the studied fungi exhibited a broad spectrum of biological activity, the toxic properties of Beauveria spp. should be considered in the course of assessment of safety of these fungi as bioinsecticides.

The fungus, Alternaria sonchi is considered to be a potential agent for the biocontrol of perennial sowthistle (Sonchus arvensis). A new chlorinated xanthone, methyl 8-hydroxy-3-methyl-4-chloro-9-oxo-9H-xanthene-1-carboxylate (1) and a new benzophenone derivative, 5-chloromoniliphenone (2), were isolated together with eleven structurally related compounds (3–13) from the solid culture of the fungus, which is used for the production of bioherbicidal inoculum of A. sonchi. Their structures were determined by spectroscopic (mostly by NMR and MS) methods. Alternethanoxins A and B, which were reported in A. sonchi earlier, were re-identified as moniliphenone and pinselin, respectively. The isolated compounds were tested for phytotoxic, antimicrobial, insecticidal, cytotoxic and esterase-inhibition activities. They did not demonstrate high phytotoxicity (lesions up to 2.5 mm in diameter/length at a concentration of 2 mg/mL) when tested on leaf disks/segments of perennial sowthistle (Sonchus arvensis) and couch grass (Elytrigia repens). They did not possess acute toxicity to Paramecium caudatum, and showed moderate to low cytotoxicity (IC50 > 25 µg/mL) for U937 and K562 tumor cell lines. However, chloromonilicin and methyl 3,8-dihydroxy-6-methyl-4-chloro-9-oxo-9H-xanthene-1-carboxylate (4) were shown to have antimicrobial properties with MIC 0.5–5 µg/disc. Compound 4 and chloromonilinic acid B were found to have contact insecticidal activity to wheat aphid (Schizaphis graminum) at 1 mg/mL. Compounds 2 and methyl 3,8-dihydroxy-6-methyl-9-oxo-9H-xanthene-1-carboxylate displayed selective carboxylesterase inhibition activity at concentration of 100 µg/mL. Therefore, the waste solid substrate for production of A. sonchi spores can be re-utilized for the isolation of a number of valuable natural products.

Two new natural 10-membered macrolides (

Chloromonilicin was isolated for the first time from Alternaria sonchi, a mycoherbicide proposed for the control of the noxious weed Sonchus arvensis. The already known alternethanoxins A and B and the three recently isolated phytotoxic polycyclic ethanones named alternethanoxins C-E were also isolated from the same source. Chloromonilicin was identified by spectroscopic data (essentially one-dimensional NMR, 2-dimensional NMR and high-resolution ESI-MS) and its structure was confirmed by single X-ray analysis, which also allowed the assignment of the absolute configuration. This latter was independently confirmed by electronic CD calculations. When chloromonilicin was tested for its antimicrobial activity, it was active at concentrations 0.5-1 μg per disc against four bacterial species and a yeast fungus. The compound inhibited conidial germination of four plant pathogens at concentration of 1-10 μg ml(-1). No phytotoxic activity of this antibiotic by leaf-disc puncture bioassay was detected.

Three new polycyclic ethanones, named alternethanoxins C-E, were isolated together with the well-known and closely related alternethanoxins A and B, from the solid culture of Alternaria sonchi, a fungal pathogen proposed for perennial sowthistle (Sonchus arvensis L.) biocontrol. Alternethanoxins C-E were characterized by spectroscopic methods (essentially NMR and HRESI MS) as 2'-dihydroxymethyl-2,5,6,6'-tetrahydroxy-3'-methoxy-biphenyl-3-carboxylic acid methyl ester, 1,4,6,9,10-pentahydroxy-7-methoxy-6H-benzo[c]chromene-2-carboxylic acid methyl ester, and 7,9-dihydroxy-2-methoxy-9H-4,8-dioxa-cyclopenta[def]phenanthrene-5-carboxylic acid methyl ester. When assayed on leaf segments of weeds (Sonchus arvensis and Elytrigia repens), alternethanoxins A and C showed phytotoxic activity inducing notable necrotic lesions. Alternethanoxins C and D possess notable antimicrobial activity when tested against Bacillus subtilis (MIC 10 μg/disc) and Candida tropicalis (MIC 25 μg/disc). Alternethanoxins A and B had low activity against these microbes, while alternethanoxin E was inactive.

