Lipid-Lowering Effect of Eriocitrin, the Main Flavonoid in Lemon Fruit, in Rats on a High-Fat and High-Cholesterol Diet

ABSTRACT:  Eriocitrin (eriodictyol 7- O -β-rutinoside) is the main flavonoid in lemon fruit. In this study, eriocitrin was investigated for its lowering effect on serum and hepatic lipids in high-fat and high-cholesterol fed rats. Rats in the control group ( N = 6) were fed a 20% lard and 1% cholesterol diet for 21 d, and rats in the 0.35% eriocitrin group ( N = 6) and 0.70% eriocitrin group ( N = 6) were fed a diet supplemented with eriocitrin 0.35% and 0.70%, respectively. The content of hepatic total cholesterol and triglyceride in the eriocitrin group was no different from that of the control group. The total cholesterol, VLDL+LDL, triglyceride, and phospholipid in the serum of the 0.35% eriocitrin group showed significantly lower concentrations than the control group ( P < 0.05), although there was no difference in the HDL concentrations among the groups. The lowering effect of eriocitrin for serum total cholesterol was thought to be caused by a decrease in VLDL+LDL. The 0.35% eriocitrin group was shown to have a significant increase in excretion of fecal bile acid ( P < 0.05) and a tendency for enhanced hepatic m-RNA levels of LDL receptor in comparison with the control group.     

Antioxidant vs. Prooxidant Properties of the Flavonoid,Kaempferol, in the Presence of Cu(II) Ions: A ROS-Scavenging Activity,Fenton Reaction and DNA Damage Study

Kaempferol is a flavonoid that occurs in tea and in many vegetables and fruits, including broccoli, cabbage, beans, grapes, apples, and strawberries. The efficacy of Kaempferol has been demonstrated in the treatment of breast, esophageal, cervical, ovarian, and liver cancers and leukemia, which very likely arises from its prooxidant properties and the activation of pro-apoptotic pathways. Indeed, this matter has already been the focus of a number of published studies and reviews. The aim of the present study was to elucidate the antioxidant vs. prooxidant properties of flavonoids in the presence of the redox-active metal, copper (II) ion, by means of the Fenton reaction. The specific motivation of this work is that, since an increased level of Cu(II) ions is known to be associated with many disease states such as neurological conditions (Alzheimer’s disease) and cancer, any interaction between these ions and flavonoids might affect the outcome of therapeutic uses of the latter. The structure of the Cu-kaempferol complex in DMSO was investigated by means of low temperature EPR spectroscopy, which confirmed the existence of at least two distinct coordination environments around the copper (II) ion. UV vis-spectra of kaempferol and its Cu(II) complex in DMSO revealed an interaction between the 5-OH (A ring) group and the 4-CO (C ring) group of kaempferol with Cu(II) ions. An ABTS assay confirmed that kaempferol acted as an effective radical scavenger, and that this effect was further enhanced in the form of the Cu(II)-kaempferol complex. Quantitative EPR spin trapping experiments, using DMPO as the spin trap, confirmed suppression of the formation of a mixture of hydroxyl, superoxide, and methyl radicals, in a Fenton reaction system, upon coordination of kaempferol to the redox-active Cu(II) ions, by 80% with respect to the free Cu(II) ions. A viscometric study revealed a better DNA-intercalating ability of the Cu-kaempferol complex than for free kaempferol, essential for conferring anticancer activity of these substances. The results of the viscometric measurements were compared with those from a DNA damage study of Cu-kaempferol complexes in a Fenton reaction system, using gel electrophoresis. At low concentrations of kaempferol (Cu–kaempferol ratios of 1:1 and 1:2), a very weak protective effect on DNA was noted, whereas when kaempferol was present in excess, a significant DNA-protective effect was found. This can be explained if the weakly intercalated kaempferol molecules present at the surface of DNA provide protection against attack by ROS that originate from the Fenton reaction involving intercalated Cu(II)-kaempferol complexes. Following the application of ROS scavengers, L-histidine, DMSO, and SOD, gel electrophoresis confirmed the formation of singlet oxygen, hydroxyl radicals, and superoxide radical anions, respectively. We propose that the prooxidant properties of Cu-kaempferol complexes may provide anticancer activity of these substances. When present in excess, kaempferol displays antioxidant properties under Cu-Fenton conditions. This suggests that kaempferol might prove a suitable candidate for the prevention or treatment of oxidative stress related medical conditions that involve a disturbed metabolism of redox metals such as copper, for example, Menkes disease, and neurological disorders, including Alzheimer’s disease. For the potential use of kaempferol in clinical practice, it will be necessary to optimize the dose size and critical age of the patient so that this flavonoid may be beneficial as a preventive drug against cancer and neurological disorders.     

