Study on antioxidant activity of flavonoids from leaves of Psidium guajava / 中国中药杂志

The present study is to study the chemical constituents from ethanol extract of Psidium guajava leaves. The constituents were separated and purified by silica gel column chromaiographios over, macroporous resin D-101, Sephadex LH-20, and ODS. Six flavonoids compounds were isolated and identified as quercetin(1), quercetin-3---D-arabinopyranoside(2), quercetin-3---D-ribopyranoside(3), quercetin-3---D-galactopyranoside(4), quercetin-3---D-glucopyranoside(5), and quercetin-3--D-xylpyranoside(6). The antioxidant effects of six flavonoids was evaluated by scavenging ability of DPPH, superoxide anion, ABTS·⁺, and reducing effect of Fe³⁺ as well as total antioxidant capacity(FRAP). Vitamin C was used as positive control. The results indicated that six flavonoids exhibited significant antioxidant effects.

Hemodynamic effects of stenting on wide-necked intracranial aneurysms / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Stent placement has been widely used to assist coiling in cerebral aneurysm treatments. The present study aimed to investigate the hemodynamic effects of stenting on wide-necked intracranial aneurysms.</p><p><b>METHODS</b>Three idealized plexiglass aneurismal models with different geometries before and after stenting were created, and their three-dimensional computational models were constructed. Flow dynamics in stented and unstented aneurismal models were studied using in vitro flow visualization and computational fluid dynamics (CFD) simulations. In addition, effects of stenting on flow dynamics in a patient-specific aneurysm model were also analyzed by CFD.</p><p><b>RESULTS</b>The results of flow visualization were consistent with those obtained with CFD simulations. Stent deployment reduced vortex inside the aneurysm and its impact on the aneurysm sac, and decreased wall shear stress on the sac. Different aneurysm geometries dictated fundamentally different hemodynamic patterns and outcomes of stenting.</p><p><b>CONCLUSIONS</b>Stenting across the neck of aneurysms improves local blood flow profiles. This may facilitate thrombus formation in aneurysms and decrease the chance of recanalization.</p>