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Special Issue "Bioassay-Guided Isolation of Natural Products"

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A special issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: closed (28 February 2013)

Special Issue Editor

Guest Editor
Prof. Dr. Florence K. Gleason (Website)

Department of Plant Biology, University of Minnesota, 1445 Gortner Avenue, Saint Paul, MN 55108, USA
Interests: anti-bacterial compounds; cyanobacteria; herbicides; lactones; LC-MS; membrane disruptors photosystem II inhibitors; peptides

Special Issue Information

Dear Colleagues,

After suffering a twenty year decline, the field of natural products is currently assuming new prominence. Plants, animals, and microorganisms have always been a continual source of new and useful compounds. Modern analytical and genetic techniques have made it considerably easier to isolate and exploit these compounds for human uses such as antibiotics and pesticides. Bioassay-guided isolation is still the basic procedure for characterizing new natural products with defined biological activity. The most effective assays are rapid and specific. Microorganisms are usually the assay organism that best fits this description especially when attempting to isolate new antibiotics. The basic techniques of agar and broth assays can be enhanced by use of genetically modified test organisms to increase efficiency. Automated assays in microtiter plates allow the testing of large numbers of samples in a short time. Once a target compound has been tentatively identified, metabolomics techniques can be used to find the appropriate strain of producer and optimize production. Equipped with an array of sensitive and rapid assays and analytical methods, the natural product researcher is more prepared than ever to explore nature’s vast frontier of chemical wonders.

Prof. Dr. Florence K. Gleason
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed Open Access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs).

Published Papers (6 papers)

