Effect of rutin and its copper complex on superoxide formation and lipid peroxidation in rat liver microsomes

The antioxidant Rutin counteracts the pathological impact of α-synuclein on the enteric nervous system in vitro

Motoric disturbances in Parkinson's disease (PD) derive from the loss of dopaminergic neurons in the substantia nigra. Intestinal dysfunctions often appear long before manifestation of neuronal symptoms, suggesting a strong correlation between gut and brain in PD. Oxidative stress is a key player in neurodegeneration causing neuronal cell death. Using natural antioxidative flavonoids like Rutin, might provide intervening strategies to improve PD pathogenesis. To explore the potential effects of micro (mRutin) compared to nano Rutin (nRutin) upon the brain and the gut during PD, its neuroprotective effects were assessed using an in vitro PD model. Our results demonstrated that Rutin inhibited the neurotoxicity induced by A53T α-synuclein (Syn) administration by decreasing oxidized lipids and increasing cell viability in both, mesencephalic and enteric cells. For enteric cells, neurite outgrowth, number of synaptic vesicles, and tyrosine hydroxylase positive cells were significantly reduced when treated with Syn. This could be reversed by the addition of Rutin. nRutin revealed a more pronounced result in all experiments. In conclusion, our study shows that Rutin, especially the nanocrystals, are promising natural compounds to protect neurons from cell death and oxidative stress during PD. Early intake of Rutin may provide a realizable option to prevent or slow PD pathogenesis.

Cu(ii) phenanthroline–phenazine complexes dysregulate mitochondrial function and stimulate apoptosis

Herein we report the central role of the mitochondria in the cytotoxicity of four developmental cytotoxic copper(ii) complexes [Cu(phen)₂]²⁺, [Cu(DPQ)(Phen)]²⁺, [Cu(DPPZ)(Phen)]²⁺and [Cu(DPPN)(Phen)]²⁺superior to cisplatin and independent of resistance in a range of cells.

Anti-genotoxic effect of naringin against bleomycin-induced genomic damage in human lymphocytes in vitro

Naringin is a flavonoid found in grapefruit and other citrus fruits that shows antioxidant activity. The aim of the present study was to determine the anti-genotoxic and protective effects of naringin on the chemotherapeutic/radiomimetic agent bleomycin (BLM) in human blood lymphocyte cultures in vitro using micronucleus test and chromosomal aberrations (CA) assay. We tested the three doses of naringin (1, 2, 3 µg/mL) and a single dose of BLM (20 µg/mL). BLM significantly increased the total CAs and micronucleus frequency at a concentration of 20 µg/mL. Naringin did not show any toxicity in doses of 1, 2, and 3 µg/mL. Combined treatments of BLM and naringin (2 and 3 µg/mL) significantly reduced micronucleus formation. Naringin dose-dependently decreased the total chromosome aberrations frequency induced by BLM. These results indicate that naringin could prevent BLM (20 µg/mL)-induced genotoxicity.

Flavonoids protecting food and beverages against light

Flavonoids, which are ubiquitously present in the plant kingdom, preserve food and beverages at the parts per million level with minor perturbation of sensory impressions. Additionally, they are safe and possibly contribute positive health effects. Flavonoids should be further exploited for the protection of food and beverages against light-induced quality deterioration through: (1) direct absorption of photons as inner filters protecting sensitive food components; (2) deactivation of (triplet-)excited states of sensitisers like chlorophyll and riboflavin; (3) quenching of singlet oxygen from type II photosensitisation; and (iv) scavenging of radicals formed as reaction intermediates in type I photosensitisation. For absorption of light, combinations of flavonoids, as found in natural co-pigmentation, facilitate dissipation of photon energy to heat thus averting photodegradation. For protection against singlet oxygen and triplet sensitisers, chemical quenching gradually decreases efficiency hence the pathway to physical quenching should be optimised through product formulation. The feasibility of these protection strategies is further supported by kinetic data that are becoming available, allowing for calculation of threshold levels of flavonoids to prevent beer and dairy products from going off. On the other hand, increasing understanding of the interplay between light and matrix physicochemistry, for example the effect of aprotic microenvironments on phototautomerisation of compounds like quercetin, opens up for engineering better light-to-heat converting channels in processed food to eventually prevent quality loss.

