Zeylleucapenoids A-D, Highly Oxygenated Diterpenoids with Anti-Inflammatory Activity from Leucas zeylanica (L.) R. Br.

Four previously undescribed highly oxygenated diterpenoids (1-4), zeylleucapenoids A-D, characterized by halimane and labdane skeletons, were isolated from the aerial parts of Leucas zeylanica. Their structures were elucidated primarily via NMR experiments. The absolute configuration of 1 was established using theoretical ECD calculations and X-ray crystallographic analysis, whereas those for 2-4 were assigned using theoretical ORD calculations. Zeylleucapenoids A-D were tested for anti-inflammatory activity against nitric oxide (NO) production in RAW264.7 macrophages, of which only 4 showed significant efficacy with an IC50 value of 38.45 µM. Further, active compound 4 was also evaluated for the inhibition of the release of pro-inflammatory cytokines TNF-α and IL-6 and was found to have a dose-dependent inhibitory effect, while it showed nontoxic activity for zebrafish embryos. A subsequent Western blotting experiment revealed that 4 inhibited the expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Furthermore, molecular docking analysis indicated that the possible mechanism of action for 4 may be bind to targets via hydrogen and hydrophobic bond interactions.

Ansamycin derivatives from the marine-derived Streptomyces sp. SCSGAA 0027 and their cytotoxic and antiviral activities.

Fourteen ansamycin derivatives including seven new herbimycins G-L (1-6) and divergolide O (7), and seven known analogues were isolated from a culture broth of the marine-derived Streptomyces sp. SCSGAA 0027. Their complete structures were determined by detailed analysis of spectroscopic data and quantum chemical calculations. Compounds 1-5 and 7 featured an additional eight-membered O-heterocycle that has rarely been reported for ansamycins, and the Z,Z- and E,E-configurations for Δ2,Δ4 were reported for the first time in geldanamycin analogues. Compound 1 exhibited weak inhibition activity towards Hsp90α with an IC50 value of 96 µM, 2-5 showed mild cytotoxicity against four human cancer cell lines with IC50 values ranging from 13 µM to 86 µM, and 7 had moderate anti-HSV-1 activity with an IC50 value of 19 µM and very weak cytotoxicity towards Vero cell. The possible biosynthetic pathways for 1-5 were proposed. And their structure-bioactivity relationship was also discussed.

New dibenzodioxocinone and pyran-3,5-dione derivatives from the deep-sea-derived fungus Penicillium canescens SCSIO z053.

A new isopentylated dibenzodioxocinone, canescenin A (1), and a new isopentylated pyran-3,5-dione derivative, canescenin B (2), were isolated from an extract of the deep-sea-derived fungus Penicillium canescens SCSIO z053. Their structures were elucidated by spectroscopic analysis. It was rare to obtain pyran-3,5-dione derivatives from nature. Antibacterial, cytotoxic, and antiviral activities of 1 and 2 were also evaluated.

Bioactive Polyketide Derivatives from the Mangrove-Derived Fungus Daldinia eschscholtzii HJ004.

Five new tetralones, daldiniones A-E (1-5), three new chromones, 7-hydroxy-5-methoxy-2,3-dimethylchromone (9), 5-methoxy-2-propylchromone (10), and 7-ethyl-8-hydroxy-6-methoxy-2,3-dimethylchromone (11), and two new lactones, helicascolides D and E (16 and 17), together with nine known metabolites (6-8, 12-15, and 18-19) were isolated from the mangrove-derived fungus Daldinia eschscholtzii HJ004. The structures and absolute configurations of the new compounds were determined by analyzing MS and NMR data and utilizing GIAO based 13C NMR chemical shift calculations and quantum chemical electronic circular dichroism (ECD) calculations. Compounds 9, 13, and 18 showed inhibitory activities against α-glucosidase with IC50 values of 13, 15, and 16 µM, respectively.

Four New Insecticidal Xanthene Derivatives from the Mangrove-Derived Fungus Penicillium sp. JY246.

