Thielavins W-Z7, New Antifouling Thielavins from the Marine-Derived Fungus Thielavia sp. UST030930-004.

Eleven new depsides-thielavins W-Z (1-4) and thielavins Z1-Z7 (5-11)-and also four known thielavins-A, H, J, and K (12-15)-were isolated from the ethyl acetate extract of a marine-derived fungal strain Thielavia sp UST030930-004. All of these compounds were evaluated for antifouling activity against cyprids of the barnacle Balanus (=Amphibalanus) amphitrite. The results showed that compounds 1-3 and 6-13 were active, with EC50 values ranging from 2.95 ± 0.59 to 69.19 ± 9.51 µM, respectively. The inhibitive effect of compounds 1-3 and 7 was reversible. This is the first description of the antifouling activity of thielavins against barnacle cyprids.

Caspase-3-dependent apoptosis of citreamicin ε-induced HeLa cells is associated with reactive oxygen species generation.

Citreamicins, members of the polycyclic xanthone family, are promising antitumor agents that are produced by Streptomyces species. Two diastereomers, citreamicin ε A (1) and B (2), were isolated from a marine-derived Streptomyces species. The relative configurations of these two diastereomers were determined using NMR spectroscopy and successful crystallization of citreamicin ε A (1). Both diastereomers showed potent cytotoxic activity against HeLa (cervical cancer) and HepG2 (hepatic carcinoma) cells with IC50 values ranging from 30 to 100 nM. The terminal deoxynucleotidyl transferase dUTP nick-end labeling assay confirmed that citreamicin ε A (1) induced cellular apoptosis, and Western blot analysis showed that apoptosis occurred via activation of caspase-3. The 2,7-dichlorofluorescein diacetate assay indicated that citreamicin ε substantially increased the intracellular concentration of reactive oxygen species (ROS). To confirm the hypothesis that citreamicin ε induced apoptosis through an increase in the intracellular ROS concentration, the oxidized products, oxicitreamicin ε A (3) and B (4), were obtained from a one-step reaction catalyzed by Ag2O. These products, with a reduced capacity to increase the intracellular ROS concentration, exhibited a significantly weakened cytotoxicity in both HeLa and HepG2 cells compared with that of citreamicin ε A (1) and B (2).

Four new antibacterial xanthones from the marine-derived actinomycetes Streptomyces caelestis.

Four new polycyclic antibiotics, citreamicin θ A (1), citreamicin θ B (2), citreaglycon A (3), and dehydrocitreaglycon A (4), were isolated from marine-derived Streptomyces caelestis. The structures of these compounds were elucidated by 1D and 2D NMR spectra. All four compounds displayed antibacterial activity against Staphylococcus haemolyticus, Staphylococcus aureus, and Bacillus subtillis. Citreamicin θ A (1), citreamicin θ B (2) and citreaglycon A (3) also exhibited low MIC values of 0.25, 0.25, and 8.0 µg/mL, respectively, against methicillin-resistant Staphylococcus aureus (MRSA) ATCC 43300.

NMR studies on binding sites and aggregation-disassociation of fluorinated surfactant sodium perfluorooctanoate on protein ubiquitin.

The fluorinated surfactant sodium perfluorooctanoate (SPFO) could bind onto ubiquitin (UBQ) and induce the unfolding of UBQ. By using (15)N-edited heteronuclear single-quantum coherence (HSQC) NMR and (19)F NMR to monitor (15)N-labeled UBQ and SPFO, respectively, the binding sites and the aggregation process of SPFO on UBQ at various SPFO concentrations were observed. A detailed process from specific binding to cooperative binding of SPFO on UBQ, and a detailed structure change of UBQ upon the increase of SPFO concentration were obtained. The refolding of UBQ in UBQ-SPFO complex was carried out by adding cationic surfactant. It was shown that added cationic surfactants formed mixed micelles with SPFO and resulted in the dissociation of the UBQ-SPFO complex, and consequently, most ubiquitin could be refolded to its native state.