Secondary metabolites produced by a root-inhabiting sterile fungus antagonistic towards pathogenic fungi.

AIMS: A sterile red fungus (SRF) isolated from cortices of roots of both wheat (Triticum aestivum cv. Gamenya) and ryegrass (Lolium rigidum cv. Wimmera) was found to protect the hosts from phytopathogens and promote plant growth. In this work, the major secondary metabolites produced by this SRF were analysed, and their antibiotic and plant-growth-promoting activities investigated. METHODS AND RESULTS: Two main compounds, veratryl alcohol (VA) and 4-(hydroxymethyl)-quinoline, were isolated from the culture filtrate of the fungus. In antifungal assays, VA inhibited the growth of Sclerotinia sclerotiorum and Pythium irregulare even at low amounts, while high concentrations (>100 microg per plug) of 4-(hydroxymethyl)-quinoline were needed. Both metabolites revealed weak inhibition of Rhizoctonia solani. Furthermore, both compounds showed a growth promotion activity on canola (Brassica napus) seedlings used as bioassays. CONCLUSIONS: Isolation and characterization of the main secondary metabolites from culture filtrates of a root-inhabiting sterile fungus are reported. The biological assays indicate that these secondary metabolites may have a role in both plant growth regulation and antifungal activity. SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides a better understanding of the metabolism of a cortical fungus that may have a useful role in the biological suppression of root-infecting soil-borne plant pathogens.

Factors affecting the production of Trichoderma harzianum secondary metabolites during the interaction with different plant pathogens.

AIMS: Strains of Trichoderma spp. produce numerous bioactive secondary metabolites. The in vitro production and antibiotic activities of the major compounds synthesized by Trichoderma harzianum strains T22 and T39 against Leptosphaeria maculans, Phytophthora cinnamomi and Botrytis cinerea were evaluated. Moreover, the eliciting effect of viable or nonviable biomasses of Rhizoctonia solani, Pythium ultimum or B. cinerea on the in vitro production of these metabolites was also investigated. METHODS AND RESULTS: T22azaphilone, 1-hydroxy-3-methyl-anthraquinone, 1,8-dihydroxy-3-methyl-anthraquinone, T39butenolide, harzianolide, harzianopyridone were purified, characterized and used as standards. In antifungal assays, T22azaphilone and harzianopyridone inhibited the growth of the pathogens tested even at low doses (1-10 microg per plug), while high concentrations of T39butenolide and harzianolide were needed (>100 microg per plug) for inhibition. The in vitro accumulation of these metabolites was quantified by LC/MS. T22azaphilone production was not enhanced by the presence of the tested pathogens, despite its antibiotic activity. On the other hand, the anthraquinones, which showed no pathogen inhibition, were stimulated by the presence of P. ultimum. The production of T39butenolide was significantly enhanced by co-cultivation with R. solani or B. cinerea. Similarly, viable and nonviable biomasses of R. solani or B. cinerea increased the accumulation of harzianopyridone. Finally, harzianolide was not detected in any of the interactions examined. CONCLUSIONS: The secondary metabolites analysed in this study showed different levels of antibiotic activity. Their production in vitro varied in relation to: (i) the specific compound; (ii) the phytopathogen used for the elicitation; (iii) the viability of the elicitor; and (iv) the balance between elicited biosynthesis and biotransformation rates. SIGNIFICANCE AND IMPACT OF THE STUDY: The use of cultures of phytopathogens to enhance yields of Trichoderma metabolites could improve the production and application of novel biopesticides and biofertilizers based on the active compounds instead of the living microbe. This could have a significant beneficial impact on the management of diseases in crop plants.

Major secondary metabolites produced by two commercial Trichoderma strains active against different phytopathogens.

AIMS: Trichoderma harzianum strains T22 and T39 are two micro-organisms used as active agents in a variety of commercial biopesticides and biofertilizers and widely applied amongst field and greenhouse crops. The production, isolation, biological and chemical characterization of the main secondary metabolites produced by these strains are investigated. METHODS AND RESULTS: Of the three major compounds produced by strain T22, one is a new azaphilone that shows marked in vitro inhibition of Rhizoctonia solani, Pythium ultimum and Gaeumannomyces graminis var. tritici. In turn, filtrates from strain T39 were demonstrated to contain two compounds previously isolated from other T. harzianum strains and a new butenolide. The production of the isolated metabolites was also monitored by liquid chromatography/mass spectrometry during in vitro interaction with R. solani. CONCLUSIONS: This paper reports the isolation and characterization of the main secondary metabolites obtained from culture filtrates of two T. harzianum strains and their production during antagonistic interaction with the pathogen R. solani. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first work on secondary metabolites produced by the commercially applied strains T22 and T39. Our results provide a better understanding of the metabolism of these fungi, which are both widely used as biopesticides and/or biofertilizers in biocontrol.