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Research

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Open AccessArticle Isolation, Structural Analyses and Biological Activity Assays against Chronic Lymphocytic Leukemia of Two Novel Cytochalasins — Sclerotionigrin A and B
Molecules 2014, 19(7), 9786-9797; doi:10.3390/molecules19079786
Received: 21 March 2014 / Revised: 24 June 2014 / Accepted: 2 July 2014 / Published: 8 July 2014
Cited by 2 | PDF Full-text (281 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Two new cytochalasins, sclerotionigrin A (1) and B (2) were isolated together with the known proxiphomin (3) from the filamentous fungus Aspergillus sclerotioniger. The structures and relative stereochemistry of 1 and 2 were determined based [...] Read more.
Two new cytochalasins, sclerotionigrin A (1) and B (2) were isolated together with the known proxiphomin (3) from the filamentous fungus Aspergillus sclerotioniger. The structures and relative stereochemistry of 1 and 2 were determined based on comparison with 3, and from extensive 1D and 2D NMR spectroscopic analysis, supported by high resolution mass spectrometry (HRMS). Compounds 2 and 3 displayed cytotoxic activity towards chronic lymphocytic leukemia cells in vitro, with 3 being the most active. Full article
(This article belongs to the Special Issue Bioassay-Guided Isolation of Natural Products)
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Open AccessArticle Bio-Activity and Dereplication-Based Discovery of Ophiobolins and Other Fungal Secondary Metabolites Targeting Leukemia Cells
Molecules 2013, 18(12), 14629-14650; doi:10.3390/molecules181214629
Received: 12 October 2013 / Revised: 15 November 2013 / Accepted: 21 November 2013 / Published: 26 November 2013
Cited by 7 | PDF Full-text (746 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
The purpose of this study was to identify and characterize fungal natural products (NPs) with in vitro bioactivity towards leukemia cells. We based our screening on a combined analytical and bio-guided approach of LC-DAD-HRMS dereplication, explorative solid-phase extraction (E-SPE), and a co-culture [...] Read more.
The purpose of this study was to identify and characterize fungal natural products (NPs) with in vitro bioactivity towards leukemia cells. We based our screening on a combined analytical and bio-guided approach of LC-DAD-HRMS dereplication, explorative solid-phase extraction (E-SPE), and a co-culture platform of CLL and stromal cells. A total of 289 fungal extracts were screened and we tracked the activity to single compounds in seven of the most active extracts. The novel ophiobolin U was isolated together with the known ophiobolins C, H, K as well as 6-epiophiobolins G, K and N from three fungal strains in the Aspergillus section Usti. Ophiobolins A, B, C and K displayed bioactivity towards leukemia cells with induction of apoptosis at nanomolar concentrations. The remaining ophiobolins were mainly inactive or only slightly active at micromolar concentrations. Dereplication of those ophiobolin derivatives possessing different activity in combination with structural analysis allowed a correlation of the chemical structure and conformation with the extent of bioactivity, identifying the hydroxy group at C3 and an aldehyde at C21, as well as the A/B-cis ring structure, as indispensible for the strong activity of the ophiobolins. The known compounds penicillic acid, viridicatumtoxin, calbistrin A, brefeldin A, emestrin A, and neosolaniol monoacetate were identified from the extracts and also found generally cytotoxic. Full article
(This article belongs to the Special Issue Bioassay-Guided Isolation of Natural Products)
Open AccessArticle Differential Growth Inhibitory Effects of Highly Oxygenated Guaianolides Isolated from the Middle Eastern Indigenous Plant Achillea falcata in HCT-116 Colorectal Cancer Cells
Molecules 2013, 18(7), 8275-8288; doi:10.3390/molecules18078275
Received: 21 May 2013 / Revised: 20 June 2013 / Accepted: 8 July 2013 / Published: 15 July 2013
Cited by 4 | PDF Full-text (297 KB) | HTML Full-text | XML Full-text
Abstract
Medicinal plants play a crucial role in traditional medicine and in the maintenance of human health worldwide. Sesquiterpene lactones represent an interesting group of plant-derived compounds that are currently being tested as lead drugs in cancer clinical trials. Achillea falcata is a [...] Read more.
Medicinal plants play a crucial role in traditional medicine and in the maintenance of human health worldwide. Sesquiterpene lactones represent an interesting group of plant-derived compounds that are currently being tested as lead drugs in cancer clinical trials. Achillea falcata is a medicinal plant indigenous to the Middle Eastern region and belongs to the Asteraceae family, which is known to be rich in sesquiterpene lactones. We subjected Achillea falcata extracts to bioassay-guided fractionation against the growth of HCT-116 colorectal cancer cells and identified four secotanapartholides, namely 3-β-methoxy- isosecotanapartholide (1), isosecotanapartholide (2), tanaphallin (3), and 8-hydroxy-3-methoxyisosecotanapartholide (4). Three highly oxygenated guaianolides were isolated for the first time from Achillea falcata, namely rupin A (5), chrysartemin B (6), and 1β, 2β-epoxy- 3β,4α,10α-trihydroxyguaian- 6α,12-olide (7). These sesquiterpene lactones showed no or minor cytotoxicity while exhibiting promising anticancer effects against HCT-116 cells. Further structure-activity relationship studies related the bioactivity of the tested compounds to their skeleton, their lipophilicity, and to the type of functional groups neighboring the main alkylating center of the molecule. Full article
(This article belongs to the Special Issue Bioassay-Guided Isolation of Natural Products)
Open AccessArticle The Use of Bio-Guided Fractionation to Explore the Use of Leftover Biomass in Dutch Flower Bulb Production as Allelochemicals against Weeds
Molecules 2013, 18(4), 4510-4525; doi:10.3390/molecules18044510
Received: 28 February 2013 / Revised: 28 March 2013 / Accepted: 12 April 2013 / Published: 17 April 2013
PDF Full-text (649 KB) | HTML Full-text | XML Full-text
Abstract
A major problem in flower bulb cultivation is weed control. Synthetic herbicides are mainly used, although they cause a range of problems, and integrated weed control through application of naturally occurring allelochemicals would be highly desirable. Flower bulb production creates large amounts [...] Read more.
A major problem in flower bulb cultivation is weed control. Synthetic herbicides are mainly used, although they cause a range of problems, and integrated weed control through application of naturally occurring allelochemicals would be highly desirable. Flower bulb production creates large amounts of leftover biomass. Utilizing this source for weed control may provide new applications of the bulb crops. We therefore screened 33 flower bulb extracts for allelochemical activity against weeds. Several methanol and chloroform extracts were observed to inhibit germination and growth of Senecio vulgaris L. and Lolium perenne L., as representatives of di- and mono-cotyledonous weeds, respectively. Narciclasine was identified as the bioactive compound in Narcissus. The extract of Amaryllis belladonna L. was equally active, but did not contain any narciclasine. Bioassay-guided fractionation of the A. belladonna extract resulted in the identification of lycorine as the bio-active compound. The IC50 measured for radicle growth inhibition was 0.10 µM for narciclasine and 0.93 µM for lycorine, compared to 0.11 mM of chlorpropham, a synthetic herbicide. Therefore, the leftover biomass from the spring bulb industry represents an interesting potential source for promising allelochemicals for further studies on weed growth inhibition. Full article
(This article belongs to the Special Issue Bioassay-Guided Isolation of Natural Products)
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Open AccessArticle Identification of Alternaria alternata Mycotoxins by LC-SPE-NMR and Their Cytotoxic Effects to Soybean (Glycine max) Cell Suspension Culture
Molecules 2013, 18(3), 2528-2538; doi:10.3390/molecules18032528
Received: 13 December 2012 / Revised: 29 January 2013 / Accepted: 16 February 2013 / Published: 26 February 2013
Cited by 2 | PDF Full-text (484 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
This present work describes the application of liquid chromatograpy-solid phase extraction-nuclear magnetic resonance spectroscopy to analyse Alternaria alternata crude extracts. Altenusin (1), alternariol (2), 3'-hydroxyalternariol monomethyl ether (3), and alternariol monomethyl ether (4), were [...] Read more.
This present work describes the application of liquid chromatograpy-solid phase extraction-nuclear magnetic resonance spectroscopy to analyse Alternaria alternata crude extracts. Altenusin (1), alternariol (2), 3'-hydroxyalternariol monomethyl ether (3), and alternariol monomethyl ether (4), were separated and identified. High-resolution mass spectrometry confirmed the proposed structures. The cytotoxic effects of these compounds towards plants were determined using soybean (Glycine max) cell cultures as a model. EC50 values which range from 0.11 (±0.02) to 4.69 (±0.47) μM showed the high cytotoxicity of these compounds. Full article
(This article belongs to the Special Issue Bioassay-Guided Isolation of Natural Products)
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Review

