8-epi-muralioside, an iridoid glucoside from Linaria arcusangeli

A new polyhydroxylated iridoid glucoside, 1, was isolated from Linaria arcusangeli. The structure of 1 could arise from a regioselective acid-catalyzed-like opening of the epoxide ring of antirrhinoside, the main iridoid constituent of the plant. Compound 1 is the 8-epimer of muralioside, previously isolated from Cymbalaria muralis

ANTIMICROBIAL ACTIVITY OF GINSENOSIDES

The antimicrobial activity of pure ginsenosides (Rb1, Rb2, Rc, Rd, Re, Rg1), two chemical fractions, and the total extract of Panax ginseng root was investigated. The results showed strong antimicrobial activity (minimum inhibitory concentration <1 μg mL−1) by some pure ginsenosides belonging to both protopanaxadiol and protopanaxatriol groups against representative Gram-positive and Gram-negative bacteria, and yeasts. Conversely, Panax ginseng chemical fractions and the total extract were inactive against the microorganisms tested. This lack of antimicrobial activity may be due to possible antagonist effects between ginsenosides and other Panax ginseng components

Intracellular bacteriolysis triggers a massive apoptotic cell death in Shigella-infected epithelial cells

Infected epithelial cells, which act as a first barrier against pathogens, seldom undergo apoptosis. Rather, infected epithelial cells undergo a slow cell death that displays hallmarks of necrosis. Here, we demonstrate that rapid intracellular lysis of Shigella flexneri, provoked by either the use of a diaminopimelic acid auxotroph mutant or treatment of infected cells with antibiotics of the beta-lactam family, resulted in a massive and rapid induction of apoptotic cell death. This intracellular bacteriolysis-mediated apoptotic death (IBAD) was characterized by the specific involvement of the mitochondrial-dependent cytochrome c/Apaf-1 axis that resulted in the activation of caspases-3, -6 and -9. Importantly, Bcl-2 family members and the NF-kappa B pathway seemed to be critical modulators of IBAD. Finally, we identified that [BAD was also triggered by Salmonella enterica serovar Typhimurium but not by the Gram-positive bacteria, Listeria monocytogenes. Together, our results demonstrate that, contrary to previous findings, epithelial cells are intrinsically able to mount an efficient apoptotic cell death response following infection. Indeed, apoptosis in normal circumstances is masked by powerful anti-apoptotic mechanisms, which are overcome in IBAD. Our results also uncover an unexpected consequence of the treatment of infected cells with certain classes of antibiotics. (c) 2008 Elsevier Masson SAS. All rights reserved