Four new xanthene derivatives, penicixanthenes A-D (1-4), and one known compound 5 were isolated from a marine mangrove endophytic fungus Penicillium sp. JY246 that was obtained from the stem of Ceriops tagal. Their structures were determined by detailed NMR, MS spectroscopic data, modified Mosher's method, and calculated electronic circular dichroism data. All of the isolated compounds were examined for insecticidal activity. Compounds 2 and 3 showed growth inhibition activity against newly hatched larvae of Helicoverpa armigera Hubner with the IC50 values 100 and 200 µg/mL, respectively, and compounds 1, 3, and 4 showed insecticidal activity against newly hatched larvae of Culex quinquefasciatus with LC50 values of 38.5 (±1.16), 11.6 (±0.58), and 20.5 (±1) µg/mL, respectively. The four xanthene derivatives have the potential to be developed as new biopesticides.

Bioactive Lactones from the Mangrove-Derived Fungus Penicillium sp. TGM112.

Three new lactones penicilactones A-C (1-3) were obtained from the mangrove-derived fungus Penicillium sp. TGM112. Their structures and absolute configurations were determined by detailed NMR, MS spectroscopic data, Mo2(OAc)4-induced electronic circular dichroism (ECD), and circular dichroism (CD) spectroscopy. Compound 1 showed antibacterial activity against Staphylococcus aureus with an MIC value of 6.25 µg/mL. Compound 2 showed insecticidal activity against newly hatched larvae of Culex quinquefasciatus with the LC50 value of 78.5 (±0.58) µg/mL.

Hygrocin C from marine-derived Streptomyces sp. SCSGAA 0027 inhibits biofilm formation in Bacillus amyloliquefaciens SCSGAB0082 isolated from South China Sea gorgonian.

Several ansamycins have been reported to inhibit bacterial biofilm formation and accelerate the eradication of developed biofilms, but little is known about the effect of hygrocin C, an ansamycin, on bacterial biofilm formation. Here, hygrocin C was isolated from the marine-derived Streptomyces sp. SCSGAA 0027 and reported for the first time to be capable of inhibiting the biofilm formation of Staphylococcus aureus and Bacillus amyloliquefaciens SCSGAB0082 with the production of anti-microbial lipopeptides from South China Sea gorgonian Subergorgia suberosa at concentrations of less than minimum inhibitory concentrations. Moreover, hygrocin C also promoted the eradication of developed biofilms, affected the biofilm architecture, and lowered the extracellular polymeric matrix formation, cell motility, and surface hydrophobicity in B. amyloliquefaciens, which was in accordance with the inhibition of biofilm formation. Furthermore, transcriptome analysis revealed that hygrocin C altered the transcripts of several genes associated with bacterial chemotaxis and flagellar, two-component system and the synthesis of arginine and histidine, which are important for bacterial biofilm formation. In conclusion, hygrocin C could be used as a potential biofilm inhibitor against S. aureus and B. amyloliquefaciens. But further genetic investigations are needed to provide more details for elucidation of the molecular mechanisms responsible for the effects of hygrocin C on B. amyloliquefaciens biofilm formation.

New Furanone Derivatives and Alkaloids from the Co-Culture of Marine-Derived Fungi Aspergillus sclerotiorum and Penicillium citrinum.

Six new compounds including two furanone derivatives sclerotiorumins A and B (1 and 2), one novel oxadiazin derivative sclerotiorumin C (3), one pyrrole derivative 1-(4-benzyl-1H-pyrrol-3-yl)ethanone (4), and two complexes of neoaspergillic acid aluminiumneohydroxyaspergillin (5) and ferrineohydroxyaspergillin (6) were isolated from the co-culture of marine-derived fungi Aspergillus sclerotiorum and Penicillium citrinum. Compound 3 was the first natural 1,2,4-oxadiazin-6-one. Compound 5 showed significant and selective cytotoxicity against human histiocytic lymphoma U937 cell line (IC50  = 4.2 µm) and strong toxicity towards brine shrimp (LC50  = 6.1 µm), and oppositely increased the growth and biofilm formation of Staphylococcus aureus.

