槲皮素在试管内对血小板功能和膜脂质流动性的影响

本文报道槲皮素对血小板聚集释放反应以及膜脂质流动性的影响。槲皮素浓度为300μmol时对PAF诱导和600μmol时对凝血酶诱导的大鼠血小板聚集几乎完全抑制;也明显地抑制ADP诱导的大鼠血小板聚集及凝血酶诱导的兔血小板~3H-5 HT释放;在槲皮素浓度为30μmol时,即明显降低血小板膜脂质流动性。     

表面活性剂用于黄酮药物的薄层色谱分离鉴定的研究

以表面活性剂的胶束溶液为流动相的胶束色谱技术已引人重视,并已成功地应用于药物的薄层色谱分离鉴定。黄酮类化合物是中草药中广泛存在的一类有效成分。本文以十余种表面活性剂的胶束溶液为流动相研究了槲皮素、桑色素和芦丁的胶束薄层色谱行为,拟出了以4％Zeph—乙酰丙酮—水(5:1.5:1.5)溶液为流动相,聚酰胺薄膜为固定相分离此三种黄酮的层析体系,并对槐花进行分离和鉴定,得到了良好效果。     

槲皮素在体外对NB4细胞形态及VEGF分泌的影响

目的 探讨槲皮素对NB4细胞的形态、血管内皮生长因子（VEGF）表达的影响。方法 以NB4细胞为研究对象,采用Wright染色法观察细胞形态学;Annecxin V标记检测细胞凋亡率;采用ELISA法检测VEGF含量水平。结果 （1）经槲皮素处理后,细胞形态学上出现凋亡特征性改变;（2）槲皮素处理后,NB4细胞凋亡率明显增加;（3）槲皮素处理后,NB4细胞显著降低VEGF的分泌水平。结论 槲皮素在体外能抑制白血病细胞NB4生长并诱导其凋亡;槲皮素可抑制白血病细胞分泌VEGF。     

Quercetin, a flavonoid, inhibits proliferation and increases osteogenic differentiation in human adipose stromal cells

Flavonoids, which have been detected in a variety of foods, have been repeatedly reported to affect bone metabolism. However, the effects of flavonoids on osteoblastogenesis remain a matter of some controversy. In this study, the effects of quercetin on the differentiation and proliferation of human adipose tissue-derived stromal cells (hADSC) were determined. Quercetin was found to increase osteogenic differentiation in a dose-dependent manner. Other flavonoids, chrysin and kaempferol, were also shown to increase the osteogenic differentiation of hADSC, but this stimulatory effect was weaker than that associated with quercetin. Quercetin pretreatment administered prior to the induction of differentiation also exerted stimulatory effects on the osteogenic differentiation of hADSC. RT-PCR and real time PCR analysis showed that quercetin treatment induced an increase in the expression of osteopontin, BMP2, alkaline phosphatase and Runx2. Quercetin inhibited the proliferation of hADSC, but did not affect their survival. The pretreatment of quercetin increased ERK phosphorylation during osteogenic differentiation, although it did not increase ERK activity in control culture condition. ICI182780, an specific estrogen receptor antagonist, failed to inhibit the effects of quercetin on osteogenic differentiation. Quercetin-pretreated hADSC showed better bone regenerating ability in skull defect model of nude mice than naive cells. Our findings indicate that quercetin enhances osteogenic differentiation via an independent mechanism from estrogen receptor (ER) activation, and prove useful for in vivo bone engineering, using human mesencymal stem cells (hMSC).     

Design and synthesis of novel antidiabetic agents

The synthesis and structure-activity relationships of a novel series of substituted quercetins that activates peroxisome proliferator-activated receptor gamma (PPARgamma) are reported. The PPARgamma agonistic activity of the most potent compound in this series is comparable to that of the thiazolidinedione-based antidiabetic drugs currently in clinical use.     

In vivo treatment of acute Chlamydia pneumoniae infection with the flavonoids quercetin and luteolin and an alkyl gallate, octyl gallate, in a mouse model