Ocimum gratissimum is Effective in Prevention against Liver Fibrosis in Vivo and in Vitro

Ocimum gratissimum is a traditional herb commonly found in tropical regions, which prevents free radical damage and protects the liver from oxidative stress. In this study, we tested in vivo and in vitro the effectiveness of O. gratissimum extracts (OGEs) in anti-hepatic fibrosis in rats. Male Wistar rats were administered with carbon tetrachloride (CCl4) by intraperitoneal injection and varying amounts of oral injection of OGE doses (0–40 mg/kg body weight) for 8 weeks. Our experiments showed that OGE significantly reduced liver damage, including steatosis and fibrosis, in a dose-dependent manner, as well as significantly decreased the elevation in plasma aspartate aminotransferase (AST) and alanine aminotransferase (ALT). It also inhibited the formation of lipid peroxidative products during CCl4 treatment. Moreover, OGE-inhibited CCl4-induced liver collagen accumulation and promoted the expression of catalase, an anti-oxidative enzyme. The inhibition of fibrosis factors α-SMA expression was also observed. In primary cultures, OGE significantly inhibited the serum-induced activation of hepatic stellate cells (HSCs), and the expression of α-SMA and collagen α (I). These data suggest that O. gratissimum possesses anti-hepatic fibrosis properties via its anti-oxidative components.

Synthesis, spectral and thermal studies of new rutin vanadyl complexes

Complexes between oxovanadium (IV) cation and flavonoid derivatives were developed recently in order to increase the intestinal absorption and to reduce the toxicity of vanadium compounds. For these reasons, is interesting to investigate the complexation process between flavonoid rutin (Rut) and vanadyl cation in order to isolate new complexes. Two new complexes [VO(Rut)(H2O)2](SO4)0.5 x 2 H2O and [VO(Rut)2] x 4 H2O have been obtained and characterized by elemental and thermal analyses and several spectroscopic techniques (ESI-MS, IR, UV-Vis, fluorescence). The studies concerning complex formation between vanadyl and rutin (Rut) performed in different solutions show the formation of mononuclear complexes with 1:1 and 1:2 metal to ligand stoichiometry.

Inhibition of iron induced lipid peroxidation and antioxidant activity of Indian spices and Acacia in vitro

The spices used in the Indian foods such as Star anise (Illicium verum), Bay leaves (Cinnamomum zeylanicum) and Cobra's saffron (Mesua ferrea), and Acacia (Acacia catechu), which have medicinal value, were used as test samples, to find their effect on in vitro lipid peroxidation (LPO). Rat liver post mitochondrial supernatant (PMS) in Tris HCl buffer, pH 7.4 was incubated for 0 and 1 h, with various test extracts in three different oxidant systems. The results show that addition of test samples to FeCl(3) medium at 0 h significantly stop the initiation of the LPO. However, the propagation phase of LPO was inhibited by Cobra's saffron and Acacia and not by Star anise and Bay leaves. The test samples also showed strong reducing power and superoxide radical scavenging activity. Cobra's saffron and Acacia showed the highest antioxidant activity, probably due to the higher polyphenol content as compared to other test samples.

Structure-property studies on the antioxidant activity of flavonoids present in diet

The screening of natural flavonoids for their bioactivity as antioxidants is usually carried out by determinination of their profile as chain-breaking antioxidants, by the evaluation of their direct free radical-scavenging activity as hydrogen- or electron-donating compounds. Since this may not be the only mechanism underlying the antioxidant activity it is important to check the ability of these compounds to act as chelators of transition metal ions. Accordingly, in the present study the acidity constants of catechin and taxifolin, as well as the formation constants of the corresponding copper (II) complexes, were investigated by potentiometry and/or spectrophotometry. Moreover, a detailed quantitative examination of the coordination species formed is presented. In addition, the partition coefficients of both catechin and taxifolin in a biomimetic system (micelles) were determined, since these properties may also contribute to the antioxidant behavior of this type of compound. The log P values determined depend on the electrostatic interactions of the compounds with the differently charged micelles (the highest values were obtained for zwitterionic and cationic micelles). The prooxidant behavior of the compounds was assessed through the oxidation of 2'-deoxyguanosine, induced by a Fenton reaction, catalyzed by copper. The data obtained reveal that the flavonoids under study did not present prooxidant activity, in this particular system. The results obtained are evidence of a clear difference among the pKa, the complexation properties, and the lipophilicity of the flavonoids studied, which can partially explain their distinct antioxidant activity. The most stable geometries of the free compounds were determined by theoretical (ab initio) methods, in order to properly account for the electron correlation effects which occur in these systems, thus allowing a better interpretation of the experimental data.