Nahuoic Acids B-E, Polyhydroxy Polyketides from the Marine-Derived Streptomyces sp. SCSGAA 0027.

Four new polyol polyketides containing a decalin ring, nahuoic acids B-E (1-4), together with a known analogue, nahuoic acid A (5), possessing an unprecedented carbon skeleton, were isolated from a culture broth of the marine-derived Streptomyces sp. SCSGAA 0027. Their structures were determined by detailed analysis of spectroscopic data and chemical transformations including acetonide formation and Mosher's ester method. Compounds 1-5 showed weak antibiofilm activity against Shewanella onedensis MR-1 biofilm. This is the first series of analogues of the novel selective SETD8 inhibitor nahuoic acid A.

Antifouling potentials of eight deep-sea-derived fungi from the South China Sea.

Marine-derived microbial secondary metabolites are promising potential sources of nontoxic antifouling agents. The search for environmentally friendly and low-toxic antifouling components guided us to investigate the antifouling potentials of eight novel fungal isolates from deep-sea sediments of the South China Sea. Sixteen crude ethyl acetate extracts of the eight fungal isolates showed distinct antibacterial activity against three marine bacteria (Loktanella hongkongensis UST950701-009, Micrococcus luteus UST950701-006 and Pseudoalteromonas piscida UST010620-005), or significant antilarval activity against larval settlement of bryozoan Bugula neritina. Furthermore, the extract of Aspergillus westerdijkiae DFFSCS013 displayed strong antifouling activity in a field trial lasting 4 months. By further bioassay-guided isolation, five antifouling alkaloids including brevianamide F, circumdatin F and L, notoamide C, and 5-chlorosclerotiamide were isolated from the extract of A. westerdijkiae DFFSCS013. This is the first report about the antifouling potentials of metabolites of the deep-sea-derived fungi from the South China Sea, and the first stage towards the development of non- or low-toxic antifouling agents from deep-sea-derived fungi.

Territrem and butyrolactone derivatives from a marine-derived fungus Aspergillus terreus.

Seventeen lactones including eight territrem derivatives (1-8) and nine butyrolactone derivatives (9-17) were isolated from a marine-derived fungus Aspergillus terreus SCSGAF0162 under solid-state fermentation of rice. Compounds 1-3 and 9-10 were new, and their structures were elucidated by spectroscopic analysis. The acetylcholinesterase inhibitory activity and antiviral activity of compounds 1-17 were evaluated. Among them, compounds 1 and 2 showed strong inhibitory activity against acetylcholinesterase with IC50 values of 4.2 ± 0.6, 4.5 ± 0.6 nM, respectively. This is the first time it has been reported that 3, 6, 10, 12 had evident antiviral activity towards HSV-1 with IC50 values of 16.4 ± 0.6, 6.34 ± 0.4, 21.8 ± 0.8 and 28.9 ± 0.8 µg·mL-1, respectively. Antifouling bioassay tests showed that compounds 1, 11, 12, 15 had potent antifouling activity with EC50 values of 12.9 ± 0.5, 22.1 ± 0.8, 7.4 ± 0.6, 16.1 ± 0.6 µg·mL-1 toward barnacle Balanus amphitrite larvae, respectively.

Anti-neuroinflammatory andrastin-type meroterpenoids from the marine-derived fungus Penicillium chrysogenum HNNU w0032.

A new andrastin-type meroterpenoid penimerodione A (1), and three known analogues (2-4), were isolated from the culture of a marine-derived fungus Penicillium chrysogenum HNNU w0032 by the guidance of MS/MS-based molecular networking. The planar structure of 1 was established by extensive NMR spectroscopic and HRESIMS analyses, and the absolute configuration was elucidated by a single-crystal X-ray diffraction. Compound 1 showed significant inhibitory effect on NO production in LPS-stimulated BV-2 macrophages with an IC50 value of 5.9 ± 0.3 µM. The Western blot result revealed that compound 1 exerted an anti-neuroinflammatory effect via the MAPK signalling pathway.