Increasing evidence suggests that plant polyphenolic compounds may protect from cardiovascular diseases, which have been addressed to their antioxidative properties. In addition, these compounds have been shown to possess anti-inflammatory and anti-microbial potential. In the present study we tested the effects of two flavonoid compounds, quercetin and luteolin, and one alkyl gallate, octyl gallate, on the course of acute Chlamydia pneumoniae infection in vivo. C57BL/6J mice were treated with quercetin, luteolin or octyl gallate for 3 days prior to and 10 days after C. pneumoniae inoculation. Lung tissue was analysed for the presence of chlamydia by culture and quantitative PCR, and inflammatory responses were assessed. Luteolin was found histologically to suppress inflammation in lung tissue, the development of C. pneumoniae-specific antibodies and the presence of chlamydia in lung tissue. Octyl gallate had no significant effect on the course of infection, but quercetin increased both the inflammatory responses and the chlamydial load in the lungs. The infection and inflammation-enhancing effects of quercetin treatment may be attributable to the dose and the route of administration and should be reassessed in further studies with lower doses or with different metabolites of the compound. Contrariwise, the effects of luteolin treatment suggest this compound to have potential in decreasing the infection load and inflammatory reactions in vivo.     

The effect of quercetin on pro-apoptotic activity of cisplatin in HeLa cells

It is well known that some tumour cells are very resistant to chemotherapy-induced cell death which indicate poor prognosis for patients. Thus the aim of the present study was to investigate the effect of quercetin on pro-apoptotic activity of cisplatin in human cervix carcinoma cells (HeLa). Three variants of experiments were performed. In the first one cells were incubated with studied drugs separately for 8 and 24h. In the second, drugs were added to the culture medium simultaneously. In third cisplatin or quercetin addition was followed by subsequent quercetin or cisplatin treatment, respectively. We observed different apoptotic effects, dependent on the drug succession. Preincubation of cells with quercetin followed by cisplatin treatment appeared to be the most effective and was correlated with strong activation of caspase-3 and inhibition of both heat shock proteins (Hsp72) and multi-drug resistance proteins (MRP) levels. Our results indicate that quercetin pretreatment sensitizes HeLa cells to cisplatin-induced apoptosis in HeLa cells.     

Simultaneous determination of quercetin, kaempferol and (E)-cinnamic acid in vegetative organs of Schisandra chinensis Baill. by HPLC

A reversed-phase high-performance liquid chromatographic (RP-HPLC) separation method with UV spectrophotometric detection has been developed for the determination of major components in leaves and caulomas of Schisandra chinensis Baill. The flavonols (quercetin and kaempferol) and (E)-cinnamic acid were analysed after extraction with alcohol from the dry plant material. Identification was based on retention times and UV spectra by comparison with commercial standards. Quercetin, kaempferol and (E)-cinnamic acid were separated within 12 min using acetonitrile–aqueous 0.05% ortho-phosphoric acid (40:60 v/v) mobile phase. The method has been successfully applied for the quantitative analysis of all three major components in several samples from different harvests using propylparaben as the internal standard.     

Dimethyl sulfoxide, but not acidosis-induced metallothionein mRNA expression in neonatal rat primary astrocyte cultures is inhibited by the bioflavonoid, quercetin

Metallothionein (MT) mRNA levels were analyzed following exposure of neonatal rat primary astrocyte cultures to physiologic pH (7.4), acidosis (pH 6.5 and 6.0), and dimethyl sulfoxide (DMSO). Treatments were carried out both in the presence and absence of the bioflavonoid, quercetin. Total RNA was probed on northern blots with [α³²P]dCTP-labeled synthetic cDNA probes specific for rat MT isoform mRNAs. MT-I and MT-II mRNA levels in astrocytes exposed to pH 6.5 or pH 6.0 were increased compared to controls (pH 7.4). Treatment with DMSO in the presence and absence of acidosis, also increased MT-I and MT-II mRNA levels compared to controls (pH 7.4). The DMSO-induced increase in MT mRNA expression was reversed by treatment of astrocytes with quercetin, such that MT-I and MT-II mRNA levels in DMSO plus quercetin-treated astrocytes were indistinguishable from mRNA levels in their respective controls at pH 7.4, pH 6.5, and pH 6.0. These findings suggest that both acidosis and DMSO exposure are associated with increased astrocytic MT synthesis at the mRNA level, and that quercetin, effectively blocks MT mRNA induction by DMSO.     

槲皮素对血小板的抑制作用及其机理分析

作者在以往工作的基础上,采用体内外试验观察了槲皮素对血小板的作用。结果发现,槲皮素可显著抑制二磷酸腺苷、胶原、钙离子载体和花生四烯酸诱导的血小板聚集及血小板5—羟色胺的释放反应;槲皮素能减少血小板血栓烷B_2量、升高6—酮—前列腺素F_(1α)量和6—酮—前列腺素F_(1α)/血栓烷B_2的比值。初步探讨了槲皮素的作用机理,认为其主要是通过影响ADP 和TXA_2途径抑制血小板活化。