Experimental evidence that flavonoid metal complexes may act as mimics of superoxide dismutase

Radical scavenging activities of flavonoids rutin, taxifolin, (-)-epicatechin, luteolin, and their complexes with transition metal (Fe2+, Fe3+, and Cu2+) towards superoxide were determined using illumination of riboflavin as source and NBT as detector of O*2-. The scavenger potencies of flavonoid metal complexes were significantly higher than those of the parent flavonoids. To elucidate the mechanism of this phenomenon, the rates of superoxide-dependent oxidation of flavonoids and their metal complexes in photochemical system with riboflavin were examined. It was found for the first time that flavonoids bound to metal ions were much less subjected to oxidation compared with those of free compounds. The findings directly demonstrate superoxide scavenging activity of metal ions in complexes with flavonoids and support earlier suggestions that flavonoid metal complexes may exhibit superoxide dismuting activity.

The role of ascorbic acid on the redox status and the concentration of malondialdehyde in streptozotocin-induced diabetic rats

We investigated the role of ascorbic acid on the redox status in streptozotocin-induced diabetic rats. In the plasma of diabetic rats, the ratio of reduced/total ascorbic acid was significantly decreased as compared with normal control. Ascorbic acid supplementation increased the reduced and total ascorbic acid contents as compared with diabetic control. In the rutin-treatment group, reduced and total contents of ascorbic acid were significantly decreased, however, the ratio of reduced/total contents of ascorbic acid had no difference as compared with diabetic rats. In the insulin-treatment group, this ratio is not significantly different as compared with diabetic control. However, in the insulin plus ascorbic acid treatment group, reduced form and the ratio of reduced/total ascorbic acid were significantly increased as compared with diabetic control. In addition, we measured the contents of malondialdehyde (MDA) in the plasma of diabetic rats. The contents of MDA was increased as compared with normal control, however, in insulin-treatment group, the contents of MDA was decreased as compared with diabetic rats. Ascorbic acid had no effects on the increases of MDA in diabetic rats. In conclusion, plasma ascorbic acid level and its reduced/total ratio reflects the status of the oxidative stress in the diabetic rats. Supplement of ascorbic acid did not correct the ratio of the reduced/ total ascorbic acid. However, supplement of insulin and ascorbic acid corrected the ratio of reduced/total ascorbic acid.

Dietary flavonoid iron complexes as cytoprotective superoxide radical scavengers

Superoxide radicals have been implicated in the pathogenesis of ischemia/reperfusion, aging, and inflammatory diseases. In the present work, we have shown that the Fe(3+) complexes of flavonoids (polyphenols) were much more effective than the uncomplexed flavonoids in protecting isolated rat hepatocytes against hypoxia-reoxygenation injury. The 2:1 flavonoid-metal complexes of Cu(2+), Fe(2+), or Fe(3+) were more effective than the parent compounds in scavenging superoxide radicals generated by xanthine oxidase/hypoxanthine (an enzymatic superoxide-generating system). The 2:1 [flavonoid:Fe(3+)] complexes but not the [deferoxamine:Fe(3+)] complex readily scavenged superoxide radicals. These results suggest that the initial step in superoxide radical scavenging (SRS) activity involves a redox-active flavonoid:Fe(3+) complex. Flavonoid:Fe(3+) complexes should, therefore, be tested as a therapy for the treatment of ischemia/reperfusion injury.

Combination of vitamin C and rutin on neuropathy and lung damage of diabetes mellitus rats

We investigated the role of vitamin C or rutin on neuropathy and lung damage of diabetic mellitus (DM) rats. Norepinephrine content was significantly decreased in sciatic nerves'of DM rats compared with non-DM controls but vitamin C had no effect on decreases of norepinephrine. 2,4-dinitrophenylhydrazine (DNPH) incorporation, which is biomarker of protein oxidation, was increased in sciatic nerve of DM rats as compared with normal control. However, vitamin C had no effects on increases of DNPH incorporation. We measured the content of conjugated dienes (CD) as a biomarker of lipid oxidation in sciatic nerve. CD was increased in DM as compared with normal control. Vitamin C or rutin had no effects on increases of CD. However, Rutin plus vitamin C significantly decreased the content of CD as compared with DM rats. In lung of DM rats, DNPH incorporation or CD was increased as compared with normal control. Vitamin C or Rutin had no effects on increases of CD. However, Rutin plus vitamin C significantly decreased the content of DNPH incorporation or CD in lung tissue. Vitamin C caused marked pathological changes such as the increases of parenchyma and the thickening of alveolar septa in the lung of DM. Rutin had protective effects on the pathological changes in the lung of DM rats. In conclusion, Vitamin C had no effects on oxidative parameter, such as DNPH incorporation or CD, and on the decreases of norepinephrine content in DM rats. Vitamin C caused the marked pathological changes in the lung of DM rats but rutin had protective effects against the pathological changes.

