Inhibition of nitric oxide synthase inhibitors and lipopolysaccharide induced inducible NOS and cyclooxygenase-2 gene expressions by rutin, quercetin, and quercetin pentaacetate in RAW 264.7 macrophages

Several natural flavonoids have been demonstrated to perform some beneficial biological activities, however, higher-effective concentrations and poor-absorptive efficacy in body of flavonoids blocked their practical applications. In the present study, we provided evidences to demonstrate that flavonoids rutin, quercetin, and its acetylated product quercetin pentaacetate were able to be used with nitric oxide synthase (NOS) inhibitors (N-nitro-L-arginine (NLA) or N-nitro-L-arginine methyl ester (L-NAME)) in treatment of lipopolysaccharide (LPS) induced nitric oxide (NO) and prostaglandin E2 (PGE2) productions, inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) gene expressions in a mouse macrophage cell line (RAW 264.7). The results showed that rutin, quercetin, and quercetin pentaacetate-inhibited LPS-induced NO production in a concentration-dependent manner without obvious cytotoxic effect on cells by MTT assay using 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide as an indicator. Decrease of NO production by flavonoids was consistent with the inhibition on LPS-induced iNOS gene expression by western blotting. However, these compounds were unable to block iNOS enzyme activity by direct and indirect measurement on iNOS enzyme activity. Quercetin pentaacetate showed the obvious inhibition on LPS-induced PGE2 production and COX-2 gene expression and the inhibition was not result of suppression on COX-2 enzyme activity. Previous study demonstrated that decrease of NO production by L-arginine analogs effectively stimulated LPS-induced iNOS gene expression, and proposed that stimulatory effects on iNOS protein by NOS inhibitors might be harmful in treating sepsis. In this study, NLA or L-NAME treatment stimulated significantly on LPS-induced iNOS (but not COX-2) protein in RAW 264.7 cells which was inhibited by these three compounds. Quercetin pentaacetate, but not quercetin and rutin, showed the strong inhibitory activity on PGE2 production and COX-2 protein expression in NLA/LPS or L-NAME/LPS co-treated RAW 264.7 cells. These results indicated that combinatorial treatment of L-arginine analogs and flavonoid derivates, such as quercetin pentaacetate, effectively inhibited LPS-induced NO and PGE2 productions, at the same time, inhibited enhanced expressions of iNOS and COX-2 genes.     

Flavonoid chemistry of Chenopodium fremontii. Infraspecific variation and systematic implications at the interspecific level

Four flavonoid geographical races based on twenty flavonol 3-O-glycosides were found to exist in Chenopodium fremontii with those populations from the northern part of the range (northern Colorado, Wyoming. and western Nebraska) producing 7-methyl ethers and 3-O-galactosides and glucosides. Plants from Arizona. southern Colorado and New Mexico lack 7-methyl ethers and contain 3-O-rhamnogalactosides and rhamnoglucosides (rutinosides). California populations are chemically similar to those from Arizona, southern Colorado and New Mexico but contain arabinosides while lacking rutinosides. No morphological features could be correlated with the chemical races. Chenopodium fremontii can be distinguished chemically from other closely related diploid species of the western U.S., all of which exhibit simpler flavonoid patterns. It is suggested that the simpler chemical patterns for the latter species (which include C. atrovirens, C. desiccatum, C. hians. C. incanum, C. leptophyllum, and C. pratericola) are a derived condition relative to C. fremontii.     

