Two new diketopiperazines from the marine sponge Dysidea sp.

A chemical investigation on the marine sponge Dysidea sp. resulted in the isolation of a series of diketopiperazines, including two new compounds, dysidines A (1) and B (2) as well as six known ones (3-8). Their structures with absolute configurations were determined on the basis of UV, IR, HRMS, NMR and calculated ECD method. Additionally, the cytotoxic, anti-inflammatory, antibacterial and antiviral activities of 1-8 were also tested. However, none of them exhibited significant bioactivities.

(+)- and (-)-Tedanine, a pair of new enantiomeric indolone alkaloids from the marine sponge Tedania sp.

(+)- and (-)-Tedanine [(+)-1 and (-)-1], a pair of new enantiomeric indolone alkaloids, along with nine compounds (2-10) were isolated from the marine sponge Tedania sp. The structures of (+)-1 and (-)-1 including absolute configurations were determined by spectroscopic analysis and quantum chemical calculation. Compounds (+)-1 and (-)-1 were the first examples of indolone alkaloids isolated from this genus. In addition, the cytotoxic and antibacterial activities of these compounds were also evaluated.

Unraveling and characterization of novel T3SS effectors in Edwardsiella piscicida.

Type III secretion system (T3SS) facilitates survival and replication of Edwardsiella piscicida in vivo. Identifying novel T3SS effectors and elucidating their functions are critical in understanding the pathogenesis of E. piscicida. E. piscicida T3SS effector EseG and EseJ was highly secreted when T3SS gatekeeper-containing protein complex EsaB-EsaL-EsaM was disrupted by EsaB deficiency. Based on this observation, concentrated secretomes of ΔesaB strain and ΔesaBΔesaN strain were purified by loading them into SDS-PAGE gel for a short electrophoresis to remove impurities prior to the in-the gel digestion and mass spectrometry. Four reported T3SS effectors and two novel T3SS effector candidates EseQ (ETAE_2009) and Trx2 (ETAE_0559) were unraveled by quantitative comparison of the identified peptides. EseQ and Trx2 were revealed to be secreted and translocated in a T3SS-dependent manner through CyaA-based translocation assay and immunofluorescent staining, demonstrating that EseQ and Trx2 are the novel T3SS effectors of E. piscicida. Trx2 was found to suppress macrophage apoptosis as revealed by TUNEL staining and cleaved caspase-3 of infected J774A.1 monolayers. Moreover, Trx2 has been shown to inhibit the p65 phosphorylation and p65 translocation into the nucleus, thus blocking the NF-κB pathway. Furthermore, depletion of Trx2 slightly but significantly attenuates E. piscicida virulence in a fish infection model. Taken together, an efficient method was established in unraveling T3SS effectors in E. piscicida, and Trx2, one of the novel T3SS effectors identified in this study, was demonstrated to suppress apoptosis and block NF- κB pathway during E. piscicida infection. IMPORTANCE Edwardsiella piscicida is an intracellular bacterial pathogen that causes intestinal inflammation and hemorrhagic sepsis in fish and human. Virulence depends on the Edwardsiella type III secretion system (T3SS). Identifying the bacterial effector proteins secreted by T3SS and defining their role is key to understanding Edwardsiella pathogenesis. EsaB depletion disrupts the T3SS gatekeeper-containing protein complex, resulting in increased secretion of T3SS effectors EseG and EseJ. EseQ and Trx2 were shown to be the novel T3SS effectors of E. piscicida by a secretome comparison between ∆esaB strain and ∆esaB∆esaN strain (T3SS mutant), together with CyaA-based translocation assay. In addition, Trx2 has been shown to suppress macrophage apoptosis and block the NF-κB pathway. Together, this work expands the known repertoire of T3SS effectors and sheds light on the pathogenic mechanism of E. piscicida.

Two New Pairs of Enantiomeric Butenolides from the Marine Sponge Suberties sp.

