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Special Issue "Marine Natural Products - Advances in Separation, Characterisation and Chemical Profiling Methodologies"

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A special issue of Marine Drugs (ISSN 1660-3397).

Deadline for manuscript submissions: closed (30 November 2014)

Special Issue Editor

Guest Editor
Dr. Sylvia Urban

School of Applied Sciences (Applied Chemistry), RMIT University (City Campus), GPO Box 2476V, Melbourne 3001, Victoria, Australia
Website1 | Website2 | Website3 | E-Mail
Phone: +61 3 9925 3376
Fax: +61 3 9925 3747
Interests: marine and terrestrial natural products chemistry; isolation and structural characterization; NMR spectroscopy; analytical separation methodologies

Special Issue Information

Dear Colleagues

The search for bioactive secondary metabolites from marine organisms continues to be an active area of research in the drug discovery area. There is an ever demanding need to employ various chemical profiling strategies to accelerate the process of new compound discovery. This special issue of Marine Drugs will highlight advances in extraction, isolation, purification and dereplication methodologies which can expedite the search for bioactive marine natural products.

Dr. Sylvia Urban
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. Marine Drugs 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).

Keywords

  • hyphenated technologies;
  • hplc-nmr;
  • hplc-ms;
  • dereplication, extraction methodologies

Published Papers (12 papers)

