Dysideanones A-C, unusual sesquiterpene quinones from the South China Sea sponge Dysidea avara

Generalized kekulenes and clarenes as novel families of cycloarenes: structures, stability, and spectroscopic properties

Cycloarenes constitute a captivating class of polycyclic aromatic hydrocarbons with unique structures and properties, but their synthesis represents a challenging task in organic chemistry. Kekulenes and edge-extended kekulenes as classic types of cycloarenes play an important role in the comprehension of π electron distribution, but their sparse molecular diversity considerably limits their further development and application. In this work, we propose two novel classes of cycloarenes, the generalized kekulenes and the clarenes. Using density functional theory, we carry out a comprehensive study of all possible isomers of the generalized kekulenes and clarenes with different sizes. By applying a simple Hückel model, we show that π delocalization plays a crucial role in determining the relative stability of isomers. We also discover that π-π stacking is commonly present in certain larger clarenes and provides a considerable additional stabilization effect, making the corresponding isomers the lowest-energy ones. Among all considered typical looped polyarenes, generalized kekulenes and/or clarenes are revealed to be the energetically most stable forms, suggesting that these novel cycloarenes proposed here would be viable targets for future synthetic work. The simulated 1H NMR spectra and UV-vis absorption spectra provide valuable information about the electronic and optoelectronic properties for the most stable generalized kekulene and clarene species and may support their identification in future synthesis and experimental characterization.

Arenarialins A-F, Anti-inflammatory Meroterpenoids with Rearranged Skeletons from the Marine Sponge Dysidea arenaria

Six new sesquiterpene quinone/hydroquinone meroterpenoids, arenarialins A-F (1-6), were isolated from the marine sponge Dysidea arenaria collected from the South China Sea. Their chemical structures and absolute configurations were determined by HRMS and NMR data analyses coupled with DP4+ and ECD calculations. Arenarialin A (1) features an unprecedented tetracyclic 6/6/5/6 carbon skeleton, whereas arenarialins B-D (2-4) possess two rare secomeroterpene scaffolds. Arenarialins A-F showed inhibitory activity on the production of inflammatory cytokines TNF-α and IL-6 in LPS-induced RAW264.7 macrophages with arenarialin D regulating the NF-κB/MAPK signaling pathway.

Natural sesquiterpene quinone/quinols: chemistry, biological activity, and synthesis

Covering: 2010 to 2021Sesquiterpene quinone/quinols (SQs) are characterized by a C15-sesquiterpenoid unit incorporating a C6-benzoquinone/quinol moiety. Numerous unprecedented carbon skeletons have been constructed with various connection patterns between the two parts. The potent anti-cancer, anti-inflammatory, anti-microbial, anti-viral, and fibrinolytic activities of SQs are associated with their diverse structures. The representative avarol has even entered the stage of clinical phase II research as an anti-HIV agent, and was developed as paramedic medicine against psoriasis. This review provides an overall summary of 558 new natural SQs discovered between 2010 and 2021, including seven groups and sixteen structure-type subgroups, which comprehensively recapitulates their chemical structures, spectral characteristics, source organisms, biological activities, synthesis, and biosynthesis, aiming to expand the application scope of this unique natural product resource.

Combining the best of both worlds: radical-based divergent total synthesis

A mature science, combining the art of the total synthesis of complex natural structures and the practicality of delivering highly diverged lead compounds for biological screening, is the constant aim of the organic chemistry community. Delivering natural lead compounds became easier during the last two decades, with the evolution of green chemistry and the concepts of atom economy and protecting-group-free synthesis dominating the field of total synthesis. In this new era, total synthesis is moving towards natural efficacy by utilizing both the biosynthetic knowledge of divergent synthesis and the latest developments in radical chemistry. This contemporary review highlights recent total syntheses that incorporate the best of both worlds.

