高效液相色谱法测定乳舒片中槲皮素含量

目的建立测定乳舒片中槲皮素含量的高效液相色谱法。方法色谱柱：Agilent Eclipse XDB C18（4.6 mm×250 mm,5 μm）,流动相：甲醇－0.2%磷酸水溶液（45：55）,流速1 mL·min 1,检测波长370 nm。结果槲皮素进样量在0.03～0.30 μg范围内具有良好的线性关系（r＝0.999 9）,平均加样回收率99.65%,RSD为1.85%（n＝5）。结论该方法简便、准确,重复性好,可用于控制乳舒片的质量。     

Preparation of amino-modified active carbon cartridges and their use in the extraction of quercetin from Oldenlandia diffusa

Polyethyleneimine (PEI) and ethylenediamine (EDA) as modifiers were bonded on active carbon (AC) surface for specific selective extraction of quercetin from Oldenlandia diffusa. The characteristics of the modified AC materials that were obtained were investigated by field emission-scanning electron microscopy (FE-SEM) and Fourier transform infrared spectrometer (FT-IR). The interactions between quercetin and the AC materials were investigated by fitting the static adsorption data to four linear and nonlinear adsorption isotherm models. Of these four models, the Langmuir-Freundlich adsorption isotherm was proved the best for investigating quercetin on AC materials. Scatchard analysis was used to evaluate the binding properties of the AC materials for quercetin. Solvent extraction and solid-phase extraction (SPE) were optimized, and the effect of the mobile phase pH was investigated to improve the performance for the separation of quercetin on high performance liquid chromatography (HPLC). The results from the validation of the proposed analytical method demonstrated that the EDA-modified AC was the most suitable SPE cartridge for the purification of quercetin from O. diffusa.     

槲皮素抑制人膀胱癌细胞BIU-87生长的作用研究

目的：观察槲皮素对膀胱癌细胞株生长的抑制作用。方法：运用细胞培养、光镜观察及MTT法测定细胞活性等方法,对比膀胱癌细胞在加入不同浓度槲皮素作用后的生长情况和细胞活性,探讨槲皮素对膀胱癌细胞生长的作用。结果：加入不同浓度槲皮素作用一定时间后,膀胱癌细胞的生长受到不同程度的抑制,且具有浓度和时间依赖性。结论：实验证明槲皮素有抑制膀胱癌细胞生长的作用,具有浓度和时间的依赖性。     

槲皮素包合物微球的制备及其体外释放研究

目的:制备槲皮素β-环糊精包合物-壳聚糖微球(QT-CD-CM),并考察其理化性质和药物体外释放性能。方法:采用有机溶剂挥发法制备槲皮素β-环糊精包合物,再用乳化分散-离子交联法、以三聚磷酸钠为交联剂制备壳聚糖微球,并考察其形态、粒径、包封率、载药量和体外释放情况。结果:制备的QT-CD-CM形态规则、均质、无粘连,平均粒径(3.327±0.124)μm,包封率为32.4%,载药量为12.3%,在5%乙醇-磷酸盐缓冲液介质中72h可以达到完全释药,释药过程符合一级动力学模型。结论:QT-CD-CM理化性质及体外释药性能良好,制备工艺简单,有望成为理想的槲皮素给药系统。     

Quercetin regulates oxidized LDL induced inflammatory changes in human PBMCs by modulating the TLR-NF-κB signaling pathway

