Inhibitory activity of quercetin and its metabolite on lipopolysaccharide-induced activation of macrophage U937 cells

The potential of quercetin and its metabolite 3-O-methyl quercetin in inhibiting lipopolysaccharide (LPS)-mediated activation of macrophage U937 cells was investigated. Cells were pre-incubated for different periods with 100 ng/mL phorbol myristate acetate (PMA), and later with LPS and quercetin or 3-O-methyl quercetin (30 μM). Later, the supernatant of each cell culture was assessed for catalase activity, nitric oxide, and the production of tumour necrosis factor-α (TNF-α), interleukin 6 (IL-6), and interleukin 1 (IL-1). The results showed that when the cells were incubated with LPS, there were elevations in the levels of all the markers over the cells not incubated with LPS (P < 0.05). For the cells that were incubated with LPS, there were significant differences between the various cells when they were pre-incubated with PMA for various periods (P < 0.05). However, greatest production of the markers was attained when the cells were pre-treated with PMA for 48 h. Both quercetin and 3-O-methyl quercetin (at 30 mM) reduced the levels of all the markers with 3-O-methyl quercetin possessing more inhibitory potential (P < 0.05). This suggests that the flavonoids possessed significant immunomodulatory activities which depend on methylation especially at position 3.     

Quercetin protects embryonic chicken spermatogonial cells from oxidative damage intoxicated with 3-methyl-4-nitrophenol in primary culture

Diesel exhaust particles (DEP) are considered to be one of the most important air pollutants. In this study, the protective effect of quercetin, an antioxidant flavonoid, on oxidative damage of testicular cells was studied by analysis of the intracellular antioxidant system of embryonic chickens after treatment with 3-methyl-4-nitrophenol (PNMC) derived from DEP. Testicular cells from 18-day-old embryos were cultured in serum-free McCoys’5A medium and challenged with PNMC (10⁻⁷ to 10⁻⁵ M) alone or in combinations with quercetin (1.0 μg/ml) for 48 h. Results showed that exposure to PNMC (10⁻⁵ M) induced condensed nuclei and vacuolated cytoplasm, a decrease in testicular cell viability and spermatogonial cell number. Exposure to PNMC induced lipid peroxidation by an elevation of thiobarbituric acid reactive substances as well as decreasing glutathione peroxidation activity and superoxide dismutase activity. However, simultaneous supplementation with quercetin restored these parameters to the similar levels as the control. PNMC is therefore concluded to have induced the oxidative stress of the spermatogonial cells, which can be attenuated by combined quercetin treatment. Our results support the therapeutic use of quercetin in the prevention or treatment of the reproductive toxicity by environmental toxicant PNMC.     

槲皮素对子宫内膜异位症的抑制作用及机理探讨

目的 探讨槲皮素对大鼠子宫内膜异位症模型的异位内膜是否具有抑制作用,以及其抑制作用与热休克蛋白70(HSP70)和血管内皮生长因子(VEGF)表达之间的关系. 方法 通过手术方法 建立大鼠子宫内膜异位症模型,4周后测量异位内膜体积,将造模成功的大鼠分为4组,分别每日灌喂槲皮素、丹那唑、槲皮素+丹那唑以及安慰剂,持续治疗3周后热休克并处死大鼠,测量异位内膜体积并取出异位内膜,检测组织学结构,并采用免疫组化法检测异位内膜组织中HSP70和VEGF的表达. 结果 与安慰剂相比,槲皮素[100 mg/(kg·d)]、丹那唑[36 mg/(kg·d)]和槲皮素+丹那唑联合治疗显著减小了异位内膜的体积,但槲皮素、丹那唑及联合治疗后的异位内膜体积差异无统计学意义.与安慰剂和丹那唑相比,槲皮素和联合治疗明显抑制了异位内膜组织中HSP70和VEGF的表达,且在后两个治疗组中HSP70及VEGF的表达差异无统计学意义. 结论 槲皮素可抑制大鼠子宫内膜异位症模型中异位内膜的生长,并且其抑制效应可能与HSP70和VEGF的表达下降有关,值得进一步研究.     