Jump to: Research

Open AccessReview Vasodilator Compounds Derived from Plants and Their Mechanisms of Action
Molecules 2013, 18(5), 5814-5857; doi:10.3390/molecules18055814
Received: 19 April 2013 / Revised: 24 April 2013 / Accepted: 7 May 2013 / Published: 17 May 2013
Cited by 6 | PDF Full-text (373 KB) | HTML Full-text | XML Full-text
Abstract
The present paper reviews vasodilator compounds isolated from plants that were reported in the past 22 years (1990 to 2012) and the different mechanisms of action involved in their vasodilator effects. The search for reports was conducted in a comprehensive manner, intending [...] Read more.
The present paper reviews vasodilator compounds isolated from plants that were reported in the past 22 years (1990 to 2012) and the different mechanisms of action involved in their vasodilator effects. The search for reports was conducted in a comprehensive manner, intending to encompass those metabolites with a vasodilator effect whose mechanism of action involved both vascular endothelium and arterial smooth muscle. The results obtained from our bibliographic search showed that over half of the isolated compounds have a mechanism of action involving the endothelium. Most of these bioactive metabolites cause vasodilation either by activating the nitric oxide/cGMP pathway or by blocking voltage-dependent calcium channels. Moreover, it was found that many compounds induced vasodilation by more than one mechanism. This review confirms that secondary metabolites, which include a significant group of compounds with extensive chemical diversity, are a valuable source of new pharmaceuticals useful for the treatment and prevention of cardiovascular diseases. Full article
(This article belongs to the Special Issue Bioassay-Guided Isolation of Natural Products)
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