Secondary Metabolic Profiles Research Articles

Secondary metabolic profiling and antibacterial activities of different species of Usnea collected in Northern Philippines

Secondary metabolic profiling and antibacterial activities of different species of Usnea collected in Northern Philippines

Plant secondary metabolite profiling evidences strain-dependent effect in the Azospirillum–Oryza sativa association

Azospirillum is a plant growth-promoting rhizobacterium (PGPR) able to enhance growth and yield of cereals such as rice, maize and wheat. The growth-promoting ability of some Azospirillum strains appears to be highly specific to certain plant species and cultivars. In order to ascertain the specificity of the associative symbiosis between rice and Azospirillum, the physiological response of two rice cultivars, Nipponbare and Cigalon, inoculated with two rice-associated Azospirillum was analyzed at two levels: plant growth response and plant secondary metabolic response. Each strain of Azospirillum (Azospirillum lipoferum 4B isolated from Cigalon and Azospirillum sp. B510 isolated from Nipponbare) preferentially increased growth of the cultivar from which it was isolated. This specific effect is not related to a defect in colonization of host cultivar as each strain colonizes effectively both rice cultivars, either at the rhizoplane (for 4B and B510) and inside the roots (for B510). The metabolic profiling approach showed that, in response to PGPR inoculation, profiles of rice secondary metabolites were modified, with phenolic compounds such as flavonoids and hydroxycinnamic derivatives being the main metabolites affected. Moreover, plant metabolic changes differed according to Azospirillum strain×cultivar combinations; indeed, 4B induced major secondary metabolic profile modifications only on Cigalon roots, while B510, probably due to its endophytic feature, induced metabolic variations on shoots and roots of both cultivars, triggering a systemic response. Plant secondary metabolite profiling thereby evidences the specific interaction between an Azospirillum strain and its original host cultivar.

In vitro and in vivo antitumor activity of crude extracts obtained from Brazilian Chromobacterium sp isolates

Natural products produced by microorganisms have been an important source of new substances and lead compounds for the pharmaceutical industry. Chromobacterium violaceum is a Gram-negative β-proteobacterium, abundant in water and soil in tropical and subtropical regions and it produces violacein, a pigment that has shown great pharmaceutical potential. Crude extracts of five Brazilian isolates of Chromobacterium sp (0.25, 2.5, 25, and 250 µg/mL) were evaluated in an in vitro antitumor activity assay with nine human tumor cells. Secondary metabolic profiles were analyzed by liquid chromatography and electrospray ionization mass spectrometry resulting in the identification of violacein in all extracts, whereas FK228 was detected only in EtCE 308 and EtCE 592 extracts. AcCE and EtCE 310 extracts showed selectivity for NCI/ADR-RES cells in the in vitro assay and were evaluated in vivo in the solid Ehrlich tumor model, resulting in 50.3 and 54.6% growth inhibition, respectively. The crude extracts of Chromobacterium sp isolates showed potential and selective antitumor activities for certain human tumor cells, making them a potential source of lead compounds. Furthermore, the results suggest that other compounds, in addition to violacein, deoxyviolacein and FK228, may be involved in the antitumor effect observed.

Qualitative and quantitative analysis of phenylpropanoids in cell culture, regenerated plantlets and herbs of Saussurea involucrata

The major phenylpropanoids in the cell culture, regenerated plantlets and herbs of Saussurea involucrata were systematically and comparatively investigated. A total of 17 constituents were identified on the basis of HPLC-DAD/ESI-MSn and HPLC-ESI-IT-TOF/MS analyses. Among them, 13 constituents were unambiguously identified by comparing the retention time, UV, MS and MSn spectra of samples with standards/literature, and the other 4 constituents were tentatively assigned on the basis of their UV spectra and MSn fragmentation patterns. In addition, a quantification method for the simultaneous quantification of 3 major phenylpropanoids syringin, 5-caffeoylquinic acid, and 1,5-dicaffeoylquinic acid was successfully established. The established HPLC quantification method was proved to have excellent linearity, precision, repeatability and accuracy. These studies provide a secondary metabolic profile of the cell cultures of S. involucrata, which is valuable for improving the quality control of cell culture and sheds light on the biosynthetic pathway of phenylpropanoids in this species.

Comparison of prominent Azospirillum strains in Azospirillum–Pseudomonas–Glomus consortia for promotion of maize growth

Azospirillum are prominent plant growth-promoting rhizobacteria (PGPR) extensively used as phytostimulatory crop inoculants, but only few studies are dealing with Azospirillum-containing mixed inocula involving more than two microorganisms. We compared here three prominent Azospirillum strains as part of three-component consortia including also the PGPR Pseudomonas fluorescens F113 and a mycorrhizal inoculant mix composed of three Glomus strains. Inoculant colonization of maize was assessed by quantitative PCR, transcription of auxin synthesis gene ipdC (involved in phytostimulation) in Azospirillum by RT-PCR, and effects on maize by secondary metabolic profiling and shoot biomass measurements. Results showed that phytostimulation by all the three-component consortia was comparable, despite contrasted survival of the Azospirillum strains and different secondary metabolic responses of maize to inoculation. Unexpectedly, the presence of Azospirillum in the inoculum resulted in lower phytostimulation in comparison with the Pseudomonas-Glomus two-component consortium, but this effect was transient. Azospirillum's ipdC gene was transcribed in all treatments, especially with three-component consortia, but not with all plants and samplings. Inoculation had no negative impact on the prevalence of mycorrhizal taxa in roots. In conclusion, this study brought new insights in the functioning of microbial consortia and showed that Azospirillum-Pseudomonas-Glomus three-component inoculants may be useful in environmental biotechnology for maize growth promotion.