Toll-like receptors (TLRs) have been shown to play a pivotal role in both innate and adaptive immune responses. TLR family is the essential recognition and signaling component of mammalian host defense. Both genetic and biochemical data support a common signaling pathway that finally leads to the activation of NF-κB and induction of the cytokines and co-stimulatory molecules required for the activation of the adaptive immune response. The present study was designed to examine the involvement of TLR2 and TLR4 in the oxidized LDL induced inflammation in human PBMCs and the effect of flavonoid quercetin on TLR-NF-κB signaling mechanism. LDL was isolated from human plasma and oxidation of LDL was done by incubating with 10 μM CuSO₄ overnight at 37 °C. The isolated human PBMCs in culture were used as the model system. 50 μg/ml ox-LDL treatment significantly up regulated TLR2 and TLR4 expression in isol human PBMCs after 24 h of culture and this was down regulated by quercetin at 25 μM concentration. ox-LDL caused a significant activation of NF-κB as evidenced by the detection of enhanced p65 subunit in nuclear extracts. Supplementation of quercetin significantly modulates the NF-κB p65 nuclear translocation. The cytokine IL-6 production was significantly increased in ox-LDL treated group and was decreased by quercetin treatment. Quercetin mediated reduction of TLR2 and TLR4 expression and the inhibition of nuclear translocation of NF-κB p65 in turn decreased the inflammatory enzymes like 5-LOX and COX and also decreased the mRNA expression of inducible enzymes like COX-2 and iNOS. Quercetin inhibited the ox-LDL induced TLR2 and TLR4 expression at mRNA level and modulated the TLR-NF-κB signaling pathway thereby inhibited the cytokine production and down regulated the activity of inflammatory enzymes thus have protective effect against the ox-LDL induced inflammation in PBMCs.     

Attachment of rhamnosyl glucoside on quercetin confers potent iron-chelating ability on its antioxidant properties

The pharmacological essence of the natural addition of rhamnosyl glucoside on quercetin that is commonly found in nature in medicinal plants is rather obscure. The present study therefore sought to compare the antioxidant activities of both compounds by comparing their ability to decolourise DPPH radicals, reduce Fe³⁺, chelate Fe²⁺, prevent deoxyribose degradation and inhibit hepatic thiobarbituric acid reactive substances induced by both Fe²⁺ and sodium nitroprusside. The results show that quercetin is generally a more potent antioxidant than its rhamnosyl glucoside derivative (rutin). However, rutin exerted a more potent iron-chelating ability than quercetin which diminishes in a time dependent fashion suggesting why it exhibited a reduced inhibitory effect on lipid peroxidation and deoxyribose degradation under harsh prooxidant assault than quercetin. Taken together, we speculate that rutin may have been produced initially in plants as a possible defense mechanism for protection and survival under oxidative assaults and where both flavonoids are found to co-exist in nature, there is a possible synergy in their antioxidant actions.     

槲皮素抑制鱼藤酮诱导的PC12细胞凋亡

目的: 探讨槲皮素对鱼藤酮诱导的PC12细胞凋亡的影响及其作用机制。方法: 运用鱼藤酮诱导损伤PC12细胞,经300 μmol/L槲皮素预处理后,观察细胞形态学改变,流式细胞术检测细胞凋亡率,Western blotting检测Bax和Bcl-2蛋白的表达,JC-1染色检测细胞线粒体膜电位,比较各组的差异。结果: 与鱼藤酮组相比,槲皮素加鱼藤酮处理组细胞形态明显改善,凋亡率降至6.3%(P<0.01),Bcl-2表达增加(P<0.01),Bax表达降低(P<0.01),线粒体膜电位上升(P<0.01)。结论: 槲皮素对鱼藤酮诱导的PC12细胞凋亡具有抑制作用,上调Bcl-2和下调Bax蛋白的表达,维持线粒体膜电位可能是其作用的机制之一。     

Protective effect of quercetin, EGCG, catechin and betaine against oxidative stress induced by ethanol in vitro