Enantioselective Total Synthesis of Dysiherbols A, C, and D

Herein, we report the enantioselective total synthesis of dysiherbols A, C, and D, a unique group of 6/6/5/6/6 pentacyclic quinone/hydroquinone sesquiterpenes, featuring a photo-induced quinone-alkene [2 + 2] cycloaddition and a tandem [1,2]-anionic rearrangement/cyclopropane fragmentation as key elements. Based on our total synthesis, the originally proposed structures of dysiherbols C and D have been revised. Detailed computational studies were carried out to gain deep insight into the unprecedented [1,2]-anionic rearrangement, which revealed that the transformation, albeit a symmetry-forbidden process, proceeded through a concerted manner owing to the release of high ring-strain energy and the evolution of local aromaticity in the transition state. Taking all, the present work offers a mechanistically interesting and synthetically useful approach to accessing dysiherbols and related congeners.

Chemical and biological diversity of new natural products from marine sponges: a review (2009-2018)

Marine sponges are productive sources of bioactive secondary metabolites with over 200 new compounds isolated each year, contributing 23% of approved marine drugs so far. This review describes statistical research, structural diversity, and pharmacological activity of sponge derived new natural products from 2009 to 2018. Approximately 2762 new metabolites have been reported from 180 genera of sponges this decade, of which the main structural types are alkaloids and terpenoids, accounting for 50% of the total. More than half of new molecules showed biological activities including cytotoxic, antibacterial, antifungal, antiviral, anti-inflammatory, antioxidant, enzyme inhibition, and antimalarial activities. As summarized in this review, macrolides and peptides had higher proportions of new bioactive compounds in new compounds than other chemical classes. Every chemical class displayed cytotoxicity as the dominant activity. Alkaloids were the major contributors to antibacterial, antifungal, and antioxidant activities while steroids were primarily responsible for pest resistance activity. Alkaloids, terpenoids, and steroids displayed the most diverse biological activities. The statistic research of new compounds by published year, chemical class, sponge taxonomy, and biological activity are presented. Structural novelty and significant bioactivities of some representative compounds are highlighted. Marine sponges are rich sources of novel bioactive compounds and serve as animal hosts for microorganisms, highlighting the undisputed potential of sponges in the marine drugs research and development.

Supplementary Information

The online version contains supplementary material available at 10.1007/s42995-022-00132-3.

Bioinspired Total Synthesis of Marine Anticancer Meroterpenoids Dysideanone B and Dysiherbol A and Structure Revision of Dysiherbol A

Our recent progress on the total synthesis of marine anticancer sesquiterpene quinone/hydroquinone dysideanone B and dysiherbol A is briefly highlighted. This success relied on some key transformations. The union of the terpene and quinone/hydroquinone moieties was realized through a site and stereoselective α-position alkylation of Wieland–Miescher ketone derivative with a bulky benzyl bromide. The 6/6/6/6-tetracycle of dysideanone B was constructed using an intramolecular radical cyclization and the 6/6/5/6-fused core structure of dysiherbol A was forged by an intramolecular Heck reaction, respectively. The possible origin of ethoxy group in dysideanone B was revealed by mimicking the isolation conditions at a late stage. The structure of dysiherbol A was revised through the total synthesis of this natural product. Schmalz’s synthesis of dysiherbol A was also included.

Total Synthesis of Anti-Cancer Meroterpenoids Dysideanone B and Dysiherbol A and Structural Reassignment of Dysiherbol A

The first total synthesis of marine anti-cancer meroterpenoids dysideanone B and dysiherbol A have been accomplished in a divergent way. The synthetic route features: 1) a site and stereoselective α-position alkylation of a Wieland-Miescher ketone derivative with a bulky benzyl bromide to join the terpene and aromatic moieties together and set the stage for subsequent cyclization reactions; 2) an intramolecular radical cyclization to construct the 6/6/6/6-tetracycle of dysideanone B and an intramolecular Heck reaction to forge the 6/6/5/6-fused core structure of dysiherbol A. A late-stage introduction of the ethoxy group in dysideanone B reveals that this group might come from the solvent ethanol. The structure of dysiherbol A has been revised based on our chemical total synthesis.

