Antioxidant activity of 5-alkoxymethyl-6-chromanols

Abstract

The 5-alkoxymethyl-2,2,7,8-tetramethyl-6-chromanols (II) are excellent antioxidants against autoxidising safflower oil (ASO), although not as good as 2,2,5,7,8-pentamethyl-6-chromanol (I), the model compound of -tocopherol. The aim of this work was to determine whether the rate of reaction of (II) with the radicals diphenylpicrylhydrazyl (DPP^·) and galvinoxyl (ArO^·) was directly proportional to their antioxidant activity against ASO. Compounds (II) reacted faster with DPP^·. than with ArO^·. but, in each case, slower than compound (I). The rates of reaction of I and II with both radicals followed the order I > II (R = H) > II (R = CH₃) > II (R = other alkyls) and were directly proportional to their antioxidant activity against ASO.     

Antioxidant activity of 3-methyl-1-phenyl-2-pyrazolin-5-one

Summary

The antioxidant activity of an anti-ischemic agent, 3-methyl-1-phenyl-2-pyrazolin-5-one (MCI-186), was examined. The pKa value of MCI-186 is 7.0 and the rate of oxidation of MCI-186 initiated with an azo compound increased with increasing pH, suggesting that the anionic form of MCI-186 is much more reactive than the non-ionic form. The major products were 3-methyl-1-phenyl-2-pyrazolin-4,5-dione (4,5-dione) and 2-oxo-3-(phenylhydrazono)-butanoic acid (OPB). Hydrolysis of 4,5-dione gave OPB. The minor intermediate product was 4-hydroxy-4-(3-methyl-1-phenyl-1H-pyrazolin-5-on-4-yl)-3-methyl-1-phenyl-1H-pyrazolin-5-one (BPOH). The nucleophilic attack of the anionic form of MCI-186 to 4,5-dione is likely to give BPOH. MCI-186 (50 μM) inhibited the aerobic oxidation at 37°C of 5.2 mM unilamellar soybean phosphatidylcholine (PC) liposomal membranes, initiated with a water-soluble initiator, as efficientlyas did ascorbate (100 μM). MCI-186 (50 μM) also inhibited the oxidation of the same PC liposomal membranes, this time initiated with a lipid-soluble initiator, almost as efficiently as did α-tocopherol (2 μM). Furthermore, the combination of MCI-186 with ascorbate or α-tocopherol showed almost complete inhibition of PC oxidation induced by both initiators. These data suggest that MCI-186 may work as a good antioxidant in cellular systems as well as in cell-free systems.     

Antioxidant function of phenethyl-5-bromo-pyridyl thiourea compounds with potent anti-HIV activity

In a systematic search for novel dual function antioxidants with potent anti-HIV activity, we evaluated 9 rationally designed non-nucleoside inhibitors (NNI) of HIV-1 RT for antioxidant and anti-HIV activities. Our lead phenethyl-5-bromopyridyl thiourea (PEPT) compounds, N-[2-(2-methoxyphenylethyl)]-N'-[2-(5-bromopyridyl)]-thioure a (2) and N-[2-(2-chlorophenylethyl)]-N'-[2-(5-bromopyridyl)]-thiourea (9), inhibited the oxidation of ABTS to ABTS*+ by metmyoglobin in the presence of hydrogen peroxide with EC50 values of 79 and 75 microM, respectively. Both compounds effectively inhibited the oxidation-induced green fluorescence emission from the free radical-sensitive indicator dye 2',7'-dichlorodihydrofluorescein diacetate in CEM human T-cells and Nalm-6 human B-cells exposed to hydrogen peroxide. To our knowledge, compounds 2 and 9 are the first NNI of HIV-1 RT with potent anti-oxidant activity. Furthermore, the activity center was defined as the sulfhydryl group since alkylated PEPT derivatives were inactive. The presence of a free thiourea group was also essential for the anti-HIV activity of the PEPT compounds.     

Antioxidant activity of carotenoids

Carotenoids are pigments which play a major role in the protection of plants against photooxidative processes. They are efficient antioxidants scavenging singlet molecular oxygen and peroxyl radicals. In the human organism, carotenoids are part of the antioxidant defense system. They interact synergistically with other antioxidants; mixtures of carotenoids are more effective than single compounds. According to their structure most carotenoids exhibit absorption maxima at around 450 nm. Filtering of blue light has been proposed as a mechanism protecting the macula lutea against photooxidative damage. There is increasing evidence from human studies that carotenoids protect the skin against photooxidative damage.     