Chemical defenses of Trifolium glanduliferum against redlegged earth mite Halotydeus destructor.

Trifolium glanduliferum Boiss. was resistant to redlegged earth mite, Halotydeus destructor Tucker (Acari: Penthaleidae), feeding compared with Trifolium subterraneum L. Extracts from T. glanduliferum leaves, obtained with dichloromethane and methanol, acted as feeding deterrents to the redlegged earth mite. Bioassay-directed fractionation of the extracts led to the isolation of several metabolites, coumarin, alpha-and beta-ionone, linalool, medicarpin, that were shown to be deterrent in laboratory experiments. The compounds contributing to the defense of T. glanduliferum were different from those influencing mite feeding on T. subterraneum leaves.

Production of leucinostatins and nematicidal activity of Australian isolates of Paecilomyces lilacinus (Thom) Samson.

AIMS: To evaluate the relationship between leucinostatin production by Paecilomyces lilacinus isolates and their biological activities. METHODS AND RESULTS: The nematicidal, parasitic and enzymatic activity of Australian P. lilacinus isolates were investigated. Nematicidal activities of culture filtrates were measured by mortality and inhibition of reproduction of Caenorhabditis elegans, whereas egg-parasitic activity was measured by colonization on Meloidogyne javanica. Enzymatic activities (protease and chitinase) were assayed on solid media. The results suggest that leucinostatins in P. lilacinus are indicators of nematicidal activity, whereas chitinase activity might be related to parasitism. CONCLUSIONS: Nematicidal activity of culture filtrates of Paecilomyces lilacinus strains related to their ability to produce leucinostatins. SIGNIFICANCE AND IMPACT OF THE STUDY: This is the first study describing the leucinostatins as nematicides.

Pathogenesis of Streptoverticillium albireticuli on Caenorhabditis elegans and its antagonism to soil-borne fungal pathogens.

AIMS: To examine the biological activity of Streptoverticillium albireticuli. METHODS: Isolation of S. albireticuli was carried out using the dry-heat technique. Nematicidal and pathogenic activity on Caenorhabditis elegans was measured by mortality in metabolites and colonization rate on fishmeal extract agar. Antifungal and enzymatic activities of S. albireticuli were measured by the agar plate method and the semidefined solid media method, respectively. RESULTS: S. albireticuli showed strong nematicidal activity against C. elegans. Pathogenic activity was also evident with the colonized nematode by the isolate on fishmeal extract agar. It also showed antifungal activity against certain fungal pathogens such as Rhizoctonia solani, Phytophthora cinnamomi and Fusarium oxysporum. SIGNIFICANCE AND IMPACT OF THE STUDY: The discovery of an actinomycete showing pathogenic activity against the nematode may indicate the potential for it to be used as a biocontrol agent of parasitic nematodes, in addition to its ability to suppress fungal pathogens.

Artoindonesianins G-I, three new isoprenylated flavones from Artocarpus lanceifolius.

Three new isoprenylated flavones, artoindonesianins G-I (1-3), together with the two known flavones artelastofuran (4) and artelasticin (5), have been isolated from the heartwood of Artocarpus lanceifoliu. The structures of the new compounds were determined on the basis of spectroscopic data. Compounds 1-3 and 5 showed strong cytotoxicity against P-388 cells.

Structure revision and assignment of absolute stereochemistry of a marine C21 bisfuranoterpene.

The C21 bisfuranoterpene (-)-isotetradehydrofurospongin-1 (6), previously isolated from a Western Australian Spongia sp., has been reisolated from a specimen of Spirastrella papilosa collected during scientific trawling operations in the Great Australian Bight. A 2D NMR analysis of 6 has prompted reassignment of the published structure 5, while degradation and chiral HPLC analysis have allowed determination of the absolute stereochemistry.

Isolation and structural identification of a germination inhibitor in fire-recruiters from the California chaparral.

A role for inhibitors as regulators of seed dormancy in fire-dependent annuals and their nondormant (fire-independent) congeners was examined in the family Hydrophyllaceae. From seeds of the fire-dependent species, Emmenanthe penduliflora, Phacelia minor, P. brachyloba, and P. grandiflora, extracts were obtained that were found to be largely self-inhibitory and potent inhibitors of seed germination in nondormant congeners. Lower activity was detected in the fire-independent species, P. tanacetifolia and P. campanularia. The inhibitory activity was associated with the new sucrose ester, 6-O-linoleyl-alpha-D-glucopyranosyl-beta-D-fructofuranoside.

