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Environmental Health : a Global Access... Jun 2024Risk assessment (RA) of microbial secondary metabolites (SM) is part of the EU approval process for microbial active substances (AS) used in plant protection products... (Review)
Review
Risk assessment (RA) of microbial secondary metabolites (SM) is part of the EU approval process for microbial active substances (AS) used in plant protection products (PPP). As the number of potentially produced microbial SM may be high for a certain microbial strain and existing information on the metabolites often are low, data gaps are frequently identified during the RA. Often, RA cannot conclusively clarify the toxicological relevance of the individual substances. This work presents data and RA conclusions on four metabolites, Beauvericin, 2,3-deepoxy-2,3-didehydro-rhizoxin (DDR), Leucinostatin A and Swainsonin in detail as examples for the challenging process of RA. To overcome the problem of incomplete assessment reports, RA of microbial AS for PPP is in need of new approaches. In view of the Next Generation Risk Assessment (NGRA), the combination of literature data, omic-methods, in vitro and in silico methods combined in adverse outcome pathways (AOPs) can be used for an efficient and targeted identification and assessment of metabolites of concern (MoC).
Topics: Risk Assessment; European Union; Secondary Metabolism; Depsipeptides; Humans
PubMed: 38835048
DOI: 10.1186/s12940-024-01092-0 -
Cancer Research Sep 2000We describe a cell-based assay for antimitotic compounds that is suitable for drug discovery and for quantitative determination of antimitotic activity. In the assay,...
We describe a cell-based assay for antimitotic compounds that is suitable for drug discovery and for quantitative determination of antimitotic activity. In the assay, cells arrested in mitosis as a result of exposure to antimitotic agents in pure form or in crude natural extracts are detected by ELISA using the monoclonal antibody TG-3. The assay was used to screen >24,000 extracts of marine microorganisms and invertebrates and terrestrial plants and to guide the purification of active compounds from 5 of 119 positive extracts. A new rhizoxin analogue was found in a Pseudomonas species, six new eleutherobin analogues were identified from the octocoral Erythropodium caribaeorum, and two paclitaxel analogues were found in the stem bark of the tree Ilex macrophylla. The assay was also used for quantitative comparison of the antimitotic activity of different analogues. It revealed the importance of the C-11 to C-13 segment of the diterpene core of eleutherobin for its antimitotic activity. The identification of antimitotic compounds in very low abundance and their high (0.5%) occurrence in natural extracts indicates that drug discovery efforts using this cell-based assay may lead to the identification of structurally novel antimitotic agents.
Topics: Alkaloids; Animals; Antibiotics, Antineoplastic; Antineoplastic Agents; Antineoplastic Agents, Phytogenic; Breast Neoplasms; Diterpenes; Drug Screening Assays, Antitumor; Enzyme-Linked Immunosorbent Assay; Humans; Invertebrates; Lactones; Macrolides; Marine Biology; Paclitaxel; Plant Extracts; Plants, Medicinal; Pseudomonas; Structure-Activity Relationship; Tissue Extracts; Tumor Cells, Cultured
PubMed: 11016628
DOI: No ID Found -
Angewandte Chemie (International Ed. in... Sep 2012
Topics: Chromatography, High Pressure Liquid; Macrolides; Molecular Structure; Rhizopus
PubMed: 22915379
DOI: 10.1002/anie.201204540 -
Cancer Surveys 1993The five examples given here illustrate new cytotoxic agents at different stages of evaluation. In all cases, considerable effort has gone into detailed pharmacokinetic... (Review)
Review
The five examples given here illustrate new cytotoxic agents at different stages of evaluation. In all cases, considerable effort has gone into detailed pharmacokinetic studies conducted before and during the clinical phase I studies. Has this effort contributed significantly to the development of these agents? At present, it has to be said that the contribution made in the case of these particular agents has been modest. For the anthrapyrazoles, the availability of the pharmacokinetic data did not permit a pharmacokinetically guided dose escalation to be performed because of non-linear kinetics, and a similar comment can be made for rhizoxin, since the human plasma AUC values at the MTD were much lower than in the mouse. For the camptothecin analogues, a detailed knowledge of the kinetics of the closed and open forms of the various agents did not influence the way in which the studies were conducted, nor did pharmacokinetic information appreciably do so for EO9, although some comfort was gained by clinical investigators when the short half-life seen in preclinical species was also observed in humans. For suramin, therapeutic drug monitoring is clearly essential, although toxicity remains a problem. Of course, a proper understanding of the pharmacokinetics and metabolism of these agents greatly improves the interpretation of the clinical observations made and is often critical in planning the next stages of development. This is more clearly seen with agents that have unusual forms of toxicity, such as flavone acetic acid, for which the achievement of notional target concentrations is a key element in clinical trials (Kerr et al, 1987; Maughan et al, 1992). Moreover, as reviewed elsewhere (Graham and Workman, 1992; see also Graham and Kaye, this volume), there are several other instances where pharmacokinetically guided dose escalation has greatly improved the conduct of a phase I study. Good examples of this are iododoxorubicin (Gianni et al, 1990), mitotic inhibitor CI-980 (Brodfuehrer et al, 1992) and DNA intercalator CI-958 (Whitfield et al, 1992). Not surprisingly then, pharmacokinetics can help guide early clinical studies of some compounds but not others and whether they will be of value can only be determined by carrying out the pharmacokinetic measurements. The real value of the pharmacokinetic studies for the five compounds reviewed may not yet have been seen. Interpatient variations in drug handling can play a major part in determining levels of anti-tumour activity as well as toxicity.(ABSTRACT TRUNCATED AT 400 WORDS)
Topics: Animals; Anthracyclines; Antibiotics, Antineoplastic; Antineoplastic Agents; Aziridines; Camptothecin; Clinical Trials, Phase I as Topic; Humans; Indolequinones; Indoles; Irinotecan; Lactones; Macrolides; Neoplasms; Suramin; Topotecan
PubMed: 8137348
DOI: No ID Found -
Angewandte Chemie (International Ed. in... Jan 2001
PubMed: 11169722
DOI: No ID Found -
Environmental Microbiology Sep 2021The unicellular alga Chlamydomonas reinhardtii and the bacterium Pseudomonas protegens serve as a model to study the interactions between photosynthetic and...
