Table of Contents

Abstract: Chemical investigations of the Dongsha Atoll soft coral Lobophytum durum resulted in the isolation of five new cembranolides, durumolides M–Q (1–5). The structures of compounds 1–5 were characterized by the interpretation of extensive spectroscopic analysis. Compound 4 exhibited cytotoxicity against P-388 (mouse lymphocytic leukemia) cell line with an ED₅₀ of 3.8 μg/mL. Moreover, compound 5 showed significant antiviral activity against human cytomegalovirus with an IC₅₀ of 5.2 μg/mL.

Abstract: Five new cembrane-type diterpenoids, lobocrassins A–E (1–5), were isolated from the soft coral Lobophytum crassum. The structures of cembranes 1–5 were established by spectroscopic and chemical methods and by comparison of the spectral data with those of known cembrane analogues. Lobocrassin A (1) is the first cembranoid possessing an α-chloromethyl-α-hydroxy-γ-lactone functionality and is the first chlorinated cembranoid from soft corals belonging to the genus Lobophytum. Lobocrassins B (2) and C (3) were found to be the stereoisomers of the known cembranes, 14-deoxycrassin (6) and pseudoplexaurol (7), respectively. Lobocrassin B (2) exhibited modest cytotoxicity toward K562, CCRF-CEM, Molt4, and HepG2 tumor cells and displayed significant inhibitory effects on the generation of superoxide anion and the release of elastase by human neutrophils.

Abstract: The regulation of the inflammatory response is essential to maintaining homeostasis. Several studies have investigated new drugs that may contribute to avoiding or minimizing excessive inflammatory process. The aim of this study was to evaluate the effect of extracts of green algae Caulerpa mexicana on models inflammation. In mice, the inflammatory peritonitis model is induced by zymosan. Previous treatment of mice with aqueous and methanolic extracts of C. mexicana was able to suppress the cell migration to the peritoneal cavity, in a time-dependent but not in a dose-dependent manner. The treatment of mice with C. mexicana extracts also decreased the xylene-induced ear edema, exerting strong inhibitory leukocyte migration elicited by zymosan into the air pouch. We concluded that administration of the extracts resulted in a reduction of cell migration to different sites as well as a decrease in edema formation induced by chemical irritants. This study demonstrates for the first time the anti-inflammatory effect of aqueous and methanolic extracts from the green marine algae Caulerpa mexicana.

Abstract: The ischemic disorders, in which platelet aggregation and blood coagulation are involved, represent a major cause of disability and death worldwide. The antithrombotic therapy has unsatisfactory performance and may produce side effects. So, there is a need to seek molecules with antithrombotic properties. Marine organisms produce substances with different well defined ecological functions. Moreover, some of these molecules also exhibit pharmacological properties such as antiviral, anticancer, antiophidic and anticoagulant properties. The aim of this study was to evaluate, through in vitro tests, the effect of two extracts of brown algae and ten marine sponges from Brazil on platelet aggregation and blood coagulation. Our results revealed that most of the extracts were capable of inhibiting platelet aggregation and clotting measured by plasma recalcification tests, prothrombin time, activated partial thromboplastin time, and fibrinogenolytic activity. On the other hand, five of ten species of sponges induced platelet aggregation. Thus, the marine organisms studied here may have molecules with antithrombotic properties, presenting biotechnological potential to antithrombotic therapy. Further chemical investigation should be conducted on the active species to discover useful molecules for the development of new drugs to treat clotting disorders.

Abstract: In this study, we elucidated the inhibitory effect of fucoidan from marine brown algae on the lipid accumulation in differentiated 3T3-L1 adipocytes and its mechanism. The treatment of fucoidan in a dose-dependent manner was examined on lipid inhibition in 3T3-L1 cells by using Oil Red O staining. Fucoidan showed high lipid inhibition activity at 200 µg/mL concentration (P < 0.001). Lipolytic activity in adipocytes is highly dependent on hormone sensitive lipase (HSL), which is one of the most important targets of lipolytic regulation. Here, we examined the biological response of fucoidan on the protein level of lipolysis pathway. The expressed protein levels of total hormone sensitive lipase (HSL) and its activated form, phosphorylated-HSL were significantly increased at concentration of 200 µg/mL fucoidan. Furthermore, insulin-induced 2-deoxy-D-[³H] glucose uptake was decreased up to 51% in fucoidan-treated cells as compared to control. Since increase of HSL and p-HSL expression and decrease of glucose uptake into adipocytes are known to lead to stimulation of lipolysis, our results suggest that fucoidan reduces lipid accumulation by stimulating lipolysis. Therefore, these results suggest that fucoidan can be useful for the prevention or treatment of obesity due to its stimulatory lipolysis.