Quercetin Enhances Cisplatin Sensitivity of Human Osteosarcoma Cells by Modulating microRNA-217-KRAS Axis

Quercetin can suppress osteosarcoma cell growth and metastasis. However, other effects of quercetin on osteosarcoma remain largely unknown. This research aims to evaluate the effects of quercetin in combination with cisplatin as treatment for osteosarcoma and investigate its regulatory mechanism. Cell viability and apoptosis in 143B cell line were determined after treatment with quercetin and/or cisplatin. RT-PCR and Western blot analysis were performed to determine the RNA or protein expression levels. Moreover, transwell assay was used to evaluate metastasis. Furthermore, rescue experiments were performed to investigate the potential regulatory mechanism of the treatment. Results showed that quercetin with concentration that was equal to or greater than 10 μM inhibited 143B proliferation, while 5 μM quercetin enhanced the cisplatin sensitivity of 143B cells. Expression of miR-217 was upregulated after quercetin and/or cisplatin treatment, while its target KRAS was downregulated both at mRNA and protein levels. MiR-217 knockdown led to the loss of enhanced cisplatin sensitivity while miR-217 overexpression showed the opposite effects, indicating that quercetin regulated cisplatin sensitivity by modulating the miR-217-KRAS axis. In conclusion, 5 μM quercetin enhanced the cisplatin sensitivity by modulating the miR-217-KRAS axis. This finding suggests that quercetin may be administered with cisplatin to improve the treatment for osteosarcoma.     

Quercetin 3-O-β-glucoside is better absorbed than other quercetin forms and is not present in rat plasma

The effect of the nature of the sugar moiety on quercetin absorption has been investigated in rats. Four groups of rats received an experimental meal containing 20 mg of quercetin equivalents, supplied as quercetin, quercetin 3-O-β-glucoside, quercetin 3-O-β-rhamnoside or rutin. Four hours after the meal, the metabolites identified in hydrolysed plasma were identical in all groups (3′- and 4′-methylquercetin). However, the total concentration of metabolites was markedly different: 11.2±1.8, 2.5±2.0 and 33.2±3.5 μM for the quercetin, rutin, and quercetin 3-glucoside meals respectively. After quercetin 3-rhamnoside consumption, we failed to detect any metabolites in the plasma. These data suggest that the 3-O-glucosylation improves the absorption of quercetin in the small intestine, whereas the binding of a rhamnose to the aglycone markedly depresses it. Additional experiments have shown that the higher plasma levels measured after quercetin 3-glucoside meal compared to the quercetin meal were maintained throughout the 24-hour period following the meal. Using a multi-electrode coulometric detection, together with suitable chromatographic conditions, we were able to distinguish between the conjugated and the glycosylated forms. Thus, we clearly showed the absence of quercetin 3-O-β-glucoside in the plasma from rats fed a diet containing this glucoside. This result suggests that quercetin 3-O-β-glucoside is hydrolysed before or during its intestinal absorption.     

Activities of muscadine grape skin and quercetin against Helicobacter pylori infection in mice

Aims: To explore the preventative potential of muscadine grape skin (MGS) and the single flavonoid, quercetin, as an alternative means for ameliorating Helicobacter pylori infection and/or the H. pylori‐induced inflammatory response in mice. Methods and Results: The antimicrobial and anti‐inflammatory properties of MGS and quercetin, a major phenolic constituent, were evaluated against H. pylori in vitro and in vivo. The antimicrobial activity of quercetin was evaluated against 11 H. pylori strains in vitro with inhibition of all strains at 128–64 μg ml^?1. In vivo studies showed a moderate reduction in H. pylori counts following treatment with 5 and 10% MGS or quercetin (25 mg kg^?1 body weight) in addition to significantly reduced inflammatory cytokines (TNF‐α, IL‐1β and IFN‐γ) when compared with untreated mice. Conclusions: MGS and quercetin did not significantly reduce H. pylori growth in a mouse model. However, these products were effective in regulating the inflammatory response to H. pylori infection. Significance and Impact of the Study: Our results suggest that H. pylori infection may be reduced or prevented via the consumption of fruits rich in certain phenolic compounds (e.g. quercetin) such as muscadine grapes.     