The unicellular alga Chlamydomonas reinhardtii and the bacterium Pseudomonas protegens serve as a model to study the interactions between photosynthetic and heterotrophic microorganisms. P. protegens secretes the cyclic lipopeptide orfamide A that interferes with cytosolic Ca homeostasis in C. reinhardtii resulting in deflagellation of the algal cells. Here, we studied the roles of additional secondary metabolites secreted by P. protegens using individual compounds and co-cultivation of algae with bacterial mutants. Rhizoxin S2, pyrrolnitrin, pyoluteorin, 2,4-diacetylphloroglucinol (DAPG) and orfamide A all induce changes in cell morphology and inhibit the growth of C. reinhardtii. Rhizoxin S2 exerts the strongest growth inhibition, and its action depends on the spatial structure of the environment (agar versus liquid culture). Algal motility is unaffected by rhizoxin S2 and is most potently inhibited by orfamide A (IC = 4.1 μM). Pyrrolnitrin and pyoluteorin both interfere with algal cytosolic Ca homeostasis and motility whereas high concentrations of DAPG immobilize C. reinhardtii without deflagellation or disturbance of Ca homeostasis. Co-cultivation with a regulatory mutant of bacterial secondary metabolism (ΔgacA) promotes algal growth under spatially structured conditions. Our results reveal how a single soil bacterium uses an arsenal of secreted antialgal compounds with complementary and partially overlapping activities.
Topics: Chlamydomonas reinhardtii; Microalgae; Pseudomonas; Secondary Metabolism
PubMed: 34347373
DOI: 10.1111/1462-2920.15700 -
ELife Sep 2014Some of the proteins and enzymes that allow bacteria to enter living fungal cells and cause rice seedling blight have been identified.
Some of the proteins and enzymes that allow bacteria to enter living fungal cells and cause rice seedling blight have been identified.
Topics: Burkholderia; Macrolides; Rhizopus; Symbiosis
PubMed: 25268072
DOI: 10.7554/eLife.04603 -
Cancer Treatment Reviews Sep 1990
Review
Topics: Alkylating Agents; Animals; Antineoplastic Agents; Aziridines; Drug Screening Assays, Antitumor; Enzyme Inhibitors; Europe; Humans; Indolequinones; Indoles; Lactones; Macrolides; Mice; Nitrosourea Compounds; Organizations; Quinones
PubMed: 2272028
DOI: 10.1016/0305-7372(90)90035-e -
Yakugaku Zasshi : Journal of the... Apr 1998Microtubules (MT), composed of a protein tubulin (TN) alpha,beta-heterodimer with concomitant other proteins, microtubule associated proteins (MAPs and tau), are known... (Review)
Review
Microtubules (MT), composed of a protein tubulin (TN) alpha,beta-heterodimer with concomitant other proteins, microtubule associated proteins (MAPs and tau), are known to be the main component of spindles in a mitotic apparatus of eucaryotic cells, and are also involved in many other basic and essential cell functions. There are a number of natural and synthetic compounds that interfere with MT function to cause the mitotic arrest of eucaryotic cells. Such antimitotic agents show a broad biological activity, and can be used for medicinal and agrochemical purposes. On the other hand, they are also important as the biochemical tools for understanding the dynamics of MT network. Most of such antimitotic agents, with a few exceptions, bind to beta-TN. Among them, colchicine (CLC), vinblastine (VLB) and taxol have been of major importance in biochemical studies of MT and in studies of their intracellular functions. The former two both inhibit MT assembly but their binding sites on beta-TN are different; CLC-site and VLB-site, and many MT inhibitors bind to either sites. Taxol bind to TN at a site other than CLC-site and VLB-site, and promote MT assembly. We have worked on a variety of antimitotic agents that bind to CLC, VLB or taxol-site, in discoveries, structures, biological actions and/or interactions with TN. In this paper, I summarized the results of our studies on VLB-site ligands; (1) rhizoxin (RZX), isolated as a phytotoxin produced by a plant pathogenic fungus, and its related compounds, (2) derivatives of ansamitocin P-3 (ASMP3) (maytansinoid: MAY), isolated as a cytotoxic metabolite of an Actinomycete, (3) phomopsin A (PMSA), isolated as a mycotoxin produced by a plant parasitic fungus, (4) dolastatin 10 (DLS10), isolated as a cytotoxic metabolite of a see animal, (5) ustiloxins (USL) A-F, isolated as a mycotoxin produced by a plant pathogenic fungus, (6) arenastation A (ARSA), isolated as a cytotoxic metabolite of a sponge, and its synthetic analogs. From our studies on interactions of these VLB-site ligands with TN, we showed that the presence of a distinct RZX/MAY-binding site which only partially overlap with VLB-site, and that PMSA, DLS10, USLs and ARSA bind to the RZX/MAY site. RZX, ASMP3 and ARSA inhibit the growth of a variety of fungi, including Aspergillus nidulans. In order to obtain information as to the drug-TN interaction at the RZX/MAY site, RZX-resistant beta-TN gene mutants were isolated from RZX-sensitive wild-type A. nidulans. In all the beta-TN gene mutants, single amino acid (100th) alteration, asparagine-to-isoleucine, was observed. Sequence displacement experiments confirmed that this alteration conferred resistance to RZX and ASMP3, and also to ARSA. This resistance mechanism was further verified with yeasts Schizosaccharomyces pombe and Saccharomyces serevisiae. All the natural ligands mentioned above show potent cytotoxicity against human and murine tumor cells, but VLB, PMSA, DLS10 and USLA are inactive to both RZX-sensitive and -resistant fungal strains.
Topics: Animals; Antineoplastic Agents; Binding Sites; Fungi; Humans; Ligands; Microtubules; Mitosis; Molecular Conformation; Mutation; Neoplasms; Tubulin
PubMed: 9564789
DOI: No ID Found -
Biochemical Pharmacology Jun 1990Dolastatin 10, a cytostatic peptide containing several unique amino acid subunits, was isolated from the marine shell-less mollusk Dolabella auricularia (Pettit GR,... (Comparative Study)
Comparative Study
Dolastatin 10, a cytostatic peptide containing several unique amino acid subunits, was isolated from the marine shell-less mollusk Dolabella auricularia (Pettit GR, Kamano Y, Herald CL, Tuinman AA, Boettner FE, Kizu H, Schmidt JM, Baczynskyj L, Tomer KB and Bontems RJ, J Am Chem Soc 109: 6883-6885, 1987). Since our preliminary studies demonstrated that dolastatin 10 inhibited tubulin polymerization and the binding of radiolabeled vinblastine to tubulin, an initial characterization of the properties of dolastatin 10 included a comparison to other antimitotic drugs interfering with vinca alkaloid binding to tubulin (vinblastine, maytansine, rhizoxin, and phomopsin A). Dolastatin 10 inhibited the growth of L1210 murine leukemia cells in culture, with a concordant rise in the mitotic index, and its IC50 value for cell growth was 0.5 nM. Comparable values for the other drugs were 0.5 nM for maytansine, 1 nM for rhizoxin, 20 nM for vinblastine, and 7 microM for phomopsin A. IC50 values were also obtained for the polymerization of purified tubulin in glutamate: 1.2 microM for dolastatin 10, 1.4 microM for phomopsin A, 1.5 microM for vinblastine, 3.5 microM for maytansine, and 6.8 microM for rhizoxin. Dolastatin 10 and vinblastine were comparable in their effects on microtubule assembly dependent on microtubule-associated proteins. Preliminary studies indicated that dolastatin 10, like vinblastine, causes formation of a cold-stable tubulin aggregate at higher drug concentrations. We confirmed that rhizoxin, phomopsin A, and maytansine also inhibit the binding of radiolabeled vinblastine and vincristine to tubulin. Dolastatin 10 and phomopsin A were the strongest inhibitors of these reactions, and rhizoxin the weakest. Dolastatin 10, phomopsin A, maytansine, vinblastine, and rhizoxin all inhibited tubulin-dependent GTP hydrolysis. The greatest inhibition of hydrolysis was observed with dolastatin 10 and phomopsin A, and the least inhibition with rhizoxin.
Topics: Amino Acid Sequence; Animals; Antibiotics, Antineoplastic; Aziridines; Cell Division; Cell Survival; Depsipeptides; Diamines; Drug Interactions; Guanosine Triphosphate; Mice; Mitotic Index; Molecular Sequence Data; Oligopeptides; Organophosphorus Compounds; Thiazoles; Tubulin; Tumor Cells, Cultured; Vinca Alkaloids; Vincristine
PubMed: 2353935
DOI: 10.1016/0006-2952(90)90613-p