Diterpenoids from Sauropus spatulifolius Leaves with Antimicrobial Activities.

As a plant used in both food and medicine, Sauropus spatulifolius is consumed widely as a natural herbal tea, food source, and Chinese medicine. Inspired by its extensive applications, we conducted a systematic phytochemical study of the leaves of S. spatulifolius. Thirteen new diterpenoids, sauspatulifols A-M (1-13), including four ent-cleistanthane-type diterpenoids (1-4), eight 15,16-di-nor-ent-cleistanthane-type diterpenoids (5-12), and one 17-nor-ent-pimarane-type diterpenoid (13) as well as one known diterpenoid, cleistanthol (14), were isolated. All of these diterpenoids feature a 2α,3α-dihydroxy unit within the A ring, and their structures were elucidated by spectroscopic data analysis, electronic circular dichroism calculations, and single-crystal X-ray diffraction analysis. Compound 14 displayed moderate inhibitory activity against Staphylococcus aureus, Staphylococcus epidermidis, Bacillus subtilis, and Shigella flexneri with the same minimum inhibitory concentration value of 12 µg/mL as well as activity against vesicular stomatitis virus and influenza A virus.

Hepatitis C virus inhibits intracellular interferon alpha expression in human hepatic cell lines.

The chronicity of hepatitis C virus (HCV) infection raises the question of how HCV is able to persist in hepatic cells. We show that human primary hepatocytes and human hepatic cell lines (Huh7 and HepG2) spontaneously produce interferon (IFN)-alpha that is inhibited in the HCV replicon cells (Huh.8 and FCA-1). Silencing IFN-alpha gene expression by IFN-alpha small interfering RNA (siRNA) in the HCV replicon cells resulted in increased HCV replicon expression. The activation of IFN-alpha expression by interferon regulatory factor (IRF-7) led to the inhibition of HCV replicon expression, whereas the anti-IFN-alpha receptor antibody could partially block IRF-7-mediated HCV replicon inhibition. In addition, the blockade of IFN-alpha receptor by anti-IFN-alpha receptor antibody on the replicon cells increased HCV replicon expression. Among the HCV nonstructural (NS) proteins tested, NS5A is the most potent inhibitor of IFN-alpha expression by the hepatic cells. Investigation of the mechanism of HCV action on IFN-alpha showed that IRF-7-induced IFN-alpha promoter activation was inhibited in the HCV replicon cells. Furthermore, IRF-7 expression was restricted in the HCV replicon cells. In conclusion, we provide direct evidence that HCV undermines the intracellular innate immunity of the target cells, which may account for HCV persistence in hepatic cells.

Structure of the Lrp-regulated serA promoter of Escherichia coli K-12.

Expression of the Escherichia coli serA gene is activated in vivo by the product of the lrp gene, leucine-responsive regulatory protein (Lrp), an effect partially reversed by L-leucine. We show here that serA is transcribed from two promoters, P1 45 bp upstream of the translation start site, and P2 92 bp further upstream. Lrp binds to a long AT-rich sequence from -158 to -82 from the start of the coding region, i.e. upstream of P1 and overlapping P2. It activates transcription from P1 and represses expression from P2. A second regulator, cAMP/CRP, activates P2, an effect that is largely inhibited by Lrp, such that catabolite repressor protein (Crp) and Lrp are rival activators of serA transcription.