There is a need for a nontoxic antioxidant agent to be identified which will prevent alcoholic liver disease (ALD) in alcoholic patients. We tested 4 candidate agents: quercetin, EGCG, catechin and betaine, all of which occur naturally in food. HepG2 cells overexpressing CYP2E1 were subjected to arachidonic acid, iron and 100 mM ethanol with or without the antioxidant agent. All the agents prevented oxidative stress and MDA/4HNE formation induced by ethanol, except for EGCG. Catechin prevented CYP2E1 induction by ethanol. All the agents tended to down-regulate the ethanol-induced increased expression of glutathionine peroxidase 4 (GPX4). All the agents, except catechin, tended to reduce the expression of SOD2 induced by ethanol. Heat shock protein 70 was up-regulated by ethanol alone and betaine tended to prevent this. All 4 agents down-regulated the expression of Gadd45b in the presence of ethanol, which could explain the mechanism of DNA demethylation associated with the up-regulation of the gene expression observed in experimental ALD. In conclusion, the in vitro model of oxidative stress induced by ethanol provided evidence that all 4 agents tested prevented some aspect of liver cell injury caused by ethanol.     

Quercetin Inhibits ��3��4 Nicotinic Acetylcholine Receptor-Mediated Ion Currents Expressed in Xenopus Oocytes

Quercetin mainly exists in the skin of colored fruits and vegetables as one of flavonoids. Recent studies show that quercetin, like other flavonoids, has diverse pharmacological actions. However, relatively little is known about quercetin effects in the regulations of ligand-gated ion channels. In the previous reports, we have shown that quercetin regulates subsets of homomeric ligand-gated ion channels such as glycine, 5-HT_3A and α7 nicotinic acetylcholine receptors. In the present study, we examined quercetin effects on heteromeric neuronal α3β4 nicotinic acetylcholine receptor channel activity expressed in Xenopus oocytes after injection of cRNA encoding bovine neuronal α3 and β4 subunits. Treatment with acetylcholine elicited an inward peak current (I_ACh) in oocytes expressing α3β4 nicotinic acetylcholine receptor. Co-treatment with quercetin and acetylcholine inhibited I_ACh in oocytes expressing α3β4 nicotinic acetylcholine receptors. The inhibition of I_ACh by quercetin was reversible and concentration-dependent. The half-inhibitory concentration (IC₅₀) of quercetin was 14.9±0.8 µM in oocytes expressing α3β4 nicotinic acetylcholine receptor. The inhibition of I_ACh by quercetin was voltage-independent and non-competitive. These results indicate that quercetin might regulate α3β4 nicotinic acetylcholine receptor and this regulation might be one of the pharmacological actions of quercetin in nervous systems.     

Inhibitory Effects of Quercetin on Muscle-type of Nicotinic Acetylcholine Receptor-Mediated Ion Currents Expressed in Xenopus Oocytes

The flavonoid quercetin is a low molecular weight compound generally found in apple, gingko, tomato, onion and other red-colored fruits and vegetables. Like other flavonoids, quercetin has diverse pharmacological actions. However, relatively little is known about the influence of quercetin effects in the regulation of ligand-gated ion channels. Previously, we reported that quercetin regulates subsets of nicotinic acetylcholine receptors such as α3β4, α7 and α9α10. Presently, we investigated the effects of quercetin on muscle-type of nicotinic acetylcholine receptor channel activity expressed in Xenopus oocytes after injection of cRNA encoding human fetal or adult muscle-type of nicotinic acetylcholine receptor subunits. Acetylcholine treatment elicited an inward peak current (I(ACh)) in oocytes expressing both muscle-type of nicotinic acetylcholine receptors and co-treatment of quercetin with acetylcholine inhibited I(ACh). Pre-treatment of quercetin further inhibited I(ACh) in oocytes expressing adult and fetal muscle-type nicotinic acetylcholine receptors. The inhibition of I(ACh) by quercetin was reversible and concentration-dependent. The IC(50) of quercetin was 18.9±1.2 μM in oocytes expressing adult muscle-type nicotinic acetylcholine receptor. The inhibition of I(ACh) by quercetin was voltage-independent and non-competitive. These results indicate that quercetin might regulate human muscle-type nicotinic acetylcholine receptor channel activity and that quercetin-mediated regulation of muscle-type nicotinic acetylcholine receptor might be coupled to regulation of neuromuscular junction activity.