Antioxidant activity of synthetic cytokinin analogues: 6-alkynyl- and 6-alkenylpurines as novel 15-Lipoxygenase inhibitors

Synthetic cytokinin analogues as well as the well known CKs 6-benzylaminopurine (BAP), kinetin and trans-zeatin were examined for antioxidant activity. The compounds were tested as potential diphenylpicrylhydrazyl (DPPH) scavengers and as inhibitors of 15-lipoxygenase (15-LO). The natural plant hormones were essentially inactive in both assays, but several synthetic analogues have a profound inhibiting effect on 15-lipoxygenase from soybeans. The same compounds were only weak DPPH scavengers and they may therefore be regarded as so-called non antioxidant inhibitors of 15-LO.     

Antioxidant activity of brahma rasayana

Free oxygen radical scavenging activity of brahma rasayana (BR) was studied by in vitro and in vivo models. Addition of aqueous extract of BR was found to scavenge the lipid peroxides already present in rat liver homogenate (IC50 700 micrograms/ml) and inhibit the lipid peroxide generated by Fe(2+)-ascorbate (IC50 2600 micrograms/ml) and Fe(3+)-ADP-ascorbate system (IC50 1200 micrograms/ml). BR was found to scavenge the hydroxyl radical generated by Fenton reaction (IC50 7400 micrograms/ml) and superoxide generated by photoreduction of riboflavin (IC50 180 micrograms/ml). BR was also found to inhibit the nitric oxide radical generated in vitro from sodium nitroprusside (IC50 5.5 micrograms/ml). Oral administration of BR (50 mg/dose/animal) was found to inhibit the PMA induced superoxide generation in mice peritoneal macrophages. Oral administration of BR; 10 and 50 mg/dose/animal was also found to inhibit the nitrite production in peritoneal macrophages and percentage inhibition was 25.2% and 37.8% respectively. These results indicate significant antioxidant activity of BR in vitro and in vivo.     

Antioxidant activity of different dihydropyridines

Lacidipine, a dihydropyridine-based calcium antagonist (DHP), has already been demonstrated to possess antioxidant activity and to reduce the intracellular production of reactive oxygen species (ROS). To verify if this effect is a peculiarity of this molecule, or belongs to other DHPs, the activity of lacidipine was compared with those of amlodipine, lercanidipine, nimodipine, and nifedipine. The DHPs were incorporated in bovine aortic endothelial cells (BAECs). Cu(2+)-oxidized LDL (ox-LDL, 5 microM) was incubated with BAECs for 5 min. 2',7'-Dichlorofluorescein (DCF) as expression of intracellular ROS production was measured by flow cytometry. Ox-LDL induced a strong increase in intracellular ROS formation (p<0.001) that was significantly reduced only with lacidipine and lercanidipine (p from <0.05 to <0.01); the effect of lacidipine, however, resulted in being much more evident than lercanidipine (p<0.01); amlodipine, nimodopine, and nifedipine had no effect on ROS formation. The lowest IC50s, i.e. the concentrations determining the 50% reduction of ROS, were obtained with lacidipine (p<0.01). The inhibitory effect of lacidipine on ox-LDL-induced ROS production in endothelial cells is a peculiarity of this molecule through its antioxidant activity.     

硫酸化分级香菇多糖抗氧化活性研究

提取香菇子实体多糖,用浓硫酸法进行结构修饰,经不同分子量超滤膜超滤分离得到6种不同组份的硫酸化香菇多糖,检测这6种组份抗氧化活性。结果表明,硫酸化香菇多糖具有抗氧化活性,在1-10mg/mL的浓度范围内呈量效关系,且不同分子量组份活性有差异。     

Nse5/6 is a negative regulator of the ATPase activity of the Smc5/6 complex

The multi-component Smc5/6 complex plays a critical role in the resolution of recombination intermediates formed during mitosis and meiosis, and in the cellular response to replication stress. Using recombinant proteins, we have reconstituted a series of defined Saccharomyces cerevisiae Smc5/6 complexes, visualised them by negative stain electron microscopy, and tested their ability to function as an ATPase. We find that only the six protein ‘holo-complex’ is capable of turning over ATP and that its activity is significantly increased by the addition of double-stranded DNA to reaction mixes. Furthermore, stimulation is wholly dependent on functional ATP-binding pockets in both Smc5 and Smc6. Importantly, we demonstrate that budding yeast Nse5/6 acts as a negative regulator of Smc5/6 ATPase activity, binding to the head-end of the complex to suppress turnover, irrespective of the DNA-bound status of the complex.     