Two new pairs of enantiomeric butenolides, (+)- and (-)-suberiteslide A, (+)- and (-)-subertieslide B had been obtained from the marine sponge Suberties sp. The structures with absolute configurations of these compounds were unequivocally determined by spectroscopic analyses and ECD (Electronic Circular Dichroism) method. It was the first separation of butenolides from the marine sponges of genus Suberites. Additionally, the anti-inflammatory, antibacterial and cytotoxic activities of these compounds were evaluated. The result indicated that only (-)-subertieslide B showed weak anti-inflammatory activity with the IC50 value of 40.8 µM.

Spongimides A and B, two new alkaloids from the marine sponge Spongia sp.

Two new alkaloids, spongimides A (1) and B (2), along with five known ones (3-7), were isolated from the marine sponge Spongia sp. The structures of 1 and 2 were determined by the spectroscopic methods (UV, IR, MS, and NMR) and X-ray diffraction analysis. Compounds 1, 3, and 4 were the first examples of 2,4-imidazolidinediones isolated from this genus. In addition, the cytotoxic and antibacterial activities of compounds 1 and 2 were also evaluated.

A new chlorobenzoate derivative from the red alga Solieria sp.

A new chlorobenzoate derivative, solieriate (1), together with six known compounds (2-7), were isolated from the red alga Solieria sp. The structures of 1-7 were determined by comprehensive spectroscopic methods and X-ray diffraction analysis. Compound 1 is the first example of halogenated derivative isolated from this genus. In addition, 1 exhibited moderate antibacterial activity on A. baumannii with MIC value of 64 µg/ml.

A new amide from the marine sponge Haliclona baeri.

A new amide, baeriamide (1), along with nine known diketopiperazines (2-10), was isolated from the marine sponge Haliclona baeri. Their structures were identified by the means of UV, IR, MS and NMR. The absolute configuration of 1 was established by Marfey's method and comparing the specific optical rotation with the known compound HCO-Val-Gly methyl ester. Compound 1 was derived from dehydration of formylated L-valine with γ-amino-butanoic acid methyl ester. Compounds 2-10 were isolated from the genus of Haliclona for the first time. The absolute confirmation of 7 was confirmed first by the means of single-crystal X-ray diffraction. The cytotoxic, antibacterial, antiviral and antifouling activities of these compounds were also tested. However, none of them exhibited significant bioactivities.

Two new halogenated metabolites from the red alga Laurencia sp.

Two new halogenated metabolites, laurenhalogens A (1) and B (2), along with four known ones (3-6), were isolated from the red alga Laurencia sp. The structures of 1 and 2 were determined by the means of UV, IR, MS, NMR and X-ray diffraction analysis. In addition, the antibacterial activities of 1-6 were also evaluated.

Identification and Characterization of EvpQ, a Novel T6SS Effector Encoded on a Mobile Genetic Element in Edwardsiella piscicida.

In this study, a hypothetical protein (ORF02740) secreted by Edwardsiella piscicida was identified. We renamed the ORF02740 protein as EvpQ, which is encoded by a mobile genetic element (MGE) in E. piscicida genome. The evpQ gene is spaced by 513 genes from type VI secretion system (T6SS) gene cluster. Low GC content, three tRNA, and three transposase genes nearby evpQ define this MGE that evpQ localizes as a genomic island. Sequence analysis reveals that EvpQ shares a conserved domain of C70 family cysteine protease and shares 23.91% identity with T3SS effector AvrRpt2 of phytopathogenic Erwinia amylovora. Instead, EvpQ of E. piscicida is proved to be secreted at a T6SS-dependent manner, and it can be translocated into host cells. EvpQ is thereof a novel T6SS effector. Significantly decreased competitive index of ΔevpQ strain in blue gourami fish (0.53 ± 0.27 in head kidney and 0.44 ± 0.19 in spleen) indicates that EvpQ contributes to the pathogenesis of E. piscicida. At 8-, 18-, and 24-h post-subculture into DMEM, the transcription of evpQ was found to be negatively regulated by Fur and positively regulated by EsrC, and the steady-state protein levels of EvpQ are negatively controlled by RpoS. Our study lays a foundation for further understanding the pathogenic role of T6SS in edwardsiellosis.