The identification of alkaloids from the stems of Picrasma quassioides via computer-assisted structure elucidation and quantum chemical calculations

Four new alkaloids (1-4) and one known alkaloid were isolated from the stems of Picrasma quassioides. The structures of these isolated compounds were elucidated by spectroscopic analyses, a combination of computer-assisted structure elucidation software (ACD/Structure Elucidator) and gauge-including atomic orbital (GIAO) calculation of 1 D NMR data. All compounds were evaluated for their cytotoxic activities against hepatocellular carcinoma HepG2 and Hep3B cells. However, they did not show obvious inhibitory activities.[Figure: see text].

Dysiarenone from Marine Sponge Dysidea arenaria Attenuates ROS and Inflammation via Inhibition of 5-LOX/NF-κB/MAPKs and Upregulation of Nrf-2/OH-1 in RAW 264.7 Macrophages

Background

Marine natural products harbor a variety of pharmacological activities, and the sea species have been becoming a main source of new drug candidate. In pursuit of safer and more effective anti-inflammation drug, the anti-inflammatory activities, anti-oxygenation effects and underlying molecular mechanisms of compound dysiarenone from Dysidea arenaria were investigated via LPS-induced RAW 264.7 cell model.

Methods

Firstly, RAW 264.7 cells have been stimulated with LPS and treated with dysiarenone, and the cell viability of the LPS-treated RAW 264.7 cells was examined. One-step method, DCFH-DA fluorescence probe method was used to detect reactive oxygen species (ROS). The modulation of dysiarenone on anti-inflammation was detected by enzyme-linked immunosorbent assay by measuring the release of inflammatory cytokines (TNF-α and IL-6), and inflammatory mediators (LTB4). Further, the underlying anti-inflammatory mechanism of dysiarenone was explored by determining the expression of inducible 5-LOX, MAPKs, p-Akt, and p-NF-κB p65. Oxidative stress is tightly connected with inflammation, which was also evaluated through nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase-1 (OH-1) signaling pathway.

Results

Our study unraveled that dysiarenone between 2 and 8 µM reduces the inflammation responses via suppressing the production of inflammatory cytokines (TNF-α and IL-6) and inflammatory mediators (LTB₄). Dysiarenone down-regulated the protein levels of inducible 5-LOX via the inhibition of phosphorylation of MAPKs (including p38, ERK), Akt and NF-κB p65. Additionally, dysiarenone decreases ROS accumulation by upregulating HO-1 expression via nuclear translocation of Nrf2.

Conclusion

In conclusion, we demonstrated that dysiarenone possesses anti-inflammation and anti-oxidation activity via inhibiting 5-LOX/NF-κB/MAPK and Nrf2/HO-1 signaling pathway. Dysiarenone might be a promising lead compound for inflammatory diseases.

Computational Investigation of Multifaceted Cationic Rearrangement and Stereo- and Regioselectivity in the Formation of Dysideanone's Analogues

Mechanistic studies of regiodivergent arylations of cycloalkanols to furnish enantioenriched dysideanone's analogues are performed by employing density functional theory (DFT) calculations (B3LYP-D3(SMD)/6-311++G**//B3LYP-D3/6-31+G** level of theory). On the basis of our calculations, remote γ'-C-H arylation is preferred for unsubstituted carbinol 1, an outcome from combined factors like carbocationic stability, less steric hindrance during C-C coupling, and facile dearomatization. Meanwhile, in the presence of dimethyl substituent 1^Me, regioselective γ-arylation is favored by 3.4 kcal/mol, and both findings are in agreement with the reported experimental observations. Most importantly, we concur that the barrier associated with the formation of carbocation 6 and its substituted analogues correlates with the C-H arylation outcomes. Furthermore, the β-arylation route remains unlikely for all the reaction pathways explored in this study.

