Amentoflavone inhibits hepatitis B virus infection via the suppression of preS1 binding to host cells.

Hepatitis B virus (HBV) is a leading cause of chronic hepatitis, liver cirrhosis, and hepatocellular carcinoma. Current therapeutic drugs for chronic HBV infection use IFN and nucleos(t)ide analogs; however, their efficacy is limited. Thus, there is an urgent need to develop new antivirals for HBV therapy. In this study, we identified a plant-derived polyphenolic bioflavonoid, amentoflavone, as a new anti-HBV compound. Amentoflavone treatment dose-dependently inhibited HBV infection in HBV-susceptible cells with HepG2-hNTCP-C4 and primary human hepatocyte PXB-cells. A mode-of-action study showed that amentoflavone inhibits the viral entry step, but not the viral internalization and early replication processes. Attachment of HBV particles as well as HBV preS1 peptide to HepG2-hNTCP-C4 cells was inhibited by amentoflavone. The transporter assay revealed that amentoflavone partly inhibits uptake of sodium taurocholate cotransporting polypeptide (NTCP)-mediated bile acid. Furthermore, effect of various amentoflavone analogs on HBs and HBe production from HBV-infected HepG2-hNTCP-C4 cells was examined. Robustaflavone exhibited comparable anti-HBV activity to that of amentoflavone and an amentoflavone-7,4', 4‴-trimethyl ether derivative (sciadopitysin) with moderate anti-HBV activity. Cupressuflavone or the monomeric flavonoid apigenin did not exhibit the antiviral activity. Amentoflavone and its structurally related biflavonoids may provide a potential drug scaffold in the design of a new anti-HBV drug inhibitor targeting NTCP.

Rapid Fluorescence Quenching Detection of Escherichia coli Using Natural Silica-Based Nanoparticles.

The development of fluorescent silica nanoparticles (SNP-RB) from natural amorphous silica and its performance as an Escherichia coli (E. coli) biosensor is described in this paper. SNP-RB was derived from silica recovered from geothermal installation precipitation and modified with the dye, Rhodamine B. The Fourier Infrared (FTIR) confirms the incorporation of Rhodamine B in the silica matrix. Transmission Electron Microscopy (TEM) micrographs show that the SNP-RB had an irregular structure with a particle diameter of about 20-30 nm. The maximum fluorescence spectrum of SNP-RB was recorded at 580 nm, which was further applied to observe the detection performance of the fluorescent nanoparticles towards E. coli. The sensing principle was based on the fluorescence-quenching mechanism of SNP-RB and this provided a wide linear E. coli concentration range of 10-105 CFU/mL with a limit detection of 8 CFU/mL. A rapid response time was observed after only 15 min of incubation of SNP-RB with E. coli. The selectivity of the biosensor was demonstrated and showed that the SNP-RB only gave quenching response only to live E. coli bacteria. The use of SNP-RB as a sensing platform reduced the response time significantly compared to conventional 3-day bacterial assays, as well having excellent analytical performance in terms of sensitivity and selectivity.

Effect of media compositions on α-glucosidase inhibitory activity, growth and fatty acid content in mycelium extracts of Colletotrichum sp. TSC13 from Taxus Sumatrana (Miq.) de Laub.

The active α-glucosidase inhibitor compounds in the endophytic fungus Colletotrichum sp. TSC13 were found to be the unsaturated fatty acids (oleic, linoleic and linolenic acids). These compounds have potential as antidiabetic agents. The aim of the present study is to investigate the effects of various media composition on growth (mycelium dry weight) and the fatty acids content (µg mg(-1) mycelium DW) of Colletotrichum sp. TSC13 in relation to its α-glucosidase inhibitory activity. For that purpose, the experiments were set up by varying the carbon and nitrogen sources, metal ions and desaturase and fatty acid synthase inhibitors in the media. Colletotrichum sp. TSC13 grown on potato dextrose broth (PDB) was used as control. The α-glucosidase inhibitory activities were (range from 43.9 ± 2.5 to 88.6 ± 5.2%) at 10 µg mL(-1). This activity seemed to correlate with the unsaturated fatty acids content of the samples. Different sugars as carbon source experiment showed that xylose gave the highest growth (938.7 ± 141.6 mg). However, the highest fatty acids content was obtained from fructose medium which containing linoleic acid (38.8 ± 4.9 µ g mg(-1) DW). Soluble starch gave better growth (672.5 ± 62.3 mg) but very low fatty acids content (2.8 ± 0.1 µg mg(-1) DW) was obtained. Yeast extract was the best nitrogen source. Fatty acids production was better as compared to beef extract and soytone. This is the first report of various media compositions on fatty acids content in Colletotrichum sp. TSC13 in relation to its α-glucosidase inhibitory activity.

Isolation of alpha-glucosidase inhibitors produced by an endophytic fungus, Colletotrichum sp. TSC13 from Taxus sumatrana.

Colletotrichum sp. have potential to act as antidiabetic agent, due to its alpha-glucosidase inhibitory. Therefore, the objective of present study was to isolate and identify the bioactive compounds responsible for the alpha-glucosidase inhibitory activity in Colletotrichum sp. TSC13. The methanol extract of TSC13 mycelia, was partitioned with n-hexane, chloroform and ethyl acetate. The n-hexane fraction exhibited the strongest alpha-glucosidase inhibitory activity. Column chromatography of this fraction resulted in 8 sub-fractions (F1-8). Fraction 3 (F3) which showed 71.4 +/- 2.4% inhibition was analysed further. Analysis using GC-MS after methylation of F3 and comparison to spectra databases and confirmation using authentic sample standards showed that F3 had two saturated fatty acid methyl esters, palmitic acid and stearic acid methyl esters and three unsaturated fatty acid methyl esters, oleic acid, linoleic acid and linoleinic acid methyl esters. Unsaturated fatty acids showed higher activity than the saturated fatty acids and the methyl esters form of unsaturated fatty acids showed slightly less active than the free acids. Further analysis using an ethyl acetate extract, it was confirmed that most of the fatty acids were present in the form of free acids. Therefore, it was concluded that the alpha-glucosidase inhibitor compounds in Colletotrichum sp. TSC13 were unsaturated fatty acids. This is the first report that a Colletotrichum sp. from T. sumatrana has alpha-glucosidase inhibitory activity.