Quercetin protects rats from catheter‐related Staphylococcus aureus infections by inhibiting coagulase activity

Coagulase (Coa) activity is essential for the virulence of Staphylococcus aureus (S aureus), one of the most important pathogenic bacteria leading to catheter‐related bloodstream infections (CRBSI). We have demonstrated that the mutation of coagulase improved outcomes in disease models of S aureus CRBSI, suggesting that targeting Coa may represent a novel antiinfective strategy for CRBSI. Here, we found that quercetin, a natural compound that does not affect S aureus viability, could inhibit Coa activity. Chemical biological analysis revealed that the direct engagement of quercetin with the active site (residues Tyr187, Leu221 and His228) of Coa inhibited its activity. Furthermore, treatment with quercetin reduced the retention of bacteria on catheter surfaces, decreased the bacterial load in the kidneys and alleviated kidney abscesses in vivo. These data suggest that antiinfective therapy targeting Coa with quercetin may represent a novel strategy and provide a new leading compound with which to combat bacterial infections.     

栎皮酮对甜菜夜蛾酚氧化酶的抑制作用

研究了栎皮酮对甜菜夜蛾Spodopteraexigua 酚氧化酶活力的影响。结果表明: 栎皮酮对该虫的单酚酶和二酚酶活性均表现很强的抑制作用,其I⁵⁰分别为0.079 mmol/L和0.087 mmol/L。其中,栎皮酮对单酚酶活力表达的迟滞时间有明显的延长效应,浓度 为0.079 mmol/L时可使单酚酶活力表达迟滞时间从134s 延长到330s;而当浓度为0.158 mmol/L时,其迟滞时间则延长至440s。以L 多巴为底物时,栎皮酮对二酚酶的抑制作用表现 为典型的竞争型抑制类型,抑制常数K_I为33.16 mmol/L。在研究金属离子对栎皮酮吸收 峰影响实验中发现,Cu²⁺对吸收峰影响最大,可使栎皮酮最大吸收波长从367 nm改变为 435 nm;而加入Mg^2+与Ca²⁺后,其最大吸收峰却无明显的偏移。     

A hydrogel–fiber–hydrogel composite scaffold based on silk fibroin with the dual-delivery of oxygen and quercetin

Supplying sufficient oxygen within the scaffolds is one of the essential hindrances in tissue engineering that can be resolved by oxygen-generating biomaterials (OGBs). Two main issues related to OGBs are controlling oxygenation and reactive oxygen species (ROS). To address these concerns, we developed a composite scaffold entailing three layers (hydrogel-electrospun fibers-hydrogel) with antioxidant and antibacterial properties. The fibers, the middle layer, reinforced the composite structure, enhancing the mechanical strength from 4.27 ± 0.15 to 8.27 ± 0.25 kPa; also, this layer is made of calcium peroxide and silk fibroin (SF) through electrospinning, which enables oxygen delivery. The first and third layers are physical SF hydrogels to control oxygen release, containing quercetin (Q), a nonenzymatic antioxidant. This composite scaffold resulted in almost more than 40 mmHg of oxygen release for at least 13 days, and compared with similar studies is in a high range. Here, Q was used for the first time for an OGB to scavenge the possible ROS. Q delivery not only led to antioxidant activity but also stabilized oxygen release and enhanced cell viability. Based on the given results, this composite scaffold can be introduced as a safe and controllable oxygen supplier, which is promising for tissue engineering applications, particularly for bone.     

无梗五加果化学成分的研究

从无梗五加(Acanthopanax sessiliflorus(Rupr.et Maxim.)Seem.)果70%乙醇提取物中分离鉴定了12个化合物.经波谱鉴定为东莨菪内酯(1),原儿茶酸甲酯(2),槲皮素(3),无梗五加苷B(4),金丝桃苷(5),(-)-pinoresinol-4,4'-di-O-β-D-glucopyranoside(6),chiisanoside(7),22a.hydroxyehiisanoside(8),niduloic acid(9),胡萝卜苷(10),东莨菪苷(11)和无梗五加苷D(12).其中化合物9为新天然产物,化合物1,2,6和11是首次从五加科植物中分离得到,化合物3是首次从五加属植物中分离得到.