Polyketides from the mangrove-derived fungus Penicillium robsamsonii HNNU0006.

Seven polyketides, including an undescribed depsidone (1) and six previously reported 3,6,8-trihydroxy-1-methylxanthone (2), 7-hydroxy-2-(2-hydroxypropyl)-5-methylchromone (3), methyl3-chloro-6-hydroxy-2-(4-hy-droxy-2-methoxy-6-methylphenoxy)-4- methoxybenzoate (4), xylarianin A (5), 4,5-dihydroxy-6-(6'-methylsalicyloxy)-2-hydro-xymethyl-2-cyclohexen-1-one (6) and alternariol (7), have been isolated from cultures of the mangrove-derived fungus Penicillium robsamsonii HNNU0006. The structure of compound 1 was elucidated by extensive spectroscopic analysis and X-ray crystallography. Furthermore, all the compounds were evaluated their cytotoxic activities, and compounds 1 and 7 showed weak cytotoxicity against two cell lines Vero and A549 with IC50 values ranging from 95.6 and 296.5 µM, relative to the positive control Etoposide phosphate with IC50 values of 24.5 and 18.7 µM, respectively.

Alkaloid-metabolites from the mangrove-derived fungus Penicillium robsamsonii HNNU0006.

Nine metabolites, including three undescribed alkaloids pyripyropenes VW (1-2), penicioxa A (4), two previously reported pyripyropene A (3), oxaline (5), three grisephenone-type xanthone derivatives (6-8), and a diphenyl ether derivative 4-chloro-7,4'-dihydroxy-5,2'-dimethoxy-2-methylformate-6'-methybenzophone (9), were isolated from cultures of the mangrove-derived fungus Penicillium robsamsonii HNNU0006. Their structures were determined by spectroscopic analysis, ECD calculations, together with DP4+ probability analysis. Furthermore, all the isolated compounds were tested for cytotoxicity and anti-phytopathogenic fungal activities. Compounds 6-8 showed moderate cytotoxicity against tumor cell lines A549, with IC50 values ranging from 5.68 ± 0.21 to 9.71 ± 0.34 µg/mL, respectively.

Drimane-type sesquiterpenoids and their anti-inflammatory evaluation from Pyrrhoderma noxium HNNU0524.

Chemical investigation of a culture broth from the marine-derived fungus Pyrrhoderma noxium HNNU0524 yielded two new compounds including a drimane-type sesquiterpenoid named pyrrnoxin A (1) and a benzoic acid derivative, pyrrnoxin B (5), together with three related known analogues (2-4). The chemical structures of 1 and 5 were determined by detailed analysis of spectroscopic data, single-crystal X-ray crystallography, quantum mechanics-based DP4+ and ECD calculations. Compounds 2 and 3 moderately inhibited NO production of lipopolysaccharide-induced microglia cells BV2 with IC50 values of 26.6 and 60.5 µM, respectively.

Enhanced production of a novel cytotoxic chromone oxalicumone A by marine-derived mutant Penicillium oxalicum SCSIO 24-2.

Many marine natural products hold great potential for the development of new and much needed drugs. However, the production of active metabolites by marine-derived microorganisms is usually very low, and large-scale culture has to be involved to meet the need of chemical structural modification and deep pharmacy study. In order to enhance the production of a novel cytotoxic sulfur-containing chromone oxalicumone A (OA), germinating spores of a marine-derived wild strain Penicillium oxalicum SCSGAF 0023 were mutated by microwave and ultraviolet light irradiation, which led to the obtainment of a mutant P. oxalicum SCSIO 24-2 that could produce fivefold increase in OA production (3.42 ± 0.21 mg/l) as compared to the wild strain. This is the first report that germinating spores are applied in marine-derived Penicillium sp. mutating to enhance the production of OA. Further, Plackett-Burman design and central composite design were adopted to optimize the basic medium components for increasing OA production by the mutant SCSIO 24-2 in shake flasks. The results indicated that three medium components including mannitol, maltose, and L-cysteine had significant effects on OA production, and their concentrations were optimized as 36, 27.9, and 0.99 g/l, respectively. In the optimized medium, the OA production (18.31 ± 0.27 mg/l) by mutant SCSIO 24-2 was 4.4-fold higher than that in the basic medium. These results of this work promise to improve the present production of OA and may be adopted to enhance other objective products' production by marine-derived fungi.

