Concentration dependence of the blockade of nicotinic receptor-mediated currents by (+)-erythravine.

<p>A. Currents elicited by 2-s pulses of acetylcholine 50 µM (blue bars) in a representative HEK 293 cell expressing α4β2 receptors in the presence of increasing concentrations of (+)-erythravine (0.003 to 1 µM; red bars). <b>B.</b> Currents elicited by 0.5 s pulses of acetylcholine 300 µM (blue bars) in a representative hippocampal neuron expressing α7* receptors in the presence of increasing concentrations of (+)-erythravine (0.3 to 100 µM; red bars). The alkaloid was pre-applied on the bathing solution and was in equilibrium during the agonist pulse. <b>C</b>. Concentration-response curves showing the area under the current traces obtained as in <b>A</b> and <b>B</b>. Non-linear regression using the Hill equation yielded an IC₅₀ of 4 nM and a Hill coefficient of ­–0.6 for α4β2 receptors (empty circles) and an IC₅₀ of 6 µM and a Hill coefficient of ­–0.5 for native α7* receptors (filled triangles). Data are presented as means ± SEM (n  =  3 cells).</p

Screening of the <i>Erythrina</i> alkaloids.

<p>A. Hippocampal neurons constitutively expressing α7* nicotinic receptors. Currents elicited by 0.5-s pulses of acetylcholine 100 µM (blue bars) were partially and reversibly blocked by co-application with 100 µM of (+)-11α-hydroxyerysotrine, (+)-erythravine and (+)-11α-hydroxyerythravine (red bars). Membrane potentials were fixed at –67 mV. <b>B.</b> HEK 293 cells heterologously expressing α4β2 nicotinic receptors. Currents elicited by 2-s pulses of acetylcholine 50 µM (blue bars) were partially and reversibly blocked by co-application with 10 µM of (+)-11α-hydroxyerysotrine, (+)-erythravine and (+)-11α-hydroxyerythravine (red bars). Membrane potentials were fixed at –87 mV. <b>C.</b> PC12 cells constitutively expressing α3* nicotinic receptors. Currents elicited by 0.5 s pulses of acetylcholine 100 µM (blue bars) were partially and reversibly blocked by co-application with 50 µM of (+)-11α-hydroxyerysotrine, (+)-erythravine and (+)-11α-hydroxyerythravine (red bars). Membrane potentials were fixed at –87 mV. All experiments were performed in the presence of 0.15 µM of TTX (only in experiments with neurons) and 0.5 µM of atropine sulfate. Traces are representative of 3 to 5 independent cells and the mean responses are shown in the bar graphs to the right as the percentages of the current obtained from the first acetylcholine pulse, with error bars being the SEM. Black bars represent the current at peak and grey bars represent the area under the trace for a period of 1.5 s for α4β2 HEK 293 cells and PC12 cells and 1 s for hippocampal neurons, starting at the beginning of the agonist pulse. HEt, (+)-11α-hydroxyerysotrine; Ev, (+)-erythravine; HEv, (+)-11α-hydroxyerythravine.</p

Structures of the alkaloids from <i>E. mulungu</i>.

<p>Structures of the alkaloids from <i>E. mulungu</i>.</p

General pathways for phenol derivatives as (a) antioxidant or (b) pro-oxidant.

<p>General pathways for phenol derivatives as (a) antioxidant or (b) pro-oxidant.</p

Apocynin versus P7 as pro-oxidants. (a) Oxidation of trolox, (b) oxidation of NADH and (c) oxidation of GSH.

<p>When present, apocynin and P7 were added at 5 µM. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110277#s2" target="_blank">material and methods</a> for further experimental details. Data represent the mean and SD of three experiments. *p<0.05 relative to control.</p

The length of the protocatechuate's carbon chain and the rate of oxidation of trolox.

<p>(a) The reaction mixture consisted of 100 µM trolox, 0.01 µM HRP and 50 µM H₂O₂ in the absence (control) or presence (2 µM) of the tested compounds. (b) Rate of oxidation. Data represent the mean and SEM of three experiments. *p<0.05 relative to the control. (c) Effect of the concentration of P7 on the rate of oxidation (r²  = 0.9766).</p

The length of a protocatechuate's carbon chain and the rate of oxidation of rifampicin.

<p>(a) The reaction mixture consisted of 100 µM rifampicin, 0.01 µM HRP, and 50 µM H₂O₂ in the absence (control) or presence (2 µM) of the tested compounds. (b) Reaction rate. Data represent the mean and SD of three experiments. *p<0.05 relative to the control.</p

Oxidation of α-tocopherol and the effect of P0 and P7.

<p>The reaction mixture consisted of 100 µM α-tocopherol, 0.01 µM HRP, 50 µM H₂O₂ and 5 µM of the tested compounds. The reactions were stopped after 10 min and injected into the HPLC. See <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0110277#s2" target="_blank">materials and methods</a> for further experimental details. The control is a standard of α-tocopherol (100 µM).</p

Differential pulse voltammograms of 0.1 mM solutions of heptyl protocatechuate and apocynin at pH 7.0.

<p>Differential pulse voltammograms were obtained at modulation time 0.05 s, pulse amplitude 0.05 V, step potential 0.45 mV and scan rate 4.5 mV/s.</p

Biologically Active Eremophilane-Type Sesquiterpenes from <i>Camarops</i> sp., an Endophytic Fungus Isolated from <i>Alibertia macrophylla</i>

Two new eremophilane-type sesquiterpenes, xylarenones F (<b>3</b>) and G (<b>4</b>), have been isolated from solid substrate cultures of a <i>Camarops</i> sp. endophytic fungus isolated from <i>Alibertia macrophylla</i>, together with the known compounds xylarenones C (<b>1</b>) and D (<b>2</b>). The structures and relative configurations of <b>1</b>–<b>4</b> were elucidated by extensive NMR and HRESIMS spectroscopic analysis. Due to their effects on the respiratory burst of neutrophils, which included inhibition of the reactive oxygen species production, these sesquiterpenes exhibited potential anti-inflammatory and antioxidant properties