New derivatives of phaeosphaeride A (PPA) were synthesized and characterized. Anti-tumor activity studies were carried out on the HCT-116, PC3, MCF-7, A549, К562, NCI-Н929, Jurkat, THP-1, RPMI8228 tumor cell lines, and on the HEF cell line. All of the compounds synthesized were found to have better efficacy than PPA towards the tumor cell lines mentioned. Compound 6 was potent against six cancer cell lines, HCT-116, PC-3, K562, NCI-H929, Jurkat, and RPMI8226, showing a 47, 13.5, 16, 4, 1.5, and 7-fold increase in anticancer activity comparative to those of etoposide, respectively. Compound 1 possessed selectivity toward the NCI-H929 cell line (IC50 = 1.35 &plusmn, 0.69 &mu, M), while product 7 was selective against three cancer cell lines, HCT-116, MCF-7, and NCI-H929, each having IC50 values of 1.65 &mu, M, 1.80 &mu, M and 2.00 &mu, M, respectively.

Derivatives of phaeosphaeride A (PPA) were synthesised and characterised; then anti-cancer studies were carried out on the A549 cancer cell line. It was found that the acetyl derivative (compound 3) displayed comparable in vitro cytotoxicity to that of PPA (EC50=49±7 μM and EC50=46±5 μM, respectively), while chloroacetyl derivative 6 (EC50=33±7 μM) was found to have better efficacy towards the A549 cancer cell line.

The herein synthesized 7-(4-methylphenyl)thiomethyl and 7-morpholylmethyl derivatives of natural phaeosphaeride A have lower cytotoxic activity towards the human lung adenocarcinoma A549 cell line compared to phaeosphaeride A. The presence of exocyclic C=C bond and N–OMe group in such compounds is suggested to be a factor in their antitumor activity.

Ambrosia artemisiifolia L. is responsible for serious allergies induced on humans. Different approaches for its control were proposed during the COST Action FA1203 “Sustainable management of Ambrosia artemisiifolia in Europe” (SMARTER). Fungal secondary metabolites often show potential herbicidal activity. Three phytotoxins were purified from the fungal culture filtrates of Colletotrichum gloeosporioides, isolated from infected leaves of A. artemisiifolia. They were identified by spectroscopic and chemical methods as colletochlorin A, orcinol and tyrosol (1, 2 and 3). The absolute configuration 6’R to colletochlorin A was assigned for the first time applying the advanced Mosher’s method. When assayed by leaf-puncture on A. artemisiifolia only 1 caused the appearance of large necrosis. The same symptoms were also induced by 1 on ambrosia plantlets associated with plant wilting. On Lemna minor, colletochlorin A caused a clear fronds browning, with a total reduction in chlorophyll content.

Giant hogweed is one of the most widespread invasive alien species of the Baltic region. The pycnidial fungus,Calophoma complanatais being evaluated as a potential bioherbicide for control ofHeracleum sosnowskyi. The aim of this work is to evaluate an ability of the potential mycoherbicideC.complanataMF-32.121 to overwinter in the conditions of Saint Petersburg area. Plants inoculated byC. complanataMF-32.121 successfully survives wintering in the conditions of Saint Petersburg area. Pearl barley covered byC. complanataMF-32.121 mycelium successfully survives wintering in the same conditions as well. When favorable conditions have arisen, theC. complanataMF-32.121 mycelium is capable to infecting young giant hogweed. Moreover, it was revealed that a change in the biochemical composition, namely, an increase in the level of trehalose, contributes to the manifestation of a greater tolerance ofC. complanataMF-32.121 mycelium to temperature-humidity conditions.