Modular Synthesis of Drimane Meroterpenoids Leveraging Decarboxylative Borylation and Suzuki Coupling

Drimane meroterpenoids have attracted an increasing amount of attention in the discovery of therapeutically important probes, while the laggard synthetic accessibility is a conspicuous challenge. A new paradigm merging decarboxylative borylation and Suzuki coupling was developed as a powerful platform. Key features include the mild conditions, good chemoselectivity, operational facility, scalability, and easy availability of the coupling partners. This practical strategy enables the expedient formal synthesis of a large number of natural products and rapid generation of analogues.

Cinerols, Nitrogenous Meroterpenoids from the Marine Sponge Dysidea cinerea

Eleven new nitrogenous meroterpenoids, cinerols A-K (1-11), were isolated from the marine sponge Dysidea cinerea collected in the South China Sea, and their structures were determined by detailed spectroscopic analysis. Cinerols A (1) and B (2) feature a rare 5H-pyrrolo[1,2a]benzimidazole moiety, while cinerols C-G (3-7) are examples of rare meroterpene benzoxazoles. The cinerols are noncytotoxic to human melanoma A375 cells at the concentration of 32 μM; however, selected cinerols exhibit moderate inhibitory activity against one or more of protein-tyrosine phosphatase 1B, ATP-citrate lyase, and SH2 domain-containing phosphatase-1 with IC₅₀ values of 2.8-27 μM.

Quassinoids from Picrasma quassioides and Their Neuroprotective Effects

Quassinoids are a class of highly oxygenated degraded triterpenoids exclusively discovered from plants of the Simaroubaceae family. In this study, eight new (1-8) and 15 known quassinoids (9-23) were isolated from an extract of the stems of Picrasma quassioides. The structures were elucidated by spectroscopic analysis and electronic circular dichroism spectra combined with quantum chemical calculations. Compounds 4 and 5 represent the first examples of 18-nor-quassinoids from P. quassioides. All isolates were screened for their neuroprotective activities toward H₂O₂-induced cell damage in SH-SY5Y cells. Further study revealed that the potential protective activities of these compounds appeared to occur via the suppression of cell apoptosis and downregulation of caspase-3 activation.

Nature-inspired development of unnatural meroterpenoids as the non-toxic anti-colon cancer agents

Structural analogues of anti-cancer natural product, dysideanone, were synthesized starting from Wieland-Miescher ketone derivative. In vitro studies have been conducted to evaluate the anti-cancer potential of these unnatural meroterpenoids against colon cancer. Synthesized carbotetracycles were found to be more active as compared to their acyclic carbinol-derivatives. Unnatural carbotetracycles 4b-e, 4h, 4i and 12 were found to be highly effective against the human colon adenocarcinoma cells with IC₅₀ concentrations of 7.5-20 μM. In this series, the carbotetracyclic catechol 4e (IC₅₀ = 7.5 μM) and quinone 12 (IC₅₀ = 8 μM) were found to be the most potent compounds having the IC₅₀ of less than 10 μM with no cytotoxic effect on the normal cells. Downregulation of Cox-2 and survivin and cell cycle arrest eventually leading to apoptosis were found to be the underlying mechanism of the anti-cancer effect of these unnatural meroterpenoids.

Bioactive Prenyl- and Terpenyl-Quinones/Hydroquinones of Marine Origin †

The sea is a rich source of biological active compounds, among which terpenyl-quinones/hydroquinones constitute a family of secondary metabolites with diverse pharmacological properties. The chemical diversity and bioactivity of those isolated from marine organisms in the last 10 years are summarized in this review. Aspects related to synthetic approaches towards the preparation of improved bioactive analogues from inactive terpenoids are also outlined.

Dysiarenone, a Dimeric C21 Meroterpenoid with Inhibition of COX-2 Expression from the Marine Sponge Dysidea arenaria

Dysiarenone (1), a dimeric C₂₁ meroterpenoid featuring an unprecedented 2-oxaspiro[bicyclo[3.3.1]nonane-9,1'-cyclopentane] carbon skeleton, was isolated from the marine sponge Dysidea arenaria. The structure of 1 was determined by HRMS and NMR spectroscopic analyses coupled with ECD calculations. Dysiarenone showed inhibitory activities against COX-2 expression and the production of prostaglandin E₂ with an IC₅₀ value of 6.4 μM in LPS-stimulated RAW264.7 macrophages.