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Research

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Open AccessArticle Dereplication and Chemotaxonomical Studies of Marine Algae of the Ochrophyta and Rhodophyta Phyla
Mar. Drugs 2015, 13(5), 2714-2731; doi:10.3390/md13052714
Received: 6 March 2015 / Revised: 9 April 2015 / Accepted: 21 April 2015 / Published: 30 April 2015
Cited by 1 | PDF Full-text (523 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Dereplication and chemotaxonomic studies of six marine algae of the Ochrophyta and one of the Rhodophyta phyla resulted in the detection of 22 separate compounds. All 16 secondary metabolites, including four new compounds (1619), could be rapidly dereplicated using
[...] Read more.
Dereplication and chemotaxonomic studies of six marine algae of the Ochrophyta and one of the Rhodophyta phyla resulted in the detection of 22 separate compounds. All 16 secondary metabolites, including four new compounds (1619), could be rapidly dereplicated using HPLC-NMR and HPLC-MS methodologies in conjunction with the MarinLit database. This study highlights the advantages of using NMR data (acquired via HPLC-NMR) for database searching and for the overall dereplication of natural products. Full article
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Open AccessArticle New Prenylated Aeruginosin, Microphycin, Anabaenopeptin and Micropeptin Analogues from a Microcystis Bloom Material Collected in Kibbutz Kfar Blum, Israel
Mar. Drugs 2015, 13(4), 2347-2375; doi:10.3390/md13042347
Received: 23 November 2014 / Revised: 16 March 2015 / Accepted: 18 March 2015 / Published: 15 April 2015
Cited by 1 | PDF Full-text (1078 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Thirteen new and eighteen known natural products were isolated from a bloom material of an assembly of various Microcystis spp. collected in November, 2008, from a commercial fishpond near Kibbutz Kfar Blum, the Jordan Valley, Israel. The new natural products included the prenylated
[...] Read more.
Thirteen new and eighteen known natural products were isolated from a bloom material of an assembly of various Microcystis spp. collected in November, 2008, from a commercial fishpond near Kibbutz Kfar Blum, the Jordan Valley, Israel. The new natural products included the prenylated aeruginosin KB676 (1), microphycin KB921 (2), anabaenopeptins KB906 (3) and KB899 (4) and micropeptins KB928 (5), KB956 (6), KB970A (7), KB970B (8), KB984 (9), KB970C (10), KB1048 (11), KB992 (12) and KB1046 (13). Their structures were elucidated primarily by interpretation of their 1D and 2D nuclear magnetic resonance spectra and high-resolution mass spectrometry. Marfey’s and chiral-phase high performance liquid chromatography methods were used to determine the absolute configurations of their chiral centers. Aeruginosin KB676 (1) contains the rare (2S,3aS,6S,7aS)-Choi and is the first prenylated aeruginosin derivative described in the literature. Compounds 1 and 511 inhibited trypsin with sub-μM IC50s, while Compounds 1113 inhibited chymotrypsin with sub-μM IC50s. The structures and biological activities of the new natural products and our procedures of dereplication are described. Full article
Open AccessCommunication Solvent Separating Secondary Metabolites Directly from Biosynthetic Tissue for Surface-Assisted Laser Desorption Ionisation Mass Spectrometry
Mar. Drugs 2015, 13(3), 1410-1431; doi:10.3390/md13031410
Received: 30 November 2014 / Revised: 13 February 2015 / Accepted: 2 March 2015 / Published: 16 March 2015
Cited by 2 | PDF Full-text (926 KB) | HTML Full-text | XML Full-text
Abstract
Marine bioactive metabolites are often heterogeneously expressed in tissues both spatially and over time. Therefore, traditional solvent extraction methods benefit from an understanding of the in situ sites of biosynthesis and storage to deal with heterogeneity and maximize yield. Recently, surface-assisted mass spectrometry
[...] Read more.
Marine bioactive metabolites are often heterogeneously expressed in tissues both spatially and over time. Therefore, traditional solvent extraction methods benefit from an understanding of the in situ sites of biosynthesis and storage to deal with heterogeneity and maximize yield. Recently, surface-assisted mass spectrometry (MS) methods namely nanostructure-assisted laser desorption ionisation (NALDI) and desorption ionisation on porous silicon (DIOS) surfaces have been developed to enable the direct detection of low molecular weight metabolites. Since direct tissue NALDI-MS or DIOS-MS produce complex spectra due to the wide variety of other metabolites and fragments present in the low mass range, we report here the use of “on surface” solvent separation directly from mollusc tissue onto nanostructured surfaces for MS analysis, as a mechanism for simplifying data annotation and detecting possible artefacts from compound delocalization during the preparative steps. Water, ethanol, chloroform and hexane selectively extracted a range of choline esters, brominated indoles and lipids from Dicathais orbita hypobranchial tissue imprints. These compounds could be quantified on the nanostructured surfaces by comparison to standard curves generated from the pure compounds. Surface-assisted MS could have broad utility for detecting a broad range of secondary metabolites in complex marine tissue samples. Full article