The Stagonospora cirsii mycelium is considered as the infectious basis of a potential mycoherbicide for the control of Canadian thistle and perennial sow thistle. Successful commercialization of mycoherbicides is often constrained by poor drying survival. In this study was shown that the highest viability of mycelium S. cirsii during drying is achieved in the stationary phase of growth. The mycelium in the stationary phase is characterized by maximum level of carbohydrates. We suggest the level of arabitol as a criterion evaluation of the mycelium resistance to drying. Culturing conditions, and especially the fermentation time, allow prediction of polyols and trehalose levels, which are very critical in enhancing the storage life and efficacy of biological control agent.

Antimicrobial, phytotoxic, and insecticidal activity of 30 fungal isolates obtained from leaves of weeds and wild herbaceous plants was assessed. Antibacterial, antifungal, phytotoxic, and insecticidal activity was found in over 50%, 40, 47, and 40% of the isolates, respectively. These findings may be important for tox� icological assessment of potential mycoherbicides, and may also provide a basis for investigation of the pat� terns of development of phyllosphere communities affected by fungal metabolites.

Phoma exigua var. exigua, a fungal pathogen isolated from Cirsium arvense and Sonchus arvensis, proposed as a biocontrol agent of this noxious perennial weeds, produces in liquid and solid cultures different phytotoxic metabolites with potential herbicidal activity. The phytotoxic cytochalasins B, F, Z2, and Z3 and deoxaphomin were previously identified together with p-hydroxybenzaldehyde. Using spectroscopic methods, four new cytochalasins, termed phomachalasins A–D, were isolated and characterized as three new closely related 26-oxa[16] and one new [15]cytochalasans. They belong to a new subgroup of cytochalasans bearing a 1,2,3,4,6,7-hexasubstituted bicycle[3.2.0]heptene joined to the macrocyclic ring. None of the four new metabolites showed phytotoxic or antimicrobial activity. The lack of both phytotoxic and antimicrobial activities showed by all phomachalasins A–D was probably due to the strong modification of both functionalities and conformational freedom of the macrocyclic ring caused by its junction with the bulky and quite rigid new bicycle, namely bicycle[3.2.0]heptene.

The article presents results of a study of weeds mycobiota in the Krasnodar Territory and Republic of Adygeya (North Caucasus) in 2002, 2004 and 2008. Micromycetes were found on 60 plant species of 48 genera and 20 families. We have identified 77 fungal species. The revealed species belong to 41 genera, 8 families and 7 orders of Oomycota, Ascomycota, Basidiomycota and anamorphic fungi.

The article presents results of studying the mycobiota of weeds and wild herbaceous plants in Primorie and Khabarovsk Territories in 2006. Micromycetes were found on 52 plant species of 46 genera and 21 families. Identified were 75 fungal species of 37 genera, 7 families and 6 orders of Oomycota, Ascomycota, Basidiomycota and anamorphic fungi.

Three new polycyclic ethanones, named alternethanoxins C-E, were isolated together with the well-known and closely related alternethanoxins A and B, from the solid culture of Alternaria sonchi, a fungal pathogen proposed for perennial sowthistle (Sonchus arvensis L.) biocontrol. Alternethanoxins C-E were characterized by spectroscopic methods (essentially NMR and HRESI MS) as 2'-dihydroxymethyl-2,5,6,6'-tetrahydroxy-3'-methoxy-biphenyl-3-carboxylic acid methyl ester, 1,4,6,9,10-pentahydroxy-7-methoxy-6H-benzo[c]chromene-2-carboxylic acid methyl ester, and 7,9-dihydroxy-2-methoxy-9H-4,8-dioxa-cyclopenta[def]phenanthrene-5-carboxylic acid methyl ester. When assayed on leaf segments of weeds (Sonchus arvensis and Elytrigia repens), alternethanoxins A and C showed phytotoxic activity inducing notable necrotic lesions. Alternethanoxins C and D possess notable antimicrobial activity when tested against Bacillus subtilis (MIC 10 μg/disc) and Candida tropicalis (MIC 25 μg/disc). Alternethanoxins A and B had low activity against these microbes, while alternethanoxin E was inactive.