Inhibition of lipid peroxidation in UVA‐treated skin fibroblasts by luteolin and its glucosides

Ultraviolet A (UVA) radiation causes oxidative damage to human skin cells. This damage may be reduced or prevented using plant compounds as photoprotectants. To investigate the relationship between chemical structure and UVA‐protective activity, three structurally related flavonoids, namely luteolin, luteolin‐7‐O‐glucoside (both present in artichoke) and luteolin‐4'‐O‐glucoside (present in wild carrot), were studied. Human skin fibroblasts exposed to UVA (250 and 500 kJ/m²) were treated with each flavonoid (30 µM) for 18 h prior to irradiation. The extent of lipid peroxidation in the cellular extracts was assessed as lipid peroxides and malondialdehyde (MDA). Luteolin and luteolin‐7‐O‐glucoside both prevented a significant increase in lipid peroxides at 250 kJ/m², but at 500 kJ/m² their effectiveness was clearly attenuated. Contrastingly, luteolin‐4'‐O‐glucoside was pro‐oxidant at both radiation doses. Measurements of MDA levels highlighted that luteolin was clearly more effective than the two glucosides at both 250 and 500 kJ/m². Overall, these results show clear differences between the three flavonoids and suggest that the B ring 3',4'‐dihydroxy group, lacking in luteolin‐4'‐O‐glucoside, may be particularly important. Flavonoid: transition metal ion chelation studies confirmed the influence of the 3',4'‐dihydroxy group, which is also relevant to the quenching of singlet oxygen. These features as well as the greater lipophilic nature of luteolin together explain the superior activity of this flavonoid which may be potentially useful as a supplement in photoprotective skin preparations.     

荧光法研究3种黄酮化合物与牛血清白蛋白的结合作用

运用荧光光谱法研究了生理酸度条件下（pH=7.4）3种黄酮化合物白杨素、芹菜素和桑色素与牛血清白蛋白（BSA）的结合作用。结果表明,3种黄酮化合物均能与BSA形成基态复合物导致BSA内源荧光猝灭,猝灭机理为静态猝灭。结合常数K（芹菜素）〉K（白杨素）〉K（桑色素）,结合位点数近似等于1,白杨素与BSA之间以疏水作用为主,而芹菜素、桑色素与BSA之间的作用力主要是氢键和范德华力。黄酮分子结构中羟基位置及个数影响其与BSA间的结合作用,C4＇-OH对结合有促进作用,而C3-OH的取代则导致作用力减弱。由Frster非辐射能量转移理论,计算出3种黄酮化合物在蛋白质中的结合位置与212位色氨酸残基间的距离分别为2.44 nm（白杨素）、3.34 nm（芹菜素）和3.31 nm（桑色素）。     

γ-氨基丁酸受体同源模建及与黄酮类化合物的分子对接

为研究更有效的γ-氨基丁酸受体激动剂,以海兔烟碱乙酰胆碱结合蛋白(PDB登记号2XYS,0.194 nm)作为模板,运用同源模建的方法构建人γ-氨基丁酸A型受体模型,并利用拉氏图和分子动力学分析验证其模型的合理性.将41个黄酮类化合物与模建的人γ-氨基丁酸A型受体进行对接研究,对接打分与实测活性值相吻合.黄酮类化合物与人γ-氨基丁酸A型受体对接结果显示,黄酮类化合物的母环分别与190位酪氨酸和140位酪氨酸形成共轭,降低体系能量并使体系稳定,验证了模型的合理性.此外,3'位对黄酮类化合物活性的影响至关重要,尤其引入硝基时活性明显提高.38号化合物的对接打分最高,也说明相应的增加取代基个数有利于提高该类化合物活性.     

