Special Issue "Bioactive Halogenated Metabolites of Marine Origin"

Guest Editor
Prof. Dr. Vassilios Roussis
University of Athens, School of Pharmacy, Department of Pharmacognosy and Chemistry of Natural Products, Panepistimiopolis Zografou, GR 15771, Athens, Greece
E-Mail:
Interests: marine natural products; chemotaxonomy; chemical ecology

Dear Colleagues,

Halogenated secondary metabolites, while rare in terrestrial plants, are common in marine organisms due to the abundance of chloride and bromide ions in seawater. Marine biota produce a variety of halogen containing organic compounds that have 1-30 carbon atoms. Organisms that have the ability to form halogenated compounds have been found among various species of algae, bacteria, sponges, mollusks, coelenterates and several marine worms.

Interestingly, bromine is the most commonly found halogen in marine natural products, even though its concentration in seawater is lower than that of chlorine. Of all marine organisms, algae possess the highest abundance of unique biosynthetic pathways for organohalogen production.

Seaweeds probably produce halogenated organics as part of a defense system against microorganism infections, herbivore grazing, space competitors, detrimental fouling by different kinds of epiphytes, or excess of self-generated hypochlorite and hydrogen peroxide. The chemotaxonomic value of these compounds has been seriously considered in the past but the geographic and seasonal variation in the chemical composition of algal species has reduced their importance.

A significant number of algal halogenated metabolites have exhibited an impressive array of biological properties ranging from antimicrobial to insecticidal activities.

Prof. Dr. Vassilios Roussis
Guest Editor

Submission

All papers should be submitted to marinedrugs@mdpi.org with a copy to the Guest Editor. Papers will be published continuously until the deadline and will be listed together at the special issue website. Research articles and review articles are both invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editors for announcement on this website.

Submitted papers should not have been published previously, nor be under consideration for publication elsewhere. All papers are refereed through a peer-review process. A guide for authors, sample copies and other relevant information for submitting papers are available on the Instructions for Authors page. Marine Drugs is an international peer-reviewed quarterly journal published by Molecular Diversity Preservation International.

Please visit the Instructions for Authors page before submitting a paper. Open Access Article Processing Charges are 1000 CHF per paper. English correction fees (250 CHF) will be added in certain cases (1250 CHF per paper for those papers that require extensive additional formatting and/or English corrections.). Starting 1 January 2010, Article Processing Charges are of 1400 CHF per accepted article for Marine Drugs.

• biosynthesis
• structure elucidation
• bioactivity
• chemotaxonomy
• chemical ecology

Type of Paper: Review
Title: Sponge-Derived Bioactive Halogenated Metabolites
Author: RuAngelie Edrada-Ebel
Affiliation: Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, The John Arbuthnott Building, 27 Taylor Street, Glasgow G4 0NR, Scotland; E-Mail: ruangelie.edrada-ebel@strath.ac.uk
Abstract: Marine sponges are a rich source of highly halogenated compounds. Their ecological functions in sponges presumably involve resistance to feeding by fish and fouling by barnacles, bacteria, and fungi. Despite the relatively obvious difference in concentrations of chloride, bromide and iodide ions in seawater (559 mM, 0.86 mM and 0.45 μM, respectively); there exists a marked predominance of bromine containing metabolites. Halogen containing heteroatomatic natural products is particularly common class of sponge-derived secondary metabolites. Perhaps due to their enormous reactivity towards electrophilic halogenation reactions, pyrroles, indoles, phenols, and tyrosines are commonly found to be halogenated in sponges.
Keywords: halogens; Porifera; ecology; biological activity; antifouling

Type of Paper: Review
Title: Vanadium Haloperoxidases – Versatile Enzymes with Multiple Applications
Authors: Filipe Natálio ¹, Madalena Humanes ² and and Ron Wever ³
Affiliations: ¹ Institut für Physiologische Chemie, Abteilung Angewandte Molekularbiologie, Mainz Universität, Duesbergweg 6, D-55099 Mainz, Germany; E-Mail: natalio@uni-mainz.de
² Departamento e Centro de Química e Bioquímica, Faculdade de Ciências de Lisboa, Campo Grande, 1749-016 Lisboa, Portugal
³ Van't Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Nieuwe Achtergracht 129, 1018 WS Amsterdam, Holland
Abstract: Vanadium haloperoxidases (VHPO) are enzymes that contain vanadium (VO₄^3-) in their active center. VHPO are able to catalyze halogenation and oxygen transfer reactions of a wide variety of substrates in a regio- and stereoselective way. This contribution comprises an overview from initial discovery of vanadium haloperoxidases, their phylogenetic relation with another class of enzymes (e.g., phosphatases), the proposed catalytic mechanisms for halogenation and oxygen transfer reactions, until the latest aspects concerning the possibility of modulating the reactivity of these enzymes and a complete new biomimetic approach. The intrinsic and remarkable features revealed by these enzymes put these naturally derived catalysts as primary candidates for biotechnological, biomedical and industrial applications by means of green chemistry.
Keywords: enzymes; biocatalysis; green chemistry; vanadium haloperoxidades; halogenation reactions; oxygen transfer reactions