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Open AccessArticle Preparative Separation of Sulfur-Containing Diketopiperazines from Marine Fungus Cladosporium sp. Using High-Speed Counter-Current Chromatography in Stepwise Elution Mode
Mar. Drugs 2015, 13(1), 354-365; doi:10.3390/md13010354
Received: 14 October 2014 / Accepted: 1 January 2015 / Published: 9 January 2015
Cited by 3 | PDF Full-text (804 KB) | HTML Full-text | XML Full-text
Abstract
High-speed counter-current chromatography (HSCCC) was successively applied to the separation of three sulfur-containing diketopiperazines (DKPs) (including two new compounds cladosporin A (1) and cladosporin B (3), and a known compound haematocin (2)) from a marine fungus Cladosporium
[...] Read more.
High-speed counter-current chromatography (HSCCC) was successively applied to the separation of three sulfur-containing diketopiperazines (DKPs) (including two new compounds cladosporin A (1) and cladosporin B (3), and a known compound haematocin (2)) from a marine fungus Cladosporium sp. The two-phase solvent system composed of n-hexane-ethyl acetate-methanol-water at (1:1:1:1, v/v) and (2:1:2:1, v/v), in stepwise elution mode, was used for HSCCC. The preparative HSCCC separation was performed on 300 mg of crude sample yielding 26.7 mg of compound 3 at a purity of over 95%, 53.6 mg of a mixture of compounds 1 and 2, which was further separated by preparative-HPLC yielding 14.3 mg of compound 1 and 25.4 mg of compound 2 each at a purity of over 95%. Their structures were established by spectroscopic methods. The sulfur-containing DKPs suppressed the proliferation of hepatocellular carcinoma cell line HepG2. The present work represents the first application of HSCCC in the efficient preparation of marine fungal natural products. Full article
Open AccessArticle Total Synthesis of Gobiusxanthin Stereoisomers and Their Application to Determination of Absolute Configurations of Natural Products: Revision of Reported Absolute Configuration of Epigobiusxanthin
Mar. Drugs 2015, 13(1), 159-172; doi:10.3390/md13010159
Received: 4 December 2014 / Accepted: 22 December 2014 / Published: 30 December 2014
PDF Full-text (693 KB) | HTML Full-text | XML Full-text
Abstract
(3R)-Gobiusxanthin stereoisomers (1ad) were synthesized by stereoselective Wittig reaction of the (3R)-C15-acetylenic tri-n-butylphosphonium salt 7 with C25-apocarotenal stereoisomers 5a,b and 14a,b bearing four kinds of
[...] Read more.
(3R)-Gobiusxanthin stereoisomers (1ad) were synthesized by stereoselective Wittig reaction of the (3R)-C15-acetylenic tri-n-butylphosphonium salt 7 with C25-apocarotenal stereoisomers 5a,b and 14a,b bearing four kinds of 3,6-dihydroxy-ε-end groups. The validity of the reported stereochemistry of gobiusxanthin was demonstrated by the fact that the reported spectral data of natural gobiusxanthin were in agreement with those of synthetic (3R,3'S,6'R)-gobiusxanthin (1a). On the other hand, the reported CD spectral data of natural epigobiusxanthin, which has been assigned as (3R,3'R,6'R)-isomer (3'-epigobiusxanthin), were identical with those of synthetic (3R,3'S,6'S)-isomer 1d (6'-epigobiusxanthin) rather than those of the corresponding synthetic 3'-epi-isomer 1b. It was found that the stereochemistry at C3-position has little effect on the shape of their CD spectra. Thus, in order to reinforce the validity of the absolute configurations at C3-position of natural specimens, (3S,3'S,6'R)- and (3S,3'S,6'S)-stereoisomers 1e and 1f were also synthesized and a HPLC analytical method for four stereoisomers was established by using a column carrying a chiral stationary phase. The HPLC analysis has proven that the stereochemistry of the natural epigobiusxanthin is 3R,3'S,6'S. Full article
Open AccessArticle Chemical Profiling (HPLC-NMR & HPLC-MS), Isolation, and Identification of Bioactive Meroditerpenoids from the Southern Australian Marine Brown Alga Sargassum paradoxum
Mar. Drugs 2015, 13(1), 102-127; doi:10.3390/md13010102
Received: 7 November 2014 / Accepted: 15 December 2014 / Published: 29 December 2014
Cited by 4 | PDF Full-text (962 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
A phytochemical investigation of a southern Australian marine brown alga, Sargassum paradoxum, resulted in the isolation and identification of four new (5, 9, 10, and 15) and nine previously reported (1, 2, 6
[...] Read more.
A phytochemical investigation of a southern Australian marine brown alga, Sargassum paradoxum, resulted in the isolation and identification of four new (5, 9, 10, and 15) and nine previously reported (1, 2, 68, and 1114) bioactive meroditerpenoids. HPLC-NMR and HPLC-MS were central to the identification of a new unstable compound, sargahydroquinal (9), and pivotal in the deconvolution of eight (1, 2, 57, and 1012) other meroditerpenoids. In particular, the complete characterization and identification of the two main constituents (1 and 2) in the crude dichloromethane extract was achieved using stop-flow HPLC-NMR and HPLC-MS. This study resulted in the first acquisition of gHMBCAD NMR spectra in the stop-flow HPLC-NMR mode for a system solely equipped with a 60 μL HPLC-NMR flow cell without the use of a cold probe, microcoil, or any pre-concentration. Full article