Iron complexes of deferiprone and dietary plant catechols as cytoprotective superoxide radical scavengers(1)

Superoxide radicals have been implicated in the pathogenesis of aging, cataract, ischemia-reperfusion, cancer and inflammatory diseases. In the present work, we found that deferiprone (L1), an iron-chelating drug, and dietary dihydroxycinnamic acids (catechols) were much more effective at protecting isolated rat hepatocytes against hypoxia-reoxygenation injury if complexed with Fe(3+). Furthermore, the 2:1 catechol-metal complexes with Cu(2+), Fe(2+), and Fe(3+) were also more effective than uncomplexed catechols in scavenging superoxide radicals generated enzymically (xanthine oxidase/hypoxanthine). The 2:1 deferiprone:Fe(3+) complex was less effective at scavenging enzymically generated superoxide radicals even though it was effective at preventing hepatocyte hypoxia-reoxygenation injury. On the other hand, the 1:1 deferoxamine:Fe(3+) complex, another iron-chelating drug, did not prevent hepatocyte hypoxia-reoxygenation injury and did not scavenge enzymically generated superoxide radicals. Furthermore, hepatocytes readily reduced the 2:1 deferiprone:Fe(3+) complex but not the deferoxamine:Fe(3+) complex. These results suggest that the initial step in superoxide radical scavenging (SRS) activity is the formation of a redox complex between Fe(3+) and deferiprone or catechols. The [deferiprone:Fe(3+)] complex was more cytoprotective than would be expected from its SRS activity. This suggests that [deferiprone:Fe(3+)] complex is reduced by a ferrireductase present on the hepatocyte membrane to form [deferiprone:Fe(2+)] complex, which then scavenges superoxide radicals. Therefore, the clinically used deferiprone (L1) may have therapeutic advantages over deferoxamine in having a double role therapeutically: (a) it chelates iron to alleviate iron overload pathology, and (b) the readily formed iron complex protects hepatocytes from superoxide radical-mediated hypoxia-reoxygenation injury.

Influence of metal ions on flavonoid protection against asbestos-induced cell injury

Influence of metal ions (Fe2+, Fe3+, Cu2+, Zn2+) on the protective effect of rutin, dihydroquercetin, and green tea epicatechins against in vitro asbestos-induced cell injury was studied. Metals have been found to increase the capacity of rutin and dihydroquercetin to protect peritoneal macrophages against chrysotile asbestos-induced injury. The data presented here show that this effect is due to the formation of flavonoid metal complexes, which turned out to be more effective radical scavengers than uncomplexed flavonoids. At the same time epicatechins and their metal complexes have similar antiradical properties and protective capacities against the asbestos induced injury of macrophages. Metal complexes of all flavonoids were found to be considerably more potent than parent flavonoids in protecting red blood cells against asbestos-induced injury. It was also found that the metal complexes of all flavonoids were absorbed by chrysotile asbestos fibers considerably better than uncomplexed compounds and probably for this reason flavonoid metal complexes have better protective properties against asbestos induced hemolysis. Thus, the results of the present study show that flavonoid metal complexes may be effective therapy for the inflammatory response associated with the inhalation of asbestos fiber. The advantage of their application could be the strong increase in ROS scavenging by flavonoids and finally a better cell protection under the conditions of cellular oxidative stress.

Enhancement of antioxidant and anti-inflammatory activities of bioflavonoid rutin by complexation with transition metals

The antioxidant and anti-inflammatory activities of two transition metal complexes of bioflavonoid rutin, Fe(rut)Cl(3) and Cu(rut)Cl(2), were studied. It was found that Cu(rut)Cl(2) was a highly efficient in vitro and ex vivo free radical scavenger that sharply decreased (by 2-30 times compared to the parent rutin): oxygen radical production by xanthine oxidase, rat liver microsomes, and rat peritoneal macrophages; the formation of thiobarbituric acid-reactive products in microsomal lipid peroxidation; and the generation of oxygen radicals by broncho-alveolar cells from bleomycin-treated rats. The copper-rutin complex was also a superior inhibitor of inflammatory and fibrotic processes (characterized by such parameters as macrophage/neutrophil ratio, wet lung weight, total protein content, and hydroxyproline concentration) in the bleomycin-treated rats. The antioxidant activity of Fe(rut)Cl(3) was much lower and in some cases approached that of rutin. Fe(rut)Cl(3) also stimulated to some degree spontaneous oxygen radical production by macrophages. We suggested that the superior antioxidant and anti-inflammatory activity of the copper-rutin complex is a consequence of its acquiring the additional superoxide-dismuting copper center. The inhibitory activity of Fe(rut)Cl(3) was lower, probably due to the partial reduction into Fe(rut)Cl(2) in the presence of biological reductants; however, similarly to the copper-rutin complex, this complex efficiently suppressed lung edema.