桑叶中黄酮化合物的提取工艺及不同品种不同时期的含量变化

探讨了不同单因子对桑叶中黄酮成分浸提效果的影响。用80%乙醇作溶剂,原料质量浓度50.00 g/L,于70℃、pH 8的条件下浸提3 h并抽提2次的提取效果较好。以毛细管电泳仪测定、分析了不同品种、不同时期桑叶中的芦丁、槲皮素等成分,湖桑9001叶片中的芦丁含量高,湖桑32号的槲皮素含量高,10月份采摘桑叶中的芦丁和槲皮素的含量最高。芦丁、槲皮素等成分在桑叶中的动态变化:以10 mmol/L磷酸二氢钠-20 mmol/L的硼砂溶液(pH 8.62)作缓冲液,在25℃,20 kV的压力下电泳,245 nm波长处检测,线性关系良好,在8 m in内完全分离。     

In vitro suppression of quercetin on hypertrophy and extracellular matrix accumulation in rat glomerular mesangial cells cultured by high glucose

Quercetin's protective effects on the glomerulosclerosis of diabetic nephropathy (DN) in rat mesangial cells were investigated. The cell cycles, type IV collagen and laminin, TGF-β₁ mRNA, Smad 2/3 and Smad 7, and activities of cell antioxidases were measured. Compared with the high glucose group, quercetin may decrease the cell percentages of G₀/G₁ phase, Smad 2/3 expression, laminin and type IV collagen, and TGF-β₁ mRNA level significantly. The antioxidant capacity, the cell percentages of S phase and Smad 7 expression was significantly increased by quercetin. These results suggest that quercetin is a protective agent against glomerulosclerosis in DN.     

Effect of quercetin on platelet spreading on collagen and fibrinogen and on multiple platelet kinases

α₂β₁ and α_IIbβ₃ integrins, that support platelet adhesion to collagen and fibrinogen, respectively, share common signaling molecules. The effect of quercetin on platelet static adhesion to collagen and fibrinogen was assessed and correlated with its kinase inhibitory activity. Quercetin strongly abrogated PI3K and Src kinases, mildly inhibited Akt1/2, and slightly affected PKC, p38 and ERK1/2. Quercetin or the combined use of adenosine diphosphate and thromboxane A₂ inhibitors abrogated platelet spreading on these surfaces to a similar extent. We suggest that the inhibitory effect of quercetin on platelet kinases blocks early signaling events preventing a complete platelet spreading.     

Protective effect of quercetin on ER stress-related apoptosis induced by thapsigargin in macrophages

AIM: To investigate the effects and possible mechanisms of quercetin (Que) on endoplasmic reti-culum stress (ERS)-related apoptosis induced by thapsigargin (TG) in RAW264.7 cells. METHODS: ER stress of RAW264.7 cells were induced by TG at concentration of 1 μmol/L for 24 h. After treated with different concentrations of Que (80, 120 and 160 μmol/L), the cell viability was determined by MTT assay.The apoptotic rate and the changes of intracellular Ca²⁺ concentration ([Ca²⁺]_i) were determined by flow cytometry, and the cell apoptotic morphology was observed under laser scanning confocal microscope.The protein levels of glucose-regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP) were detected by Western blotting. The effect of Que on GRP78 and CHOP induced by TG with phosphatidylinositol 3-kinase (PI3K) inihibitor LY294002 at concentration of 15 nmol/L was measured by Western blotting. RESULTS: Que suppressed ER stress-related injury induced by TG in RAW264.7 cells. Compared with TG group, the cell viability increased (P<0.05), apoptotic rate and [Ca²⁺]_i decreased (P<0.05) and the changes of apoptotic morphology were alleviated. The increase in GRP78 and CHOP induced by TG as an ER stress marker was suppressed by Que (P<0.05). The suppressive effect of Que on GRP78 and CHOP was reproduced by LY294002 (P<0.05), but they failed to exhibit additive suppression. CONCLUSION: Que suppresses the ER stress induced by TG in RAW264.7 cells. The protective effect may be related to its suppression on PI3K signaling pathway.     

Simultaneous determination of kaempferol and quercetin in Heteropogon Contortus (L.) Beauv. by validated high-performance thin layer chromatography

Presently, the fingerprint analysis of kaempferol and quercetin has been developed simultaneously via High-Performance Thin Layer Chromatography (HPTLC) from leaves, stem, and inflorescence of Heteropogon contortus. The HPTLC method for kaempferol and quercetin was optimized with the elution of toluene: ethyl acetate: formic acid (7:3:0.5 v/v) as a mobile phase. The fingerprint analysis of kaempferol and quercetin was developed at R_f values of 0.39 and 0.24, respectively, and densitometric evaluation was done at 254 nm. The linear regression data for the calibration curve of both the compounds show a good linear relationship in the concentration range of 2–12 nanogram spot^?1. The suggested method has been validated in terms of limit of detection (LOD) and limit of quantification (LOQ), precision, specificity, sensitivity, and accuracy. Present results show that maximum amount of kaempferol and quercetin is found in leaf extracts (35.80 and 17.01 milligram/gram of dry weight, respectively) of H. contortus.     