Two sesquiterpene aminoquinones protect against oxidative injury in HaCaT keratinocytes via activation of AMPKα/ERK-Nrf2/ARE/HO-1 signaling

AIMS

To investigate the cytoprotective effects of two sesquiterpene aminoquinones isolated from the marine sponge Dysidea fragilis, Dysidaminone H (DA8) and 3'-methylamino-avarone (DA14), we examined their effects against hydrogen peroxide (H₂O₂)-induced oxidative injury in human keratinocyte cell line and elucidated the underlying mechanisms.

MAIN METHODS

Cell viability was detected using a CCK-8 assay kit. Intracellular reactive oxygen species (ROS) production was measured by fluorescence of 2, 7-Dichlorodi-hydrofluorescein diacetate (DCFH-DA). Messenger RNA and protein expression were measured by real-time quantitative PCR and western blotting analysis. Immunocytochemistry was performed to determine the intracellular location of nuclear factorerythroid 2 p45 related factor 2 (Nrf2). The antioxidant response element (ARE)-luciferase reporter gene assay and RNA interference were used to establish the role of ARE and Nrf2.

KEY FINDINGS

DA8 and DA14 (DAs) resisted H₂O₂induced decline of cell viability by inhibiting the accumulation of ROS. Meanwhile, DAs increased HO-1 expression and ARE activity and induced Nrf2 expression, as well as the accumulation of Nrf2 in the cell nucleus. However, silencing of Nrf2 abolished DAs-induced HO-1 expression and ARE luciferase activation. In addition, DAs induced the phosphorylation of both cyclic AMP-activated protein kinase-α (AMPKα) and extracellular signal-regulated kinase (ERK), while specific inhibitors of AMPKα and ERK abrogated HO1 upregulation and Nrf2 activation.

SIGNIFICANCE

DAs provided cytoprotective effects against H₂O₂-induced cytotoxicity by activation of the Nrf2/ARE/HO-1 pathway via phosphorylation of AMPKα and ERK. The findings suggested that DA8 and DA14 might be the candidate therapeutic agents for skin diseases caused by oxidative injury.

Dysifragilone A inhibits LPS‑induced RAW264.7 macrophage activation by blocking the p38 MAPK signaling pathway

Dysifragilone A, a sesquiterpene aminoquinone based on a rearranged avarone skeleton, has been previously isolated and identified from the South China Sea sponge Dysidea fragilis. In the present study, anti‑inflammatory activity and the underlying molecular mechanism of dysifragilone A were studied using the classical inflammation model of lipopolysaccharide (LPS)‑activated RAW264.7 macrophage cells and an MTT assay, Griess method, ELISA and western blotting were used. The results revealed that dysifragilone A significantly reduced the release of inflammatory mediators and inflammatory cytokines in activated RAW264.7 cells, including nitric oxide (NO), prostaglandin E2,(PGE2) and interleukin‑6 (IL‑6). The protein expression levels of inducible nitric oxide synthase (iNOS), cyclooxygenase‑2 (COX‑2), and the enzymatic activity of iNOS and COX‑2 were also inhibited by dysifragilone A in a dose dependent manner. Further mechanistic investigations suggested that the anti‑inflammatory activity of dysifragilone A results from the suppression of p38 mitogen‑activated protein kinase (MAPK) activation in LPS‑activated macrophages; however, this was not associated with inhibition of the extracellular signal‑regulated kinase (ERK) or c‑Jun N‑terminal kinase (JNK) signaling pathways. Therefore, dysifragilone A and similar compounds may be anti‑inflammatories that have potential to be used in the clinic.