Type of Paper: Review
Title: The Halogenated Metabolism of Brown Algae (Phaeophyta), Its Biological Importance and Its Environmental Significance—A Review
Authors: Stéphane La Barre, Philippe Potin, Catherine Leblanc and Ludovic Delage
Affiliation: Station Biologique de Roscoff, University of Paris 6 and CNRS, B.P. 74, 29682 Roscoff cedex, France; Mail: labarre@sb-roscoff.fr
Abstract: Brown algae represent a major component of littoral and sublittoral zones in temperate and subtropical ecosystems. An essential adaptive feature of this ancient phylogenetic lineage is the ability to couple oxidative reactions resulting from exposure to sunlight and air with the halogenations of various substrates, thereby addressing various biotic and abiotic stresses i.e. defense against predators and protection against reactive species generated by oxidative processes. Whereas marine organisms mainly make use of bromine to increase the biological activity of secondary metabolites, some orders of brown algae such as Laminariales have also developed a striking capability to accumulate and to use iodine in physiological adaptations to stress. We review selected aspects of the halogenated metabolism of macrophytic brown algae in the light of the most recent results which point toward novel functions for iodide accumulation in kelps and the importance of bromination in cell wall modifications and adhesion properties of brown algal propagules. The importance of halogen speciation processes ranges from microbiology to biogeochemistry through enzymology, cellular biology and ecotoxicology
Keywords: halogen speciation; brown algae; defense metabolites; haloperoxidases, biogeochemistry.

Type of Paper: Review
Title: Halogenated Indole Alkaloids from Marine Invertebrates
Authors: Patricia Mendonça Pauletti, Lucas Silva Cintra, Caio Guedes Braguine, Ademar Alves da Silva, Márcio Luíz Andrade e Silva, Wilson Roberto Cunha and Ana Helena Januário
Affiliation: Núcleo de Pesquisas em Ciências Exatas e Tecnológicas, Universidade de Franca, Av. Dr. Armando Salles de Oliveira, 201, CEP 14404-600, Franca, São Paulo, Brazil; E-Mail: anahjanuario@unifran.br (A.H.J.)
Abstract: This review reports the isolation, structure elucidation and biological activities of halogenated indole alkaloids from marine invertebrates. Meridianins and related compounds (variolins, psammopemmins and aplicyanins) as well as aplysinopsins and leptoclinidamines are focused. A compilation of the ¹³C NMR data of this selected variety of natural indole alkaloids is provided.
Keywords: marine invertebrates; halogenated indole alkaloids; structure elucidation; bioactivity; ¹³C NMR data

Type of Paper: Review
Title: Halogenated Compounds from Marine Algae
Authors: Maria Teresa Cabrita ¹, Carlos Vale ¹ and Amélia Pilar Rauter ²
Affiliations: ¹ IPIMAR, Av. de Brasília, 1449-006 Lisboa, Portugal E-Mails: cvale@ipimar.pt (C.V.); tcabrita@ipimar.pt (M.T.C.)
² Centro de Química e Bioquímica/Departamento de Química e Bioquímica da Faculdade de Ciências da Universidade de Lisboa, Ed C8, Piso 5, Campo Grande, 1749-016 Lisboa, Portugal; E-Mail: aprauter@fc.ul.pt (A. P. R.)
Abstract: Marine algae produce a cocktail of halogenated metabolites with potential commercial value. The structure exhibited by these compounds goes from acyclic entities with a linear chain to complex polycyclic molecules. Their medical and pharmaceutical application has been investigated for the past two decades, although other properties like antifouling are not to be discarded. Many compounds were discovered in the last years but the need for new drugs keeps this field open as many algae species are poorly screened. Apart from the biotechnological potential, the ecological role of marine algal halogenated metabolites has somehow been overlooked. This new research field will provide valuable and novel insight into the marine ecosystem dynamics as well as a new approach to understanding biodiversity. Furthermore, understanding interactions between halogenated compounds production by algae and the environment, including anthropogenic or global climate changes, is a challenging target for the coming years. Research has been more focused on macroalgae than on phytoplankton. However, phytoplankton is a very promising material as the bottom link of the marine food chain with very quickly adaptation to environmental changes, which undoubtedly has consequences on the secondary metabolism. This paper summarizes current knowledge and revises recent progress and presents trends on the role of marine algae as producers of halogenated compounds.
Keywords: marine algae; halogenated compounds; biotechnological applications; ecological role