A new 19-oxa-tricyclohenicosatetraenone and a new dioxacyclopropacycloundecene-10-carboaldehyde and its 6,7-dihydro derivative, named saponaroxins A–C, were isolated from the culture filtrate of Alternaria saponariae a fungal pathogen of the well-known medicinal plant Saponaria officinalis. Saponaroxins A–C were characterized by spectroscopic methods. When assayed on punctured leaf segments of two weeds, Sonchus arvensis and Elytrigia repens saponaroxins B–C were found to be phytotoxic. They demonstrated moderate antimicrobial activity and low toxicity against Paramecium caudatum. Saponaroxin A was acutely toxic to P. caudatum while showed no phytotoxic nor antimicrobial activity.

The asymmetric unit of the title compound, C15H23NO5, contains two independent molecules. Phaeosphaeride A contains two primary sections, an alkyl chain consisting of five C atoms and a cyclic system consisting of fused five- and six-membered rings with attached substituents. In the crystal, the molecules form layered structures. Nearly planar sheets, parallel to the (001) plane, form bilayers of two-dimensional hydrogen-bonded networks with the hydroxy groups located on the interior of the bilayer sheets. The network is constructed primarily of four O—H...O hydrogen bonds, which form a zigzag pattern in the (001) plane. The butyl chains interdigitate with the butyl chains on adjacent sheets. The crystal was twinned by a twofold rotation about thecaxis, with refined major–minor occupancy fractions of 0.718 (6):0.282 (6).

Three tetrasubstituted furopyrans, named chenopodolans A-C, were isolated together with the well known fungal metabolite (-)-(R)-6-hydroxymellein from the liquid culture of Phoma chenopodiicola, a fungal pathogen proposed for the biological control of Chenopodium album, a common worldwide weed of arable crops. The structures of chenopodolans A-C were established by spectroscopic and chemical methods as 2-(3-methoxy-2,6-dimethyl-7aH-furo[2,3-b]pyran-4-yl)- butane-2,3-diol, 1-(3-methoxy-2,6-dimethyl-7aH-furo[2,3-b]pyran-4-yl)ethanol and 3-methoxy-2,6-dimethyl-4-(1-methylpropenyl)-7aH-furo[2,3-b]pyran, respectively. The absolute configuration R to the hydroxylated secondary carbon (C-11) of the side chain at C-4 of chenopodolan A was determined by applying an advanced Mosher's method. Assayed by leaf puncture on host and non-host weeds chenopodolans A and B, and the 11-O-acetylchenopodolan A showed a strong phytotoxicity. These results showed that the nature of the side chain attached to C-4 is an important feature for the phytotoxicity. A weak zootoxic activity was only showed by chenopodolan B.©; 2013 Elsevier Ltd. All rights reserved.

Alternethanoxins A (1) and B (2) are fungal phytotoxins that are produced by Alternaria sonchi and have been recently characterized as new polycyclic ethanones. Triacetyl (3) and dimethyl (4) derivatives of compound 1 were evaluated together with alternethanoxins for their in vitro growth inhibitory activities in five human and one mouse cancer cell lines in comparison to the reference compound temozolomide (TMZ). Compounds 1-4 and TMZ displayed similar growth inhibitory activities, and these anticancer activities were equivalent in cancer cell lines that display certain levels of resistance to pro-apoptotic stimuli and those that are sensitive to pro-apoptotic stimuli. Of the six cancer cell lines under study, the human esophageal cancer cell line OE21 was the most sensitive to the four polycyclic ethanones. Computer-assisted phase-contrast microscopy (quantitative videomicroscopy) revealed that compounds 1, 2 and 4 displayed cytostatic rather than cytotoxic growth inhibitory effects, while compound 3 appeared to have cytotoxic effects. Thus, this study creates a stimulus for further structure-activity investigations with respect to the anticancer activities of compounds belonging to the alternethanoxin group. The observed toxicity does not seem to be affected by the stereochemistry of C-6 of the B ring, the presence of a hydroxy group at C-1 or the presence of a furan ring joining rings A and C in alternethanoxin B. The anticancer activity (cytostatic versus cytotoxic) of this type of compound could be affected by the chemical moieties present at the hydroxy groups at C-4 and C-6, as was observed for the cytostatic and cytotoxic activities of derivatives 4 and 3, respectively.