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Open AccessArticle Five New Secondary Metabolites Produced by a Marine-Associated Fungus, Daldinia eschscholzii
Mar. Drugs 2014, 12(11), 5563-5575; doi:10.3390/md12115563
Received: 16 October 2014 / Revised: 12 November 2014 / Accepted: 13 November 2014 / Published: 20 November 2014
Cited by 2 | PDF Full-text (799 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Five new compounds, including a benzopyran ribonic glycoside, daldiniside A (1), two isocoumarin ribonic glycosides, daldinisides B (2) and C (3), and two alkaloids, 1-(3-indolyl)-2R,3-dihydroxypropan-1-one (4) and 3-ethyl-2, 5-pyrazinedipropanoic acid (5),
[...] Read more.
Five new compounds, including a benzopyran ribonic glycoside, daldiniside A (1), two isocoumarin ribonic glycosides, daldinisides B (2) and C (3), and two alkaloids, 1-(3-indolyl)-2R,3-dihydroxypropan-1-one (4) and 3-ethyl-2, 5-pyrazinedipropanoic acid (5), along with five known compounds (610), were isolated from the EtOAc extract of the marine-associated fungus, Daldinia eschscholzii. Their structures were elucidated by extensive physicochemical and spectroscopic properties, besides comparison with literature data. The absolute configurations of compounds 13 were corroborated by chemical transformation, GC analysis and X-ray crystallographic analysis. Meanwhile, the absolute configuration of compound 4 and the planar structure of compound 6 were also determined based on the X-ray diffraction analysis. The cytotoxicity of compounds 110, antifungal and anti-HIV activities of compounds 15 and the in vitro assay for glucose consumption of compounds 13 were done in the anti-diabetic model, whereas none showed obvious activity. Full article
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Open AccessArticle Search for Hydrophilic Marine Fungal Metabolites: A Rational Approach for Their Production and Extraction in a Bioactivity Screening Context
Mar. Drugs 2011, 9(1), 82-97; doi:10.3390/md9010082
Received: 18 December 2010 / Revised: 30 December 2010 / Accepted: 5 January 2011 / Published: 10 January 2011
Cited by 4 | PDF Full-text (323 KB) | HTML Full-text | XML Full-text
Abstract
In the search for bioactive natural products, our lab screens hydrophobic extracts from marine fungal strains. While hydrophilic active substances were recently identified from marine macro-organisms, there was a lack of reported metabolites in the marine fungi area. As such, we decided to
[...] Read more.
In the search for bioactive natural products, our lab screens hydrophobic extracts from marine fungal strains. While hydrophilic active substances were recently identified from marine macro-organisms, there was a lack of reported metabolites in the marine fungi area. As such, we decided to develop a general procedure for screening of hydrophobic metabolites. The aim of this study was to compare different processes of fermentation and extraction, using six representative marine fungal strains, in order to define the optimized method for production. The parameters studied were (a) which polar solvent to select, (b) which fermentation method to choose between solid and liquid cultures, (c) which raw material, the mycelium or its medium, to extract and (d) which extraction process to apply. The biochemical analysis and biological evaluations of obtained extracts led to the conclusion that the culture of marine fungi by agar surface fermentation followed by the separate extraction of the mycelium and its medium by a cryo-crushing and an enzymatic digestion with agarase, respectively, was the best procedure when screening for hydrophilic bioactive metabolites. During this development, several bioactivities were detected, confirming the potential of hydrophilic crude extracts in the search for bioactive natural products. Full article
Open AccessArticle Verrucisidinol and Verrucosidinol Acetate, Two Pyrone-Type Polyketides Isolated from a Marine Derived Fungus, Penicillium aurantiogriseum
Mar. Drugs 2010, 8(11), 2744-2754; doi:10.3390/md8112744
Received: 1 October 2010 / Revised: 22 October 2010 / Accepted: 26 October 2010 / Published: 1 November 2010
Cited by 16 | PDF Full-text (216 KB) | HTML Full-text | XML Full-text
Abstract
The new secondary metabolites verrucosidinol (1) and its derivative verrucosidinol acetate (2), together with a potent neurotoxin verrucosidin (3), a congener norverrucosidin (4) and a mixture of two known phytotoxic metabolites terrestric acids (5
[...] Read more.
The new secondary metabolites verrucosidinol (1) and its derivative verrucosidinol acetate (2), together with a potent neurotoxin verrucosidin (3), a congener norverrucosidin (4) and a mixture of two known phytotoxic metabolites terrestric acids (5 and 6), were isolated from the marine derived fungus Penicillium aurantiogriseum. Verrucosidinol has a ring-opened ethylene oxide moiety in the polyene α-pyrone skeleton, and verrucosidinol acetate is its acetate derivative. The chemical structures were determined by comparing with literature data and a combination of spectroscopic techniques, including high resolution mass spectrum and two-dimentional nuclear magnetic resonance spectroscopic analysis. Full article
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Review