(+)- and (-)-Spongiterpene, a pair of new valerenane sesquiterpene enantiomers from the marine sponge Spongia Sp.

(+)- and (-)-Spongiterpene [(+)-1 and (-)-1], a pair of new valerenane sesquiterpene enantiomers, along with four known compounds (2-5) were isolated from the marine sponge Spongia sp. The structures of (+)-1 and (-)-1 including absolute configurations were determined by spectroscopic analysis, quantum chemical calculation and X-ray diffraction. Compounds (+)-1 and (-)-1 were the first examples of valerenane sesquiterpenes isolated from the marine sponges. The cytotoxic activities of (+)-1 and (-)-1 were also evaluated.

Two new pyrrolidine alkaloids from the red alga Acanthophora spicifera.

Two new pyrrolidine alkaloids, acanthophoraines B (1) and C (2), together with five known ones (3-7) were isolated from the red alga Acanthophora spicifera. Their structures were elucidated by extensive spectroscopic methods and single-crystal X-ray diffraction analysis. The absolute configuration of 2 was established by ECD calculation. The antibacterial activities of 1-7 were also evaluated.

Solieritide A, a new polyketide from the red alga Solieria sp.

A new polyketide, solieritide A (1), along with six known ones (2-7), had been isolated from the red alga Solieria sp. The structures of these compounds were elucidated by spectroscopic analysis. The absolute configuration of 1 was determined by the method of X-ray diffraction. Compound 1 was a rare polyketide bearing benzopyrone ring fused with γ-butyrolactone. Compounds 2-7 were isolated from the red algae of genus Solieria for the first time. The antibacterial activities of 1-7 were also discussed.

Three New Butenolides from the Green Alga Caulerpa racemosa var. turbinata.

Three new butenolides, caulerpalide A and a pair of enantiomers, (+)-caulerpalide B and (-)-caulerpalide B, together with seven known compounds, have been isolated from the green alga Caulerpa racemosa var. turbinata. All these structures were determined by spectroscopic techniques. The absolute configurations of caulerpalide A, (+)-caulerpalide B and (-)-caulerpalide B were elucidated by the method of ECD calculation. This is the first separation of butenolides from the algae of genus Caulerpa. Additionally, the antibacterial activities of the nine isolated compounds were also evaluated.

Acanthophoraine A, a new pyrrolidine alkaloid from the red alga Acanthophora spicifera.

A new pyrrolidine alkaloid, acanthophoraine A (1), along with six known alkaloids (2-7), had been isolated from the red alga Acanthophora spicifera. The structures of these compounds were identified by spectroscopic analyses. The absolute configuration of 1 was established by ECD calculation. Compound 1 represents the first example of N-isobutyl pyrrolidone with an urea arm. The antimicrobial activity of 1 was also evaluated.[Figure: see text].

A new thiodiketopiperzaine from the marine sponge Tedania sp.

A new thiodiketopiperzaine, tedanizaine A (1), together with six known ones, were isolated from the marine sponge Tedania sp. Their structures were determined by spectroscopic analyses. The absolute configuration of 1 was established by ECD calculation. Compound 1 was the second example of thiodiketopiperazine bearing a thiazolidine unit. Cytotoxic activities of 1 were also evaluated.

Sinulaspirolactam A, a novel aza-spirocyclic valerenane sesquiterpenoid from soft coral Sinularia sp.

A novel valerenane sesquiterpenoid sinulaspirolactam A (1), together with five known compounds, was isolated from the soft coral Sinularia sp. Their structures were determined by spectroscopic analyses. The absolute configuration of 1 was established by ECD calculation. Compound 1 was the first example of valerenane sesquiterpenoid bearing an aza-spiro[4.5] ring moiety, the plausible biogenetic pathway of which was proposed. Cytotoxic activities of these compounds were also evaluated.

