New Polyene Macrolide Compounds from Mangrove-Derived Strain Streptomyces hiroshimensis GXIMD 06359: Isolation, Antifungal Activity, and Mechanism against Talaromyces marneffei.

Mangrove-derived actinomycetes represent a rich source of novel bioactive natural products in drug discovery. In this study, four new polyene macrolide antibiotics antifungalmycin B-E (1-4), along with seven known analogs (5-11), were isolated from the fermentation broth of the mangrove strain Streptomyces hiroshimensis GXIMD 06359. All compounds from this strain were purified using semi-preparative HPLC and Sephadex LH-20 gel filtration while following an antifungal activity-guided fractionation. Their structures were elucidated through spectroscopic techniques including UV, HR-ESI-MS, and NMR. These compounds exhibited broad-spectrum antifungal activity against Talaromyces marneffei with minimum inhibitory concentration (MIC) values being in the range of 2-128 µg/mL except compound 2. This is the first report of polyene derivatives produced by S. hiroshimensis as bioactive compounds against T. marneffei. In vitro studies showed that compound 1 exerted a significantly stronger antifungal activity against T. marneffei than other new compounds, and the antifungal mechanism of compound 1 may be related to the disrupted cell membrane, which causes mitochondrial dysfunction, resulting in leakage of intracellular biological components, and subsequently, cell death. Taken together, this study provides a basis for compound 1 preventing and controlling talaromycosis.

Ursolic acid induces human hepatoma cell line SMMC-7721 apoptosis via p53-dependent pathway.

BACKGROUND: Ursolic acid (UA) is a ubiquitous molecule in the plant kingdom with specific anticancer effects that have been shown in vitro and in vivo. Although UA can inhibit the proliferation of liver cancer cells and induce apoptosis of many types of tumor cells, the molecular mechanism of its anti-hepatoma activity is still not well defined. The objective of this study was to investigate the inhibitory effect and mechanisms of UA on the human hepatoma cell line SMMC-7721. METHODS: After treatment with UA, the growth inhibition of SMMC-7721 cells was assessed by MTT assay. Cells were also evaluated by flow cytometric analysis, Wright-Giemasa staining, Hoechst 33258 staining and transmission electron microscope after they were induced by UA. DNA microarray technology was used to investigate the gene expression pattern of SMMC-7721 cells exposed to UA 40 micromol/L. The molecular mechanism of cells death was analyzed by real-time RT-PCR and Western blotting. RESULTS: The proliferation of SMMC-7721 cells was significantly inhibited in a dose- and time-dependent manner after UA treatment. UA induced cell cycle arrest and apoptosis. The DNA microarray analysis indicated that 64 genes were found to be markedly up- or down-expressed, including GDF15, SOD2, ATF3, and fos. The result of Western blotting showed the apoptotic proteins p53 and Bax were up-regulated while the anti-apoptotic protein Bcl-2 was down-regulated. Real-time RT-PCR confirmed UA could up-regulate the mRNA expressions of GDF15, SOD2, ATF3 and down-regulate the mRAN expression of fos. Meanwhile these effects were partly blocked by pretreatment with the p53 inhibitor Pft-alpha. CONCLUSION: Activation of the p53 pathway is involved in UA inhibition of SMMC-7721 human hepatocellular carcinoma cell growth and induction of apoptosis.