A new aminopeptidase inhibitor from Streptomyces strain HCCB10043 found by UPLC–MS

The diversity of microbial metabolites has been of interest and concern for a long time, yet a suitable method for discovering these is still unavailable. In the work discussed in this report, ultra-performance liquid chromatography coupled with tandem quadrupole and time of flight high-resolution mass spectrometry (UPLC-Q-TOF-HRMS), with MS data analysis, was set up to study the metabolites of Streptomyces strain HCCB10043. It was found that besides antibacterial substances (A21978C complex) and two anti-aminopeptidase compounds (valistatin and bestatin), this strain can produce a new aminopeptidase inhibitor, identified as 3-amino-2-hydroxy-4-phenylbutanoylvalylisoleucine. This new compound had greater activity than valistatin or bestatin in aminopeptidase N (APN) inhibition assay. The results proved that combination of UPLC-Q-TOF-MS analysis and classic purification and identification steps as complementary strategies can provide a method with high reliability for research on microbial secondary metabolites. Furthermore, it has shown that the study of secondary metabolic profiling might be the key to discovering new drugs.

Secondary metabolite profiling of the model legume Lotus japonicus during its symbiotic interaction with Mesorhizobium loti

Plant secondary metabolites, particularly flavonoids, are key components in the early stages of nitrogen-fixing symbiosis. Despite their importance, the endogenous secondary metabolites involved in symbiosis have not yet been identified in the model legume Lotus japonicus. We therefore determined changes in the secondary metabolic profile of Lotus japonicus roots in response to its symbiont. Analysis of the root secondary metabolite profiles 1 week after inoculation with Mesorhizobium loti revealed quantitative changes in the level of 14 phenolic peaks when compared with non-inoculated control plants. These changes affected compounds from most phenolic classes, possibly resulting from interconversion between classes since the total phenolic level remained constant. In addition, the use of 2 M. loti strains differing only in their capacity to synthesise Nod factor revealed that, although Nod factor signalling induced accumulation of a specific subset of 4 phenolic peaks, most changes were induced in response to both rhizobial strains.

Interactions between arthropod-induced aboveground and belowground defenses in plants.

Plants can be attacked by arthropods both above and below ground. The ensuing systemic defense response of the plant can affect even the most distant tissues. Both primary and secondary metabolic profiles of shoots can be altered upon root herbivory and vice versa ([Gange and Brown, 1989][1]; [

Establishing inhibitory concentrations of novel formamide fungicides on fungi pertinent to medicine and agriculture

Formamides are a novel group of anti-fungal drugs discovered by Bobylev et al. Formamides were designed as analogs of triazole fungicides where the triazolyl moiety is replaced with the formamide moiety. Despite being analogs, formamide fungicides differ from triazole fungicides in their biochemical mode of action. Specifically, it was found that the lead candidate N-[1-(2,4-dichlorophenyl)-4,4-dimethylpent-1-en-3-yl] formamide (I) did not affect the sterol composition of fungi that were grown in the presence of inhibitory concentrations of I. The site and mechanism of the anti-fungal action of novel formamide fungicides remains unknown. One of the ways to determine the biochemical mode of action of a new fungicide is to investigate the changes in secondary metabolite production by the affected organisms. In this work, inhibitory concentrations were established against a number of medicinal and agricultural fungal pathogens. These concentrations will be used in future projects to determine the changes in the secondary metabolic profiles of the affected fungi and ultimately to determine the biochemical mode of action of novel formamide fungicides. Development of fungicides that target different modes of action is vital to overcoming anti-fungal resistance. The project is supported by NIH grant P20 RR016741 from the NCRR.

Effect of Elm Selection, Explant Source and Medium Composition on Growth of Ophiostoma ulmi on Callus Cultures

Abstract We examined the effects of elm selection, explant source and media composition on growth of the Dutch elm disease (DED) fungus Ophiostoma ulmi on callus cultures. Calluses were generated from leaf and stem tissue of an American elm (Ulmus Americana L.) seedling (A), susceptible to the disease; an American elm selection 8630, resistant to the disease; and a Siberian elm (U. pumila L.) seedling, also resistant to DED. Calluses were generated on modified Murashige-Skoog (MMS) medium, either with (MMSC) or without coconut milk. Explant source did not affect the fungal growth rate on the callus. Rate of O. ulmi growth on American elm A callus was similar on both media; on Siberian and 8630, fungal growth rate was more rapid on callus cultured on MMS than on MMSC. However, in the absence of callus tissue, O. ulmi growth on MMSC medium was more than five times as rapid as it was on MMS. We observed significant interactions between explant source and selection, and between medium and selection. Fungal growth was always more rapid on American A, and American 8630 then on Siberian. Scanning electron microscopy revealed heavy fungal sporulation on American A, slight on Siberian and none on American 8630. High performance liquid chromatography analysis showed that the secondary metabolic profiles were distinguishable for callus tissue versus explant tissue, but were similar for calli generated from different explant sources.