Regiodivergent Remote Arylation of Cycloalkanols to Dysideanone's Fused Carbotetracycles and Its Bridged Isomers

Regiodivergent γ and γ' arylations across an all-carbon quaternary center of cycloalkanols to access enantioenriched fused and bridged carbotetracycles are reported. The conformation of the carbocation guided either sequential stereospecific β-C-Me/γ-C-H-shifts or β-C-Me/γ'-C-H-shifts, providing fused carbotetracyclic analogs of dysideanone or bridged tetracycles, respectively. The reaction is highly stereoselective in building three contiguous stereocenters, where one, two, or three could be all-carbon quaternary centers. Interestingly, mechanistic studies revealed a crucial role of a methyl substituent in controlling regioselectivity.

Meroterpenoids from a Medicinal Fungus Antrodia cinnamomea

Antrodia cinnamomea, a medicinal fungus indigenous to Taiwan, has been shown to exhibit a broad spectrum of bioactivities for the treatments of alcoholic intoxication, diarrhea, abdominal pain, and fatigue, and a number of active principles have been identified. Among the bioactive entities, clinical trials of antroquinonol and 4-acetyl antroquinonol B are being carried out for curing cancer, hypercholesterolemia, and hyperlipidemia. The total synthesis of antroquinonol has been achieved; however, investigating the structure-activity relationship of this class of compounds remained difficult due to the lack of available analogues. Twenty antroquinonols isolated from A. cinnamomea IFS006 are reported herein. Their structures were elucidated using spectral analysis and by comparison with literature values. Of these, 11 antroquinonol analogues, namely, antroquinonols N-X (1-11), were previously unreported. The growth inhibitory activity of all the antroquinonol analogues was evaluated against human A549 and PC-3 cancer cell lines, and antroquinonol A exhibited the most potent activity, with GI₅₀ values of 5.7 ± 0.2 and 13.5 ± 0.2 μM, respectively. Antroquinonols V (9) and W (10) also showed growth inhibitory activity against A549 cells with GI₅₀ values of 8.2 ± 0.8 and 7.1 ± 2.1 μM, respectively, compared to 5-fluorouracil (GI₅₀ = 4.2 ± 0.2 μM).

Sesquiterpene Quinones/Hydroquinones from the Marine Sponge Spongia pertusa Esper

Nine new sesquiterpene quinones/hydroquinones (1-7, 10, and 12), three solvent-generated artifacts (8, 9, and 11), and three known compounds, 5-epi-smenospongine (13), smenospongine (14), and smenospongiadine (15), were isolated from the marine sponge Spongia pertusa Esper. The planar structures of the new compounds were elucidated on the basis of spectroscopic analyses. Their absolute configurations were determined by comparison between the calculated and experimental ECD spectra. In the cytotoxicity bioassay, compounds 13-15 exhibited activities against the human cancer cell lines U937, HeLa, and HepG2, with most potent cytotoxicities to U937 cells with IC₅₀ values of 2.8, 1.5, and 0.6 μM, respectively. In addition, compound 6 displayed CDK-2 affinity with a K_d value of 4.8 μM in a surface plasmon resonance assay.

Two highly acetylated sterols from the marine sponge Dysidea sp

Two new highly acetylated steroids, named dysiroid A (1) and dysiroid B (2), together with a known compound (3) were isolated from the marine sponges Dysidea sp. The chemical structures of 1 and 2 were elucidated by spectroscopic analyses including 1D and 2D NMR experiments and high-resolution electrospray impact mass spectroscopy. Their in vitro antimicrobial activities against a panel of bacterial strains were evaluated. Compounds 1 and 2 showed potent activity against some of the strains with minimum inhibitory concentrations ranging from 4 to 8 μg mL−1.

Antibacterial Meroterpenoids from the South China Sea Sponge Dysidea sp

Chemical investigation of the sponge Dysidea sp. afforded three new sesquiterpene phenols (1-3) and one new sesquiterpene aminoquinone (4), together with four known sesquiterpene derivatives (5-8). The structures of all compounds were unambiguously elucidated by extensive spectroscopic analysis, as well as by comparison with the literature. The absolute configurations of compounds 1-4 were determined by electron capture detector (ECD) calculations and circular dichroism (CD) spectrum analysis. Their antibacterial activity against Escherichia coli (25922), Bacillus subtilis (6633), and Staphylococcus aureus (25923) were evaluated. Compounds 1 and 3 showed weak antibacterial activity against the above three strains, whereas compounds 4-8 showed potent antibacterial activities with minimum inhibitory concentration (MIC) values in the range of 3.125 to 12.5 µg/mL.