槲皮素对宫颈癌HeLa细胞nm23基因表达的影响

目的:通过观察槲皮素对宫颈癌HeLa细胞nm23 mRNA的表达水平,分析槲皮素体外诱导HeLa细胞凋亡的机制。方法:按槲皮素浓度分为10,20,40μmol/L和空白对照组、溶剂对照组,分别培养24,48,72 h后,采用逆转录-多聚酶链反应(RT-PCR)方法检测细胞内nm23 mRNA的表达水平。结果:20,40μmol/L槲皮素组在24,48 h时HeLa细胞nm23 mRNA的表达分别较空白对照组、溶剂对照组明显上升(均为P<0.01)。结论:槲皮素可能通过促进转移抑制基因nm23的表达而发挥抗肿瘤作用。     

Anti-proliferative effect of Euphorbia stenoclada in human airway smooth muscle cells in culture

The ethanolic extract of a Malagasy species Euphorbia stenoclada (ES) (Euphorbiaceae), traditionally used as a herbal remedy against asthma and acute bronchitis, was tested to evaluate possible anti-proliferative activity on human airway smooth muscle cells (HASMC). The ES ethanolic extract totally abolished the interleukin-1beta (IL-1beta) induced proliferation of HASMC (IC(50)=0.73+/-0.08 microg/mL). No cytotoxic effect was observed up to 20 microg/mL. A bioassay-guided fractionation of the ethanolic extract was performed by reversed-phase (RP) flash chromatography, giving five fractions (FA to FE) where fraction FE was the only active one (IC(50)=0.38+/-0.02 microg/mL). The purification of this bioactive fraction FE was carried out by RP-HPLC affording six sub-fractions 1-6, and only sub-fraction 5 kept the anti-proliferative activity. Its major constituent was identified as quercetin (IC(50)=0.49+/-0.12 microg/mL) by means of HPLC/UV/MS and co-elution with the authentic standard. Quercitrin was also identified in the fraction FE but was inactive. A structure-activity relationship with flavonols determined that methylation reduced the anti-proliferative activity whereas glycosylation abolished it. The present study shows that the anti-proliferative properties of Euphorbia stenoclada are mediated through the presence of quercetin that may explain the traditional use of this plant as a remedy against asthma.     

The effect of quercetin phase II metabolism on its MRP1 and MRP2 inhibiting potential

The present study characterises the effect of phase II metabolism, especially methylation and glucuronidation, of the model flavonoid quercetin on its capacity to inhibit human MRP1 and MRP2 activity in Sf9 inside-out vesicles. The results obtained reveal that 3'-O-methylation does not affect the MRP inhibitory potential of quercetin. However, 4'-O-methylation appeared to reduce the potential to inhibit both MRP1 and MRP2. In contrast, glucuronidation in general, and especially glucuronidation at the 7-hydroxylmoiety, resulting in 7-O-glucuronosyl quercetin, significantly increased the potential of quercetin to inhibit MRP1 and MRP2 mediated calcein transport with inhibition of MRP1 being generally more effective than that of MRP2. Overall, the results of this study reveal that the major phase II metabolites of quercetin are equally potent or even better inhibitors of human MRP1 and MRP2 than quercetin itself. This finding indicates that phase II metabolism of quercetin could enhance the potential use of quercetin- or flavonoids in general-as an inhibitor to overcome MRP-mediated multidrug resistance.     

Quercetin ameliorates hyperglycemia and dyslipidemia and improves antioxidant status in type 2 diabetic db/db mice

