Novel citrinin derivatives from fungus Penicillium sp. TW131-64 and their antimicrobial activities.

Six new citrinin derivatives (1, 2, 4, 10, 11, and 16), along with fourteen known analogues, were acquired from Penicillium sp. TW131-64, a marine-derived fungus strain. The chemical structures of new compounds were identified through adopting various spectroscopic methods in combination with X-ray diffraction technology and comparison of the experimental electronic circular dichroism (ECD) with calculated ones. Among them, compounds 1-4 were nitrogen-containing citrinin derivatives existing in enantiomers which were resolved by chiral chromatography. A putative biosynthetic pathway for compounds 1-4 was proposed. Additionally, the antimicrobial activities of these compounds were detected by the broth microdilution assays. Citrinin derivatives 1, 2, 4 and their corresponding enantiomers (1a, 2a, 4a, 1b, 2b, and 4b) exhibited potent antimicrobial activities towards Helicobacter pylori standard strains and multidrug-resistant strains (MIC values ranging from 0.25 to 8 µg/mL), which were comparable or even better than metronidazole. Moreover, compounds 1a and 1b also showed remarkable broad antimicrobial effects towards Staphylococcus aureus, Enterococcus faecalis, methicillin-resistant Staphylococcus aureus (MRSA), Bacillus subtilis, vancomycin-resistant Enterococcus faecium (VRE), and Candida albicans. In summary, our studies demonstrated that citrinin enantiomers 1a-4a and 1b-4b, especially 1a and 1b, can be lead compounds in the research and development (R & D) of novel antimicrobial drugs. KEY POINTS: • 3 novel nitrogen-containing citrinin derivatives (1, 2, 4) were isolated. • citrinin derivatives 1-4 in enantiomers were resolved by chiral chromatography. • citrinin derivatives 1a and 1b showed broad and significant antimicrobial effects.

New Polyketides from a Hydrothermal Vent Sediment Fungus Trichoderma sp. JWM29-10-1 and Their Antimicrobial Effects.

Marine fungi-derived secondary metabolites are still an important source for the discovery of potential antimicrobial agents. Here, five new polyketides (1, 2, and 6-8) and seven known compounds (3-5 and 9-12) were obtained from the culture of the marine-derived fungus Trichoderma sp. JWM29-10-1. Their structures were identified by extensive spectrographic data analyses, including 1D and 2D NMR, UV, IR, and HR-ESI-MS. Further, the absolute configurations of new compounds were determined by circular dichroism (CD) spectrum and alkali-hydrolysis in combination with the in situ dimolybdenum CD method. Subsequently, the antimicrobial effects of these isolated compounds were assessed by examining the minimal inhibition concentration (MIC) with the broth microdilution assay. Compounds 1 and 2 exhibited potent antimicrobial activity against Helicobacter pylori, including multidrug-resistant strains, with MIC range values of 2-8 µg/mL. Moreover, compound 1 showed significant inhibitory effects on the growth of Gram-positive pathogens, including methicillin-resistant Staphylococcus aureus (MRSA), Enterococcus faecalis, and vancomycin-resistant Enterococcus faecium, which greatly threaten human health. This study demonstrates that chromone derivatives 1-2, especially for 1, could be potential lead compounds for the development of new antimicrobial agents and provides insight for future medicinal chemistry research.

Ag2 O-TiO2 -NTs enhance osteogenic activity in vitro by modulating TNF-α/ß-catenin signaling in bone marrow-derived mesenchymal stem cells.

The toxic effects of nanoparticles-silver oxide (Ag2 O) limited its use. However, loading Ag2 O nanoparticles into titanium dioxide (TiO2 ) nanotubes (Ag2 O-TiO2 -NTs) has more efficient biological activity and safety. The aim of this study was to observe the effect of Ag2 O-TiO2 -NTs on osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) and its mechanism. The enzyme activity of lactate dehydrogenase (LDH) and the expression of RUNX family transcription factor 2 (Runx2), OPN, OCN in BMSCs were detected by quantitative real time polymerase chain reaction. At 14 days of induction, the mineralization ability and alkaline phosphatase (ALP) activity of cells in each group were observed by Alizarin Red S staining and ALP staining. In addition, the protein levels of tumor necrosis factor-α (TNF-α) and ß-catenin in BMSCs of each group were observed by western blot. After 14 days of the induction, the mineralization ability and ALP activity of BMSCs in the Ag2 O-TiO2 -NTs group were significantly enhanced compared with those in the Ag2 O and TiO2 groups. Western blot analysis showed that the BMSCs in the Ag2 O-TiO2 -NTs group exhibited much lower protein level of TNF-α and higher protein level of ß-catenin than those in the Ag2 O and TiO2 groups.Ag2 O-TiO2 -NTs enhance the osteogenic activity of BMSCs by modulating TNF-α/ß-catenin signaling.

Chemistry and bioactivity of marine algal toxins and their geographic distribution in China.

Marine algal toxins are usually produced by some toxic algae during toxic algal blooms which can be accumulated in marine organisms through food chains, leading to contamination of aquatic products. Consumption of the contaminated seafood often results in poisoning in human being. Although algal toxins are harmful for human health, their unique structures and broad spectrum of biological activities have attracted widespread attention of chemists and pharmacologists. Marine algal toxins are not only a reservoir of biological active compound discovery, but also powerful tools for exploring life science. This review first provides a comprehensive overview of the chemistry and biological activities of marine algal toxins, with the aim of providing references for biological active compound discovery. Additionally, typical shellfish poisoning incidents occurred in China in the past 15 years and the geographical distribution of the marine algal toxins in China Sea are discussed, for the purpose of enhancing public awareness of the possible dangers of algal toxins.