Dysiherbols A-C and Dysideanone E, Cytotoxic and NF-κB Inhibitory Tetracyclic Meroterpenes from a Dysidea sp. Marine Sponge

Four new tetracyclic meroterpnes, dysiherbols A-C (1-3) and dysideanone E (4), were isolated from a Dysidea sp. marine sponge collected from the South China Sea. Their complete structures and absolute configurations were unambiguously determined by a combination of NMR spectroscopic data, ECD calculations, and single-crystal X-ray diffraction analysis. Within the sesquiterpene quinol structures, dysiherbols A-C possess an intriguing 6/6/5/6-fused tetracyclic carbon skeleton. The NF-κB inhibitory and cytotoxic activity evaluation disclosed that dysiherbol A (1) showed potent activity with respective IC50 values of 0.49 and 0.58 μM, which were about 10-fold and 20-fold more potent than those of dysiherbols B (2) and C (3), which feature hydroxy and ketone carbonyl groups at the C-3 position.

Marine natural products

This review covers the literature published in 2014 for marine natural products (MNPs), with 1116 citations (753 for the period January to December 2014) referring to compounds isolated from marine microorganisms and phytoplankton, green, brown and red algae, sponges, cnidarians, bryozoans, molluscs, tunicates, echinoderms, mangroves and other intertidal plants and microorganisms. The emphasis is on new compounds (1378 in 456 papers for 2014), together with the relevant biological activities, source organisms and country of origin. Reviews, biosynthetic studies, first syntheses, and syntheses that lead to the revision of structures or stereochemistries, have been included.

Asteltoxins with Antiviral Activities from the Marine Sponge-Derived Fungus Aspergillus sp. SCSIO XWS02F40

Two new asteltoxins named asteltoxin E (2) and F (3), and a new chromone (4), together with four known compounds were isolated from a marine sponge–derived fungus, Aspergillus sp. SCSIO XWS02F40. The structures of the compounds (1–7) were determined by the extensive 1D- and 2D-NMR spectra, and HRESIMS spectrometry. All the compounds were tested for their antiviral (H1N1 and H3N2) activity. Compounds 2 and 3 showed significant activity against H3N2 with the prominent IC₅₀ values of 6.2 ± 0.08 and 8.9 ± 0.3 μM, respectively. In addition, compound 2 also exhibited inhibitory activity against H1N1 with an IC₅₀ value of 3.5 ± 1.3 μM.

Meroterpenoids from a Tropical Dysidea sp. Sponge

Six new meroterpenoids (1-6), along with arenarol (7), a known rearranged drimane sesquiterpene hydroquinone, were isolated from a Dysidea sp. sponge collected from the Federated States of Micronesia. On the basis of the results of combined spectroscopic analysis, compound 1 was determined to be the cyclic ether derivative of 7, whereas 2 and 3 were assigned as the corresponding sesquiterpene quinones containing taurine-derived substituents. Compounds 4-6 possess a novel tetracyclic skeleton formed by a direct linkage between the quinone and sesquiterpene moieties. The configurations of these new compounds were assigned on the basis of combined NOESY and ECD analysis. These compounds exhibited cytotoxic and antimicrobial activities and weak inhibition against Na(+)/K(+)-ATPase.

Cytotoxic Bryostatin Derivatives from the South China Sea Bryozoan Bugula neritina

Four new macrocyclic lactones, bryostatin 21 (1) and 9-O-methylbryostatins 4, 16, and 17 (2-4), together with three known related compounds, bryostatins 4, 16, and 17 (5-7), have been isolated from an extract of the South China Sea bryozoan Bugula neritina. The structures of all compounds were unambiguously elucidated using detailed spectroscopic analysis. Structurally, the presence of a single methyl group at C-18 in compound 1 has not been observed before for known bryostatins. The isolated macrolides exhibited inhibitory effects against a small panel of human cancer cell lines.

