Table of Contents

Abstract: The 1,4-benzoquinone moiety is a common structural feature in a large number of compounds that have received considerable attention owing to their broad spectrum of biological activities. The cytotoxic and antiproliferative properties of many natural sesquiterpene quinones and hydroquinones from sponges of the order Dictyoceratida, such as avarol, avarone, illimaquinone, nakijiquinone and bolinaquinone, offer promising opportunities for the development of new antitumor agents. The present review summarizes the structure and cytotoxicity of natural terpenequinones/hydroquinones and their bioactive analogues and derivatives.

Abstract: Human immunodeficiency virus (HIV) infection causes acquired immune deficiency syndrome (AIDS) and is a global public health issue. Anti-HIV therapy involving chemical drugs has improved the life quality of HIV/AIDS patients. However, emergence of HIV drug resistance, side effects and the necessity for long-term anti-HIV treatment are the main reasons for failure of anti-HIV therapy. Therefore, it is essential to isolate novel anti-HIV therapeutics from natural resources. Recently, a great deal of interest has been expressed regarding marine-derived anti-HIV agents such as phlorotannins, sulfated chitooligosaccharides, sulfated polysaccharides, lectins and bioactive peptides. This contribution presents an overview of anti-HIV therapeutics derived from marine resources and their potential application in HIV therapy.

Abstract: When 21 species of sea anemones were screened for Kv1 potassium channel toxins by competitive inhibition of the binding of ¹²⁵I-α-dendrotoxin to rat synaptosomal membranes, 11 species (two species of Actiniidae, one species of Hormathiidae, five species of Stichodactylidae and three species of Thalassianthidae) were found to be positive. Furthermore, full-length cDNAs encoding type 1 potassium channel toxins from three species of Stichodactylidae and three species of Thalassianthidae were cloned by a combination of RT-PCR, 3′RACE and 5′RACE. The precursors of these six toxins are commonly composed of signal peptide, propart and mature peptide portions. As for the mature peptide (35 amino acid residues), the six toxins share more than 90% sequence identities with one another and with κ_1.3-SHTX-She1a (Shk) from Stichodactyla helianthus but only 34–63% identities with the other type 1 potassium channel toxins.

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. 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.

Abstract: Two new eunicellin-type diterpenoids, cladielloides A (1) and B (2), which were found to possess a 2-hydroxybutyroxy group in their structures, were isolated from an Indonesian octocoral identified as Cladiella sp. The structures of eunicellins 1 and 2 were elucidated by spectroscopic methods. Cladielloide B (2) exhibited moderate cytotoxicity toward CCRF-CEM tumor cells and this compound displayed significant inhibitory effects on superoxide anion generation and elastase release by human neutrophils.

Abstract: On a global research expedition, over 500 bacterial strains inhibitory towards pathogenic bacteria were isolated. Three hundred of the antibacterial strains were assigned to the Vibrionaceae family. The purpose of the present study was to investigate the phylogeny and bioactivity of five Vibrionaceae strains with pronounced antibacterial activity. These were identified as Vibrio coralliilyticus (two strains), V. neptunius (two strains), and Photobacterium halotolerans (one strain) on the basis of housekeeping gene sequences. The two related V. coralliilyticus and V. neptunius strains were isolated from distant oceanic regions. Chemotyping by LC-UV/MS underlined genetic relationships by showing highly similar metabolite profiles for each of the two V. coralliilyticus and V. neptunius strains, respectively, but a unique profile for P. halotolerans. Bioassay-guided fractionation identified two known antibiotics as being responsible for the antibacterial activity; andrimid (from V. coralliilyticus) and holomycin (from P. halotolerans). Despite the isolation of already known antibiotics, our findings show that marine Vibrionaceae are a resource of antibacterial compounds and may have potential for future natural product discovery.

Abstract: The sponge Fascaplysinopsis sp. (order Dictyoceratida, Family Thorectidae) from the west coast of Madagascar (Indian Ocean) is a particularly rich source of bioactive nitrogenous macrolides. The previous studies on this organism led to the suggestion that the latter should originate from associated microsymbionts. In order to evaluate the influence of microsymbionts on lipid content, 10 samples of Fascaplysinopsis sp. were investigated for their sterol composition. Contrary to the secondary metabolites, the sterol patterns established were qualitatively and quantitatively stable: 14 sterols with different unsaturated nuclei, D⁵, D⁷ and D^5,7, were identified; the last ones being the main sterols of the investigated sponges. The chemotaxonomic significance of these results for the order Dictyoceratida is also discussed in the context of the literature. The conjugated diene system in D^5,7 sterols is known to be unstable and easily photo-oxidized during storage and/or experiments to produce 5a,8a-epidioxy sterols. However, in this study, no 5a,8a-epidioxysterols (or only trace amounts) were observed. Thus, it was supposed that photo-oxidation was avoided thanks to the natural antioxidants detected in Fascaplysinopsis sp. by both the DPPH and b-caroten bleaching assays.

Abstract: The antiproliferative activity of 52 volatile compounds released from bacteria was investigated in agar diffusion assays against medically important microorganisms and mouse fibroblasts. Furthermore, the activity of these compounds to interfere with the quorum-sensing-systems was tested with two different reporter strains. While some of the compounds specific to certain bacteria showed some activity in the antiproliferative assay, the compounds common to many bacteria were mostly inactive. In contrast, some of these compounds were active in the quorum-sensing-tests. γ-Lactones showed a broad reactivity, while pyrazines seem to have only low intrinsic activity. A general discussion on the ecological importance of these findings is given.

Abstract: The starfish Narcissia canariensis harvested from the coasts off Dakar, Senegal, was investigated for glycolipids (GL). This report deals with the isolation, characterization and biological activity of a fraction F13-3 separated from the GL mixture and selected according to its ability to inhibit KB cell proliferation after 72 hours of treatment. Firstly, a GL mixture F13 was obtained that accounted for 1.36% of starfish biomass (dry weight) and 0.36% of total lipids. The fraction F13-3 obtained from F13 contained three homologous GL identified as peracetylated derivatives on the basis of chemical and spectroscopic evidence. These contained a β-glucopyranoside as sugar head, a 9-methyl-branched 4,8,10-triunsaturated long-chain aminoalcohol as sphingoid base and amide-linked 2-hydroxy fatty acid chains. The majority (63%) had an amide-linked 2‑hydroxydocosanoic acid chain and was identified as the ophidiacerebroside-C, firstly isolated from the starfish Ophidiaster ophidiamus. The minor components of F13-3 differed by one more or one less methylene group, and corresponded to ophidiacerebroside-B and -D. We found that F13-3 displayed an interesting cytotoxic activity over 24 hours on various adherent human cancerous cell lines (multiple myeloma, colorectal adenocarcinoma and glioblastoma multiforme) with an IC₅₀ of around 20 μM.