Antineoplastic activity of linear leucine homodipeptides and their potential mechanisms of action.

Galaxamide is a rare cyclic homopentapeptide composed of three leucines and two N-methyl leucines isolated from marine algae Galaxaura filamentosa. The strong antitumor activity of this compound makes it a promising candidate for tumor therapy. The synthesis of galaxamide, however, is a complex process, and it has poor water solubility. On the basis of its special chemical composition, we designed a series of linear leucine homopeptides. Among seven dipeptide derivatives, five compounds with terminal protection groups and methyl substitution of the hydrogen in the amido group showed remarkable inhibitory effects against various cancer cells. N-tertbutyl-D-leucine-N-methyl-D-leucinebenzyl (A7), the only stereomer condensed by two D-leucines, showed the highest antineoplastic activity. A7-treated cells showed cell cycle arrest and morphological changes typical of cells undergoing apoptosis. The population of Annexin-V positive/propidium iodide-negative cells also increased, indicating the induction of early apoptosis. A7 promoted the cleavage of caspase-9 and caspase-3, as well as increased intracellular Ca levels and decreased the mitochondrial membrane potential. Collectively, certain linear leucine dipeptides derived from cyclic pentapeptide are able to inhibit tumor cell proliferation through cell cycle arrest and apoptosis induction. The N-methyl group in the side chain and the D/L conformation of the amino-acid residue are critical for their activity.

Aspergchromones A and B, two new polyketides from the marine sponge-associated fungus Aspergillus sp. SCSIO XWS03F03.

Two new polyketides, aspergchromones A (1) and B (2), together with five known compounds, secalonic acid D (3), noreugenin (4), (3S)-5-hydroxymellein (5), (4S)-6-hydroxyisosclerone (6), and (-)-regiolone (7), were isolated from the ethyl acetate extract of marine sponge-derived fungus Aspergillus sp. SCSIO XWS03F03. Their structures were elucidated by means of spectroscopic techniques (1D and 2D NMR, MS, UV, and IR). The absolute configurations of the new compounds were established by ECD calculations. Compound 3 showed moderate antimicrobial activity.

A new α-pyrone from the deep-sea actinomycete Nocardiopsis dassonvillei subsp. dassonvillei DSM 43111(T).

A new α-pyrone, nocapyrone S (1), together with five known compounds (2-6), were isolated from the deep-sea actinomycete Nocardiopsis dassonvillei subsp. dassonvillei DSM 43111(T). Their structures were determined by spectroscopic analyses. The absolute configuration of 1 was established by quantum approaches. Cytotoxic activity of 1 was evaluated against K562, MCF-7, SGC7901, A375, Hela, and HepG2 cell lines.

Oryzamides A-E, Cyclodepsipeptides from the Sponge-Derived Fungus Nigrospora oryzae PF18.

Three new cyclohexadepsipeptides, oryzamides A-C (1-3), two isolation artifacts, oryzamides D (4) and E (5), and the known congener scopularide A (6), all possessing a rare 3-hydroxy-4-methyldecanoic acid (HMDA) substructure, were isolated from the mycelial extract of the sponge-derived fungus Nigrospora oryzae PF18. Their planar structures were elucidated by spectroscopic analysis and comparison with the literature data. The absolute configurations were determined using the advanced Marfey's method and single-crystal X-ray diffraction analysis. Among them, oryzamides D (4) and E (5) were a pair of diastereomers at the sulfur atom of the l-methionine sulfoxide residue, which showcased the possible separation of a pair of methionine sulfoxide diastereomers. The X-ray crystal structure of scopularide A (6) was obtained for the first time, thereby establishing its relative and absolute configuration at C-4 of the HMDA residue. Oryzamides A-C (1-3) did not display cytotoxic, antibacterial, antiparasitic, and NF-κB inhibitory activities.