Special Issue "Terpenoids of Marine Origin"

Guest Editor
Dr. RuAngelie Edrada-Ebel
Strathclyde Institute of Pharmacy and Biomedical Sciences, University of Strathclyde, The John Arbuthnott Building, 27 Taylor Street, Glasgow G4 0NR, Scotland
Website: http://spider.science.strath.ac.uk/sipbs/staff/RuAngelie_Edrada-Ebel.htm
E-Mail:
Interests: natural products; drug discovery; nmr spectroscopy; metabolomics

Dear Colleagues,

The last review published on marine-derived terpenoids was in 2006. It is about time to collate and update the work done on this group of compounds in the last decade. This special issue will focus on the chemistry of terpenoids from diverse marine sources ranging from sponges, soft corals, molluscs, and other marine invertebrates. This will also include studies done on their biosyntheses, ecological significance, and biological activity.

Dr. RuAngelie Edrada-Ebel
Guest Editor

Submission

All manuscripts should be submitted to marinedrugs@mdpi.org with a copy to the Guest Editor. 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 1400 CHF per accepted paper.

• sesquiterpenes
• diterpenes
• triterpenes
• Alcyonaria
• Porifera
• Mollusca
• ecology

Type of Paper: Review
Title: Structure, Biological Activity and Phylogenetic Relationship of Terpenoids from Marine Ciliates
Authors: Graziano Guella ¹ and Fernando Dini ²
Affiliations: ¹ Biorganic Chemistry Lab , Department of Physics, University of Trento, 38050 Povo-Trento, Italy; E-Mail: guella@science.unitn.it
² Laboratory of Protistology, Department of Biology, University of Pisa, 56126 Pisa, Italy
Abstract: Ciliates is the common name assigned to a protist taxon comprising the phylum Ciliophora which includes about 7000 described species, colonizing marine, freshwater and terrestrial habitats, where they play a "keystone" role in microbial food webs. These eukaryotic microorganisms are characterized by a nuclear dualism and covering-body cilia used for locomotion and feeding. Their unicellular nature constrains the expression of large outward differentiating potentialities, to the extent that classical taxonomists are doomed to behave as “loopers” more than “splitters” in recognizing protist biodiversity. Whatever the matter stands, it is worth mentioning that genetic distance among ciliate taxa of the same taxonomic rank, species included, is far large than that occurring among multicellular representatives. Since early 90’s we have focused our attention on the secondary metabolites of the foregoing eukaryotic microorganism, in particular the marine species comprising the family Euplotidae, whose representatives occupy the top rank among ciliates as far as the cosmopolitan and ubiquitous distribution is concerned. At that time only a scanty list of secondary metabolites had been found in the freshwater ciliated species Stentor coeruleus, Blepharisma japonicum and Tetrahymena pyriformis. We had a good luck to promptly obtain large mass cultures of the marine morphospecies Euplotes crassus, whereby highly strained acetylated sesquiterpene hemiacetals (euplotane skeleton) were isolated and fully characterized up to the absolute configuration level. Many other terpenoids with new skeleta has been later isolated from Euplotidae representatives, as the sesquiterpenoids build on the bicyclo [3.2.0] heptane ring system (raikovane) from Euplotes raikovi, or the sesquiterpenoids containing octahydro-azulene moiety (rarisetane) from Euplotes rariseta, or the diterpenoids analogues of the rarisetane (focardane) from Euplotes focardi. In contrast to the highly conservative trait of the euplotins production in the E. crassus populations, the occurrence of an inter-population variability in the secondary metabolites of these morphospecies has been observed. The isolated terpenoids seem to represent a unique whole, thus serving as a reliable taxonomic tool. In the last years, however, our attention is being mainly shifted towards the morphospecies Euplotes vannus, another member of the marine Euplotes vannus-crassus-minuta species complex. The isolation from E. vannus different strains of two intriguing compounds (vannusal A and B) with an unusual and novel C₃₀ backbone and of their putative biogenetic precursor (hemivannusal) overcomes our initial taxonomic discrimination of the species-complex members relying on the presence-absence of euplotin-like compounds. The afore-mentioned terpenoids structures, elucidated by combination of mass spectrometry and NMR measurements, will be presented as well as our proposal of the pathways leading to their biosynthesis. New results on bioactivity of euplotins metabolites will also be reported. Moreover, a genetic analysis of the above-mentioned, terpenoid-producing strains have been recently carried out, comparing sequences of different genes to establish a reliable strain characterization, whereby the basis have been thrown to define relationships between genetic and physiological traits in view of a chemotaxonomic approach.
Keywords: marine ciliates; terpenoids; phylogenetic relationships