Abstract: To investigate the structurally novel and bioactive natural compounds from marine-derived microorganisms under high salinity, the fungus Aspergillus terreus PT06-2 was isolated from the sediment of the Putian Sea Saltern, Fujian, China. Three new compounds, terremides A (1) and B (2) and terrelactone A (3), along with twelve known compounds (4–15) were isolated and identified from the fermentation broth of A. terreus PT06-2 at 10% salinity. Among these metabolites, compounds 4 and 15 only produced in the 10% salinity culture, were identified as methyl 3,4,5-trimethoxy-2-(2-(nicotinamido) benzamido) benzoate, and (+)-terrein, respectively. The new compounds 1 and 2 exhibited antibacterial activity against Pseudomonas aeruginosa and Enterobacter aerogenes with MIC values of 63.9 and 33.5 μM, respectively. Compounds 5 showed moderate anti-H1N1 activity and lower cytotoxicity with IC₅₀ and CC₅₀ values of and 143.1 and 976.4 μM, respectively.

Abstract: The diversity of symbiotic fungi associated with the gorgonian coral Echinogorgia rebekka from the Weizhou coral reef in the South China Sea was investigated. Combined with morphologic traits, ITS-rDNA sequences revealed 18 fungal strains from this gorgonian. All of the 18 fungi belonged to the phylum Ascomycota and were distributed among seven genera in five orders: Eurotiales (Aspergillus and Penicillium), Pleosporales (Alternaria), Capnodiales (Cladosporium), Trichosphaeriales (Nigrospora) and Hypocreales (Hypocrea and Nectria). Antibacterial activities of these fungal strains were investigated with five pathogenic bacteria. All of the 18 fungal strains displayed different levels of antibacterial activities, most of which exhibited moderate to high antibacterial activities to the Gram-positive pathogens Staphylococcus aureus and Micrococcus tetragenus, and showed relatively low bioactivities to other three pathogenic bacteria. Several fungal strains in the genera Penicillium and Cladosporium with strong antibacterial activities provide potential for further research on isolation of bioactive secondary metabolites.

Abstract: Surface-associated marine bacteria often produce secondary metabolites with antagonistic activities. In this study, tropodithietic acid (TDA) was identified to be responsible for the antibacterial activity of the marine epiphytic bacterium Pseudovibrio sp. D323 and related strains. Phenol was also produced by these bacteria but was not directly related to the antibacterial activity. TDA was shown to effectively inhibit a range of marine bacteria from various phylogenetic groups. However TDA-producers themselves were resistant and are likely to possess resistance mechanism preventing autoinhibition. We propose that TDA in isolate D323 and related eukaryote-associated bacteria plays a role in defending the host organism against unwanted microbial colonisation and, possibly, bacterial pathogens.

Abstract: Six new (3Z,5E)-11,20-epoxybriara-3,5-dien-7,18-olide diterpenoids, gemmacolides N–S (1–6), were isolated together with four known analogues, juncenolide D, and juncins R, S and U (7–10), from the South China Sea gorgonian Dichotella gemmacea. The structures of the new compounds were elucidated by the detailed analysis of spectroscopic data in combination with the comparison with reported data. The absolute configuration of 1 was determined by a TDDFT calculation of its solution ECD spectrum, affording the determination of absolute configuration of other analogues by simply comparing their ECD spectra with that of 1. The cytotoxic and antimicrobial activities of these compounds were evaluated. In preliminary in vitro bioassays, compounds 4, 5, 6, 8 and 9 showed cytotoxicity against A549 and MG63, while compounds 1, 2, 4, 7–10 showed antimicrobial activity against the fungus Septoria tritici and the bacterium Escherichia coli.

Abstract: Carotenoids of the corals Acropora japonica, A. secale, and A. hyacinthus, the tridacnid clam Tridacna squamosa, the crown-of-thorns starfish Acanthaster planci, and the small sea snail Drupella fragum were investigated. The corals and the tridacnid clam are filter feeders and are associated with symbiotic zooxanthellae. Peridinin and pyrrhoxanthin, which originated from symbiotic zooxanthellae, were found to be major carotenoids in corals and the tridacnid clam. The crown-of-thorns starfish and the sea snail D. fragum are carnivorous and mainly feed on corals. Peridinin-3-acyl esters were major carotenoids in the sea snail D. fragum. On the other hand, ketocarotenoids such as 7,8-didehydroastaxanthin and astaxanthin were major carotenoids in the crown-of-thorns starfish. Carotenoids found in these marine animals closely reflected not only their metabolism but also their food chains.

Abstract: Pseudonocardians A–C (2–4), three new diazaanthraquinone derivatives, along with a previously synthesized compound deoxynyboquinone (1), were produced by the strain SCSIO 01299, a marine actinomycete member of the genus Pseudonocardia, isolated from deep-sea sediment of the South China Sea. The structures of compounds 1–4 were determined by mass spectrometry and NMR experiments (¹H, ¹³C, HSQC, and HMBC). The structure of compound 1, which was obtained for the first time from a natural source, was confirmed by X-ray analysis. Compounds 1–3 exhibited potent cytotoxic activities against three tumor cell lines of SF-268, MCF-7 and NCI-H460 with IC₅₀ values between 0.01 and 0.21 μm, and also showed antibacterial activities on Staphylococcus aureus ATCC 29213, Enterococcus faecalis ATCC 29212 and Bacillus thuringensis SCSIO BT01, with MIC values of 1–4 μg mL⁻¹.