Polybrominated diphenyl ethers with potent and broad spectrum antimicrobial activity from the marine sponge Dysidea

Three polybrominated diphenyl ethers, 2-(2',4'-dibromophenoxy)-3,5-dibromophenol (1) and 2-(2',4'-dibromophenoxy)-3,4,5-tribromophenol (2) were isolated from the marine sponge Dysidea granulosa; and 2-(2',4'-dibromophenoxy)-4,6-dibromophenol (3) from Dysidea spp. They exhibited potent and broad spectrum in vitro antibacterial activity, especially against methicillin resistant Staphylococcus aureus (MRSA), methicillin sensitive Staphylococcus aureus (MSSA), Escherichia coli O157:H7, and Salmonella. Minimal inhibitory concentration (MIC) was evaluated against 12 clinical and standard strains of Gram positive and negative bacteria. The observed MIC range was 0.1-4.0mg/L against all the Gram positive bacteria and 0.1-16.0mg/L against Gram negative bacteria. 2-(2',4″-Dibromophenoxy)-3,5-dibromophenol showed stronger broad spectrum antibacterial activity than other two compounds. 2-(2',4″-Dibromophenoxy)-3,5-dibromophenol and 2-(2',4'-dibromophenoxy)-4,6-dibromophenol are thermo-stable. The results suggest that 2-(2',4'-dibromophenoxy)-3,5-dibromophenol could be used as a potential lead molecule for anti-MRSA, anti-E. coli O157:H7, and anti-Salmonella for drug development.

Bioactive sesquiterpene quinols and quinones from the marine sponge Dysidea avara

Reports the isolation, structure determination, and cytotoxic and NF-κB inhibitory activities of eight sesquiterpene quinols and quinones from Dysidea avara.

Anticancer agents from marine sponges

Marine sponges are currently one of the richest sources of anticancer active compounds found in the marine ecosystems. More than 5300 different known metabolites are from sponges and their associated microorganisms. To survive in the complicated marine environment, most of the sponge species have evolved chemical means to defend against predation. Such chemical adaptation produces many biologically active secondary metabolites including anticancer agents. This review highlights novel secondary metabolites in sponges which inhibited diverse cancer species in the recent 5 years. These natural products of marine sponges are categorized based on various chemical characteristics.

Dysidinoid A, an unusual meroterpenoid with anti-MRSA activity from the South China Sea sponge Dysidea sp

An unusual meroterpenoid, dysidinoid A (1), was isolated from the South China Sea sponge Dysidea sp. Its structure was elucidated by extensive spectroscopic methods including HRESIMS and 2D NMR, and its absolute configuration was determined by single-crystal X-ray diffraction analysis. Dysidinoid A (1) is the first meroterpenoid from Nature bearing a 9,4-friedodrime skeleton and a 2,5-dionepyrrole unit. Dysidinoid A (1) showed potent antibacterial activity against two strains of pathogenic bacteria methicillin-resistant Staphylococcus aureus (MRSA) with MIC90 values of 8.0 μg/mL against both.

Cytotoxic aaptamine derivatives from the South China Sea sponge Aaptos aaptos

Nine new aaptamine derivatives (1-9), together with three known related compounds (10-12), have been isolated from the South China Sea sponge Aaptos aaptos. The structures of all compounds were unambiguously elucidated on the basis of spectroscopic analyses. Structurally, compound 1 possesses a piperidinyl group fused to a demethyl(oxy)aaptamine moiety, whereas compounds 3-6 share an imidazole-fused 1H-benzo[de][1,6]naphthyridin-2(4H)-one skeleton. The cytotoxic activities of the compounds were evaluated against various human cancer cell lines, and compounds 2, 8, 11, and 12 showed potent cytotoxicities against HL60, K562, MCF-7, KB, HepG2, and HT-29 cells, with IC50 values in the range of 0.03 to 8.5 μM.