Vitamin C and quercetin modulate DNA-damaging effect of N-methyl-N′-nitro-N-nitrosoguanidine (MNNG)

The effects of natural compounds, vitamin C and quercetin, present in fruitsand vegetables, on the DNA damaging activity of a food carcinogen N-methyl-N-nitro-N-nitrosoguanidine (MNNG) were examinedusing the comet assay. Vitamin C, at a concentration of 50 M,inhibited MNNG-induced DNA damage in human lymphocytes. Quercetin,up to a concentration of 10 M, increased the extent of DNA damage,but at concentrations above 10 M decreased damage below controlvalues. Furthermore, quercetin had a strong antioxidant activity againstoxidative damage evoked by H₂O₂ at 10 M. The resultsobtained suggest that vitamin C and quercetin may have anti- orpro-oxidative properties depending on the state of the cell.     

植物雌激素槲皮素对非洲爪蟾生长和骨骼发育的影响

用两栖动物非洲爪蟾作模型动物,来揭示植物雌激素槲皮素对非洲爪蟾生长和骨骼发育的影响。非洲爪蟾从46/47期开始,分别暴露50μg/L,100μg/L,200μg/L槲皮素,直至变态后1个月。结果表明槲皮素处理一方面促进蝌蚪体重的增加,另一方面导致尾的畸形。200μg/L槲皮素还导致脊柱的畸形,表现为少一块脊椎骨。     

大麦籽粒中4种主要黄酮类化合物的HPLC测定方法研究

为给大麦主要黄酮类化合物含量的快速测定及开发利用提供依据,对利用高效液相色谱技术(HPLC)分离和同时测定大麦中黄酮类化合物儿茶素、杨梅素、槲皮素、山奈酚含量的方法进行了研究.结果表明,采用HPLC同时测定4种大麦黄酮类化合物的优化色谱条件为:YMC-Pack ODS AM-303 (5 μm, 250 mm_4.6 mm i.d.)色谱柱;流动相A-0.1%冰乙酸水溶液,B-乙睛,梯度洗脱;流速0.8 mL/min,进样量10 μL.儿茶素、杨梅素、槲皮素、山奈酚分别在0.063～2.000 μg (R2=0.9999)、0.034～1.100 μg (R2=0.9998)、0.025～0.800 μg (R2=0.9993)、0.018～0.560 μg (R2=0.9995)成良好的线性关系,加样回收率分别为96.88%(RSD=1.30%)、98.30%(RSD=0.57%)、96.29%(RSD=1.20%)、101.59%(RSD=0.73%). 测定方法简便、快捷,结果准确、重复性好,可用于大麦4种主要黄酮类化合物的同时测定.     

Subacute chlorpyrifos-induced oxidative stress in rat erythrocytes and the protective effects of catechin and quercetin

This study examined the effects of chlorpyrifos in the rat erythrocyte antioxidant system and evaluated the ameliorating effects of catechin and quercetin on the oxidative damage induced by chlorpyrifos. Sexually mature male Wistar rats were given chlorpyrifos (5.4 mg/kg, 1/25 of the oral LD₅₀), catechin (20 mg/kg), quercetin (20 mg/kg), catechin plus chlorpyrifos, and quercetin plus chlorpyrifos daily via gavage for four weeks. No statistical differences were found in the catechin-only and quercetin-only groups compared with the control group. By the end of the fourth week, chlorpyrifos alone increased the levels of malondialdehyde (MDA) and decreased superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GPx) activities compared with the control group in rat erythrocytes. In the catechin-plus-chlorpyrifos and quercetin-plus-chlorpyrifos groups, there were statistically significantly decreased MDA levels and increased SOD, CAT, and GPx activities compared with the chlorpyrifos-only group. Thus, it appears that catechin and quercetin ameliorate chlorpyrifos-induced oxidative stress in rat erythrocytes in vivo.     

Quercetin Promotes Auxin Transport in Arabidopsis thaliana

Study on the role of quercentin in polar auxin transportation. Arabidopsis was cultured on medium supplemented with quercetin to observe the growth of hypocotyls, 14C-IAA transport assays were conducted to measure the auxin transport activity. The results showed that Arabidopsis mutant auxl which had been deficient in auxin influx transportion obviously recovered the ability after cultured on the medium with quercetin. The polar auxin transport was promoted by the addition of quercetin. These results indicated that quereetin could promote polar auxin transport in vivo.