Quercetin is a naturally-occurring flavonoid claimed to exert many beneficial health effects. In this report, the influence of quercetin on the surface charge of phosphatidylcholine liposomes and human glioblastoma LN-229 and LN-18 cells was studied using microelectrophoretic mobility measurements. The effect of quercetin on the electrical resistance and capacitance of bilayer lipid membranes was analyzed via electrochemical impedance spectroscopy. The results showed that after flavonoid treatment, the cell lines demonstrated changes in surface charge only in alkaline pH solutions, whereas there were no significant alterations in quercetin-treated vs. control cells in acidic pH solutions. The same tendency was found for liposomal membranes proving that quercetin insertion into membranes is strongly pH-dependent. Capacitance and resistance measurements conducted in acidic electrolyte solutions demonstrated an increase in both electrical parameters, indicating an increased amount of quercetin inserted into the bilayers. Moreover, the cytotoxic effect of quercetin confirms that the flavonoid enters the cells and perturbs the proliferation of LN-229 and LN-18 glioblastoma cell lines. As such, our results indicate that the specific localization of quercetin, membrane-bound or cell-entering, might be crucial for its pharmacological activity. However, further studies are necessary prior to applying these physicochemical measurements as standard methods of evaluating drug activity.

槲皮素是一种天然存在的类黄酮，据称可发挥许多有益的健康作用。在本报告中，使用微电泳迁移率测量研究了槲皮素对磷脂酰胆碱脂质体和人胶质母细胞瘤LN-229和LN-18细胞表面电荷的影响。通过电化学阻抗谱分析了槲皮素对双层脂质膜电阻和电容的影响。结果表明，在类黄酮处理后，细胞系仅在碱性pH溶液中表现出表面电荷变化，而在槲皮素处理后的细胞与对照在酸性pH溶液中相比没有明显变化。对于脂质体膜，发现了相同的趋势，证明槲皮素插入膜中具有强烈的pH依赖性。在酸性电解质溶液中进行的电容和电阻测量结果表明，两个电参数均增加，表明插入双层中的槲皮素数量增加。此外，槲皮素的细胞毒性作用证实类黄酮进入细胞并扰乱LN-229和LN-18胶质母细胞瘤细胞系的增殖。因此，我们的结果表明，槲皮素的特异性定位（膜结合或进入细胞）可能对其药理活性至关重要。但是，在将这些物理化学测量方法用作评估药物活性的标准方法之前，有必要进行进一步的研究。槲皮素的细胞毒性作用证实了类黄酮进入细胞并扰乱了LN-229和LN-18胶质母细胞瘤细胞系的增殖。因此，我们的结果表明，槲皮素的特异性定位（膜结合或进入细胞）可能对其药理活性至关重要。但是，在将这些物理化学测量方法用作评估药物活性的标准方法之前，有必要进行进一步的研究。槲皮素的细胞毒性作用证实了类黄酮进入细胞并扰乱了LN-229和LN-18胶质母细胞瘤细胞系的增殖。因此，我们的结果表明，槲皮素的特异性定位（膜结合或进入细胞）可能对其药理活性至关重要。但是，在将这些物理化学测量方法用作评估药物活性的标准方法之前，有必要进行进一步的研究。