Andalasin A, a new stilbene dimer from Morus macroura.

A new stilbene dimer, andalasin A (1), together with the known stilbene oxyresveratrol and the 2-arylbenzofuran glycoside mulberroside C, have been isolated from the wood of Morus macroura. The structure of the new compound was elucidated on the basis of spectroscopic data. Compound 1 shows weak antinematodal and moderate antifungal properties.

Lantana camara L. (Verbenaceae).

Lantana camara L. is regarded both as a notorious weed and a popular ornamental garden plant and has found various uses in folk medicine in many parts of the world. Some taxa of the widely variable L. camara complex are toxic to small ruminants and this effect has been associated with the types and relative amounts of some triterpene ester metabolites. However, L. camara also produces a number of metabolites in good yields and some have been shown to possess useful biological activities. All these aspects are considered in this review to allow an evaluation of the potential for utilisation of the large biomass of Lantana available. The phytochemistry of other members of the Lantana genus is included.

Mechanism of action of verbascoside on the isolated rat heart: increases in level of prostacyclin.

The mechanism of the positive cardioactive effects induced by verbascoside in the Lagendorff rat heart has been investigated. Isolated rat hearts treated with alpha- or beta-adrenergic agents did not show significant reduction of the positive chronotropism, inotropism and increased coronary perfusion rate mediated by verbascoside. A significant increase in prostacyclin levels (142%) observed following the administration of verbascoside suggests that prostacyclin stimulates formation of cAMP which induces the cardioactivity associated with verbascoside.

Artoindonesianins A and B, two new prenylated flavones from the root of Artocarpus champeden.

Two new prenylated flavones, named artoindonesianin A (1) and artoindonesianin B (2), were isolated from the root of Artocarpus champeden, together with a known prenylated flavone, artonin A. The structures of artoindonesianins A and B were determined on the basis of spectral evidence (MS, 1H and 13C NMR) and by comparison with known related compounds. Compounds 1 and 2 exhibited cytotoxic activity against murine leukemia (P-388) cells.

Biological and pharmacological activity of naturally occurring iridoids and secoiridoids.

The biological and pharmacological activities reported for naturally occurring iridoids and secoiridoids are reviewed. The hypothesis that iridoid glycoside and acetal esters can best be considered as pro-drugs and that corresponding hemiacetals and compounds derived from them carry the pharmacophores is discussed. The possibility that the activity of some iridoids is determined by their conversion to pyridine monoterpene alkaloids (PMTA) is also considered. The evidence available suggests that iridoids show activities consistent with those presented by immunomodulators and adaptogens.

Cardiovascular activity of naturally occurring lignans.

The activities of lignans and neolignans which directly or indirectly affect the cardiovascular system are reviewed. The results from molecular screening methods and animal models are included and an attempt to identify the molecular features which might influence some of the activities is made. The question of the benefit of low levels of circulating lignans in an organism is considered.

Cardioactive iridoid glycosides from Eremophila species.

Four iridoid glycosides isolated from different species of Eremophila (Myoporaceae) were tested for their effects on the Langendorff rat heart. Melampyroside (1), verminoside (2), ferruloylajugol (3) and catalpol (4) all significantly decreased contractile force in the isolated rat heart test. Within a minute after administration all, except catalpol, significantly increased heart rate and coronary perfusion rate. These results are compared to those of other cardioactive iridoid glycosides described in the literature.

Cardioactive compounds from Eremophila species.

The isolation and identification of two cardioactive compounds from two Eremophila species (Myoporaceae) considered important in the pharmacopoeia of the Australian Aboriginal people is described. Verbascoside, isolated from the methanol and water extracts of E. alternifolia leaves, mediated significant increases in chronotropism, inotropism and coronary perfusion rate (CPR) in the Langendorff rat heart. Geniposidic acid, isolated from the methanol extract of E. longifolia leaves, mediated an inhibitory effect with significant negative chronotropism, negative inotropism and CPR.

Molecular structure of terrecyclodiol: a derivative of the antifungal metabolite terrecyclic acid A from Aspergillus terreus.

A strain of Aspergillus terreus, which was isolated from organic mulch and inhibited the growth of the plant pathogen Phytophthora cinnamomi, produces an antifungal metabolite when grown in liquid culture. This metabolite was isolated by bioassay-guided fractionation and identified as terrecyclic acid A (1). X-ray diffraction studies and spectroscopic details of the derived terrecyclodiol (2) are described.

Bioactive acylphloroglucinol derivatives from Eucalyptus species.

The acyphloroglucinol derivatives produced by Eucalyptus species are reviewed. Aspects of their chemistry, stereochemistry, biological activity and biogenesis are discussed.