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Open AccessReview Alternative and Efficient Extraction Methods for Marine-Derived Compounds
Mar. Drugs 2015, 13(5), 3182-3230; doi:10.3390/md13053182
Received: 20 April 2015 / Revised: 1 May 2015 / Accepted: 6 May 2015 / Published: 21 May 2015
Cited by 8 | PDF Full-text (424 KB) | HTML Full-text | XML Full-text
Abstract
Marine ecosystems cover more than 70% of the globe’s surface. These habitats are occupied by a great diversity of marine organisms that produce highly structural diverse metabolites as a defense mechanism. In the last decades, these metabolites have been extracted and isolated in
[...] Read more.
Marine ecosystems cover more than 70% of the globe’s surface. These habitats are occupied by a great diversity of marine organisms that produce highly structural diverse metabolites as a defense mechanism. In the last decades, these metabolites have been extracted and isolated in order to test them in different bioassays and assess their potential to fight human diseases. Since traditional extraction techniques are both solvent- and time-consuming, this review emphasizes alternative extraction techniques, such as supercritical fluid extraction, pressurized solvent extraction, microwave-assisted extraction, ultrasound-assisted extraction, pulsed electric field-assisted extraction, enzyme-assisted extraction, and extraction with switchable solvents and ionic liquids, applied in the search for marine compounds. Only studies published in the 21st century are considered. Full article
Open AccessReview Recent Advances and Applications of Experimental Technologies in Marine Natural Product Research
Mar. Drugs 2015, 13(5), 2694-2713; doi:10.3390/md13052694
Received: 12 January 2015 / Revised: 2 April 2015 / Accepted: 14 April 2015 / Published: 29 April 2015
Cited by 4 | PDF Full-text (994 KB) | HTML Full-text | XML Full-text
Abstract
Marine natural products are a rich source of novel and biologically active compounds. The number of identified marine natural compounds has grown 20% over the last five years from 2009 to 2013. Several challenges, including sample collection and structure elucidation, have limited the
[...] Read more.
Marine natural products are a rich source of novel and biologically active compounds. The number of identified marine natural compounds has grown 20% over the last five years from 2009 to 2013. Several challenges, including sample collection and structure elucidation, have limited the development of this research field. Nonetheless, new approaches, such as sampling strategies for organisms from extreme ocean environments, nanoscale NMR and computational chemistry for structural determination, are now available to overcome the barriers. In this review, we highlight the experimental technology innovations in the field of marine natural products, which in our view will lead to the development of many new drugs in the future. Full article
Open AccessReview Bioactive Dehydrotyrosyl and Dehydrodopyl Compounds of Marine Origin
Mar. Drugs 2010, 8(12), 2906-2935; doi:10.3390/md8122906
Received: 19 October 2010 / Revised: 26 November 2010 / Accepted: 1 December 2010 / Published: 6 December 2010
Cited by 17 | PDF Full-text (1926 KB) | HTML Full-text | XML Full-text
Abstract
The amino acid, tyrosine, and its hydroxylated product, 3,4-dihydroxyphenylalanine (dopa), plays an important role in the biogenesis of a number of potentially important bioactive molecules in marine organisms. Interestingly, several of these tyrosyl and dopa‑containing compounds possess dehydro groups in their side chains.
[...] Read more.
The amino acid, tyrosine, and its hydroxylated product, 3,4-dihydroxyphenylalanine (dopa), plays an important role in the biogenesis of a number of potentially important bioactive molecules in marine organisms. Interestingly, several of these tyrosyl and dopa‑containing compounds possess dehydro groups in their side chains. Examples span the range from simple dehydrotyrosine and dehydrodopamines to complex metabolic products, including peptides and polycyclic alkaloids. Based on structural information, these compounds can be subdivided into five categories: (a) Simple dehydrotyrosine and dehydrotyramine containing molecules; (b) simple dehydrodopa derivatives; (c) peptidyl dehydrotyrosine and dehydrodopa derivatives; (d) multiple dehydrodopa containing compounds; and (e) polycyclic condensed dehydrodopa derivatives. These molecules possess a wide range of biological activities that include (but are not limited to) antitumor activity, antibiotic activity, cytotoxicity, antioxidant activity, multidrug resistance reversal, cell division inhibition, immunomodulatory activity, HIV-integrase inhibition, anti-viral, and anti-feeding (or feeding deterrent) activity. This review summarizes the structure, distribution, possible biosynthetic origin, and biological activity, of the five categories of dehydrotyrosine and dehydrodopa containing compounds. Full article

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