Green and gold kiwifruit peel ethanol extracts potentiate pentobarbital-induced sleep in mice via a GABAergic mechanism

Kiwifruit is one of the most popular fruits worldwide, and it has various biological properties, including antioxidant, anti-allergic, and cardiovascular protective effects. The peel of kiwifruit, which is a by-product of processing, is a good source of flavonoids; however, its bioactivity has not been widely investigated. In this study, we evaluated the hypnotic effects of green (GRPE, Actinidia deliciosa) and gold (GOPE, Actinidia chinensis) kiwifruit peel ethanol extracts and their solvent fractions, and the possible underlying mechanisms. Oral GRPE and GOPE administration (125–1000 mg/kg) produced a dose-dependent decrease in sleep latency and an increase in sleep duration in pentobarbital-treated mice. Among three different solvent fractions of GRPE and GOPE, ethyl acetate (EA) fractions had the greatest effect on sleep duration at 250 mg/kg. The total flavonoid contents of solvent fractions were proportional to sleep duration. Like diazepam (a GABA_A–benzodiazepine (BZD) receptor agonist), the hypnotic effects of GRPE, GOPE, and their EA fractions were fully inhibited by flumazenil (a GABA_A–BZD receptor antagonist). These results suggest that potentiation effects of GRPE and GOPE on pentobarbital-induced sleep in mice may be modulated by a GABAergic mechanism.     

Impact of Rutin and Other Phenolic Substances on the Digestibility of Buckwheat Grain Metabolites

Tartary buckwheat (Fagopyrum tataricum Gaertn.) is grown in eastern and central Asia (the Himalayan regions of China, Nepal, Bhutan and India) and in central and eastern Europe (Luxemburg, Germany, Slovenia and Bosnia and Herzegovina). It is known for its high concentration of rutin and other phenolic metabolites. Besides the grain, the other aboveground parts of Tartary buckwheat contain rutin as well. After the mixing of the milled buckwheat products with water, the flavonoid quercetin is obtained in the flour–water mixture, a result of rutin degradation by rutinosidase. Heating by hot water or steam inactivates the rutin-degrading enzymes in buckwheat flour and dough. The low buckwheat protein digestibility is due to the high content of phenolic substances. Phenolic compounds have low absorption after food intake, so, after ingestion, they remain for some time in the gastrointestinal tract. They can act in an inhibitory manner on enzymes, degrading proteins and other food constituents. In common and Tartary buckwheat, the rutin and quercetin complexation with protein and starch molecules has an impact on the in vitro digestibility and the appearance of resistant starch and slowly digestible proteins. Slowly digestible starch and proteins are important for the functional and health-promoting properties of buckwheat products.     

菊花中黄酮类物质提取方法的研究

就水提法、醇提法、超声波法对菊花中黄酮类化合物的提取效果进行了比较,并使用正交实验确定了最佳提取条件。实验结果表明,菊花中总黄酮类物质的醇提法最佳提取条件为C3B3A1,即用1倍量80%的乙醇连续回流提取3次(每次2h);超声波法的最佳提取条件为:将样品置于60倍样品重的80%乙醇中浸泡24h,超声波提取15min。     

红树莓叶片中黄酮类物质提取及抗氧化性的研究

以小浆果果树红树毒叶片为实验材料，利用分光光度法测定其总黄酮含量，并采用烘箱贮存法研究了不同添加量红树毒叶片提取物粗黄酮在猪油中的抗氧化性。结果表明：鲜样中红树毒叶片总黄酮含量是278．73mg／100g，干样中是533．71mg／100g；红树毒叶片提取物粗黄酮对猪油有一定的抗氧化作用，并随添加量的增加而增强；增效剂以(柠檬酸)对红树毒叶片提取物粗黄酮无增效作用，而Vc具有一定的增效作用。抗氧化活性顺序为：0．02％槲皮素＞0．02％PG＞0．02％BHT＞0．4％粗黄酮＞0．05％粗黄酮 0．05％Vc＞0．2％粗黄酮＞0.1％粗黄酮＞0．05％粗黄酮＞0．02％粗黄酮＞0．05％粗黄酮 0．05％CA＞对照。