A strain of Ascochyta agropyrina var. nana was isolated from Elytrigia repens (quack grass), a noxious perennial weed widespread through the cold regions of the northen and southern hemispheres. Papyracillic acid was isolated for the first time from the fungal solid culture and identified using spectroscopic methods, including X-ray diffractometric and CD analysis for the assignment of the relative and absolute stereochemistries. Some key derivatives were prepared and used in a structure-activity relationship study. Tested by leaf disk-puncture assay, papyracillic acid at the concentration of 1 mg/mL was shown to be phytotoxic both for the host plant and a number of nonhost plants of the fungus. Papyracillic acid was active against bacteria (Xanthomonas campestris and Bacillus subtilis) and the fungus Candida tropicalis at 6 microg/disk. Derivatives of papyracillic acid were significantly less active than original toxin. However, the monoacetyl derivative of the toxin did not possess antimicrobial activity but remained highly phytotoxic to quack grass. Hence, papyracillic acid and its analogues have potential as nonselective herbicides of natural origin. Some structure-activity relationship observations for papyracillic acid and its derivatives were also made.

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.

Stagonospora cirsii Davis, a fungal pathogen isolated from Cirsium arvense (commonly called Canada thistle) and proposed as a potential mycoherbicide of this perennial noxious weed, produces phytotoxic metabolites in liquid and solid cultures. Stagonolide, the main phytotoxic metabolite, and five new related nonenolides, named stagonolides B−F, were isolated from the fungus. When grown on solid culture, nonenolide yields increased. A further four nonenolides were isolated and characterized by spectroscopy. Three were new compounds and named stagonolides G−I, and the fourth was identified as modiolide A, previously isolated from Paraphaeosphaeria sp., a fungus separated from the horse mussel. Leaf disk-puncture assays at 1 mg/mL of stagonolides H−I and modiolide A were phytotoxic to C. arvense. Only stagonolide H inhibited chicory seedling root growth. The most potent toxin, stagonolide H, indicated selectivity when tested on leaves of eight different plants: Canada thistle was most sensitive to the compound.

Stagonospora cirsii is a pathogen of Cirsium arvense, causing necrotic lesions on leaves of this noxious weed. The fungus produced toxic metabolites when grown in liquid culture. A new phytotoxin, named stagonolide, was isolated and characterized as (8R,9R)-8-hydroxy-7-oxo-9-propyl-5-nonen-9-olide by spectroscopic methods. Stagonolide was shown to be a nonhost-specific but selective phytotoxin. Leaves of C. arvense were most sensitive and leaves of tomato and pepper (both Solanaceae) were less sensitive to stagonolide, which was assayed at 5 x 10(-3) M, than other plants. Stagonolide assayed at 5 x 10(-6) M was demonstrated to be a strong inhibitor of root growth in seedlings of C. arvense and some other Asteraceae species. Seedlings growth in wheat and radish was much less affected by the toxin, and seedlings of cucumber were insensitive to it.

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 potential of the fungus Ascochyta sonchi as a mycoherbicide for the biocontrol of the perennial weeds Sonchus arvensis and Cirsium arvense that occur throughout temperate regions of the world is under evaluation. Ascosonchine, a newly discovered enol tautomer of 4-pyridylpyruvic acid with potential herbicidal properties, is the main phytotoxin produced by this fungus. A simple and sensitive method has been developed for the rapid quantitative analysis of ascosonchine based on HPLC with UV detection. The toxin content in culture filtrates of different strains of A. sonchi was measured. The strains tested produced up to 2.7 mg/L when grown in static conditions. Toxin production was compared with the virulence on the host plant of each strain to determine if the most virulent strains could be simply selected by choosing the best toxin producers. The results obtained do not support this approach. The same HPLC method was also applied to quantify toxin production under different fungal growth conditions, in order to achieve the highest toxin production. The most productive strain synthesised more than 8 mg/L when grown for 8 weeks in static conditions. Copyright © 2006 John Wiley & Sons, Ltd.