Cytotoxic dihydrothiophene-condensed chromones from the marine-derived fungus Penicillium oxalicum.

Two new dihydrothiophene-condensed chromones and a new natural chromone, namely oxalicumones A-C (1-3), respectively, were isolated from a culture broth of a marine-derived fungus, Penicillium oxalicum. The structures of 1-3 and acetylated derivatives of 1 (4-7) were elucidated on the basis of spectroscopic methods and chemical reactions. The absolute configuration of 1 and 2 were established by using the modified Mosher ester method and circular dichroism data of an in situ formed [Rh2(OCOCF3)4] and [Mo2(OAc)4] complex. (R)-MTPA ester of 1 showed cytotoxicity against A375, SW-620, and HeLa carcinoma cell lines with IC50 values of 8.9, 7.8, and 18.4 µM, respectively. Compound 1 displayed cytotoxicity against A375 and SW-620 cell lines with IC50 values of 11.7 and 22.6 µM, respectively. The structure-biological activity relationship of 1 was discussed.

Polyketides from a marine-derived fungus Xylariaceae sp.

Eighteen polyketides (1-18) including six citrinin derivatives, two phenol derivatives, one cyclopentenone, two naphthol derivatives, and seven tetralone derivatives were isolated from the culture broth of a marine-derived fungal strain Xylariaceae sp. SCSGAF0086. Five of these compounds (1, 2, 8, 9, and 10) were new, and their structures were determined by spectroscopic methods. Compounds 4, 6, 7, and 17 showed enzyme-inhibitory activities towards several tested enzymes, and 6 and 7 showed strong antifouling activity against Bugula neritina larvae settlement. This is the first time that the antifouling and enzyme-inhibitory activities of these compounds has been reported.

Cytotoxic dihydrothiophene-condensed chromones from marine-derived fungus Penicillium oxalicum.

Two new dihydrothiophene-condensed chromones and a new natural chromone, namely oxalicumones A-C (1-3), respectively, were isolated from a culture broth of a marine-derived fungus Penicillium oxalicum SCSGAF 0023, Meripilaceae family. The structures of 1-3 and acetylated derivatives of 1 (4-7) were elucidated on the basis of spectroscopic methods and chemical reactions. The absolute configuration of 1 was established by using the modified Mosher ester method and circular dichroism data of in situ formed [Rh2(OCOCF3)4] and [Mo2(OAc)4] complexes. (R)-MTPA ester of 1 showed cytotoxicity against A375, SW-620, and HeLa carcinoma cell lines with IC50 values of 8.9, 7.8, and 18.4 µM, respectively. Compound 1 displayed cytotoxicity against A375 and SW-620 cell lines with IC50 values of 11.7 and 22.6 µM, respectively. The structure-biological activity relationship of 1 is discussed.

Three new unsaturated fatty acids from marine-derived fungus Aspergillus sp. SCAU150.

Four unsaturated fatty acid derivatives including three new pantheric acids (1-3), together with three known polyketides (5-7), were isolated from a culture broth of the marine-derived fungus Aspergillus sp. SCAU150. Their complete structures were determined by NMR and HRESIMS data analyses. The antifungal activity of the isolated compounds above was evaluated and 2 was found to show moderated activity toward the phytopathogenic fungus Fusarium solani bio-80814 with an inhibition zone diameter of 6 mm under 5 µg/disc.