This study investigated the hypoglycemic, hypolipidemic, and antioxidant effects of dietary quercetin in an animal model of type 2 diabetes mellitus. Four-week-old C57BL/KsJ-db/db mice (n = 18) were offered an AIN-93G diet or a diet containing quercetin at 0.04% (low quercetin, LQE) or 0.08% of the diet (high quercetin, HQE) for 6 weeks after 1 week of adaptation. Plasma glucose, insulin, adiponectin, and lipid profiles, and lipid peroxidation of the liver were determined. Plasma glucose levels were significantly lower in the LQE group than in the control group, and those in the HQE group were even further reduced compared with the LQE group. The homeostasis model assessment for insulin resistance (HOMA-IR) showed lower values for LQE and HQE than for the control group without significant influence on insulin levels. High quercetin increased plasma adiponectin compared with the control group. Plasma triglycerides in the LQE and HQE groups were lower than those in the control group. Supplementation with high quercetin decreased plasma total cholesterol and increased HDL-cholesterol compared with the control group. Consumption of low and high quercetin reduced thiobarbituric acid reactive substances (TBARS) levels and elevated activities of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GSH-Px) in the liver. Thus, quercetin could be effective in improving hyperglycemia, dyslipidemia, and antioxidant status in type 2 diabetes.     

Pharmacokinetic-pharmacodynamic indices of enrofloxacin in Escherichia coli O78/H12 infected chickens

Aim of the study was to evaluate the effect of quercetin and enrofloxacin with/without quercetin on elimination of pathogen Escherichia coli O78/H12 in infected chickens. Effect of quercetin on disposition of enrofloxacin was investigated and Pharmacokinetic-pharmacodynamic indices were calculated.Enrofloxacin was absorbed after oral administration in infected animals but with large inter-individual variations. Low concentrations of its main metabolite, ciprofloxacin, were found which could be explained with marked reduction of enrofloxacin transformation in infected animals. Quercetin significantly decreased bioavailability of enrofloxacin and its transformation to ciprofloxacin. Lower formation of metabolite was also found in the studied tissues as spleen, heart, lungs and in liver of group treated in combination with quercetin. Results in infected and quercetin (50 mg/kg) treated group shows lower percentage of re-isolates of the pathogen bacteria in comparison to infected and untreated animals, and close to the low dose (10 mg/kg) of enrofloxacin. High dose of enrofloxacin given in a short time in an infection model with high inoculum size, resulted in better eradication of bacteria although re-isolates could be found in spleen. Additional improvement of the outcome of fluoroquinolone therapy could be searched in early start of drug administration according to the terms of metaphylaxis.     

槲皮素磷脂固体分散体的研制

目的 :研制槲皮素磷脂固体分散体。方法 :应用溶剂挥发法制备不同比例的槲皮素磷脂固体分散体 ,研究其紫外、红外吸收光谱及在水和氯仿中的溶解性。结果 :与槲皮素及其物理混合物相比 ,槲皮素磷脂固体分散体的紫外、红外吸收光谱有明显的变化 ,在水和氯仿中的溶解性显著增大。结论 :槲皮素磷脂固体分散体可增大槲皮素的水溶性和脂溶性 ,有利于生物膜的吸收。     

槲皮素对血管内皮细胞的作用及其机制研究

目的: 观察不同浓度槲皮素对人脐静脉血管内皮细胞（HUVECs）生物学特性的影响,探讨槲皮素抑制血管生成的机制。方法: 应用不同浓度槲皮素处理细胞,在不同时间点,采用CCK-8法检测槲皮素对HUVECs增殖能力的影响;采用细胞划痕实验、基质胶体外成管实验检测槲皮素对HUVECs迁移及形成管腔能力的影响;采用实时荧光定量PCR检测槲皮素对HUVECs中血管内皮细胞因子（VEGF）、碱性成纤维细胞生长因子（bFGF）mRNA表达的影响;采用Western免疫印迹法检测HUVECs中AKT信号通路相关蛋白表达的变化。采用 SPSS 17.0 软件包对数据进行单因素方差分析和Tukey post-hoc分析。结果: 槲皮素能抑制HUVECs的增殖;与对照组相比,槲皮素处理后,HUVECs细胞迁移及形成管腔结构的数量明显减少,抑制作用呈剂量依赖性。槲皮素能抑制HUVECs中VEGF、bFGF mRNA的表达,抑制HUVECs中AKT相关信号通路。结论: 槲皮素抑制HUVECs增殖及体外血管形成能力,其机制部分通过AKT相关信号通路介导。