Antioxidant activity of vegetable oils with different omega-6/omega-3 fatty acids ratio

The antioxidant activity and the oxidative stability of flax, sesame, silybum oils and seed blend oils with different ω-6/ω-3 fatty acid ratios have been investigated. The antioxidant content (AO) in crude oils and their reactivity towards peroxyl radicals were studied using the kinetic method based on oil addition to the model reaction of cumene oxidation. There were correlations between the ratio polyunsaturated fatty acids (PUFA)/ω-9 and thermal stability (50°C); between the effect of γ-tocopherol content and oil resistance to oxidative changes during long-term storage at (10 ± 2)°C.     

Biodegradation of diesel fuel by a microbial consortium in the presence of 1-alkoxymethyl-2-methyl-5-hydroxypyridinium chloride homologues

Fast development of ionic liquids as gaining more and more attention valuable chemicals will undoubtedly lead to environmental pollution. New formulations and application of ionic liquids may result in contamination in the presence of hydrophobic compounds, such as petroleum mixtures. We hypothesize that in the presence of diesel fuel low-water-soluble ionic liquids may become more toxic to hydrocarbon-degrading microorganisms. In this study the influence of 1-alkoxymethyl-2-methyl-5-hydroxypyridinium chloride homologues (side-chain length from C₃ to C₁₈) on biodegradation of diesel fuel by a bacterial consortium was investigated. Whereas test performed for the consortium cultivated on disodium succinate showed that toxicity of the investigated ionic liquids decreased with increase in side-chain length, only higher homologues (C₈–C₁₈) caused a decrease in diesel fuel biodegradation. As a result of exposure to toxic compounds also modification in cell surface hydrophobicity was observed (MATH). Disulphine blue active substances method was employed to determine partitioning index of ionic liquids between water and diesel fuel phase, which varied from 1.1 to 51% for C₃ and C₁₈ homologues, respectively. We conclude that in the presence of hydrocarbons acting as a solvent, the increased bioavailability of hydrophobic homologues is responsible for the decrease in biodegradation efficiency of diesel fuel.     

Antioxidant activity of new ruthenium compounds

Many biological properties have been attributed to ruthenium complexes including anti-tumor activity and the attenuation of reperfusion damage and infarct size. In this work, we characterize the antioxidant activity of trans-[RuCl2(nic)4] where nic is 3-pyridinecarboxylic acid and trans-[RuCl2(i-nic)4] where i-nic is 4-pyridinecarboxylic acid by (i) evaluation of total antioxidant potential (TRAP); (ii) prevention of DNA damage induced by hydrogen peroxide using the alkaline comet assay; and (iii) the prevention of lipid peroxidation and cell death induced by iron in liver slices. Our results suggest that nic has stronger antioxidant potential when compared to the i-nic. Higher doses (above 200 microM) of these compounds gave genotoxic effects, but the antioxidant potential could be obtained with the use lower doses (0.1-10 microM).     

Antioxidant activity of Arthritin--a polyherbal formulation

In complete freund's adjuvant induced arthritis in male albino rats, a significant increase in serum lipid peroxidase besides increase in paw swelling and a significant decrease in superoxide dismutase, glutathione peroxidase and total reduced glutathione levels were observed. Arthritin produced a marked reversal of these enzyme levels, besides a significant reduction in paw swelling. The results suggest that, the polyherbal formulation 'Arthritin' exerts its effects by modulating lipid peroxidation and enhancing anti-oxidant and detoxifying enzyme systems.     

Antioxidant activity of selected Indian spices

Spices and vegetables possess antioxidant activity that can be applied for preservation of lipids and reduce lipid peroxidation in biological systems. The potential antioxidant activities of selected spices extracts (water and alcohol 1:1) were investigated on enzymatic lipid peroxidation. Water and alcoholic extract (1:1) of commonly used spices (garlic, ginger, onion, mint, cloves, cinnamon and pepper) dose-dependently inhibited oxidation of fatty acid, linoleic acid in presence of soybean lipoxygenase. Among the spices tested, cloves exhibited highest while onion showed least antioxidant activity. The relative antioxidant activities decreased in the order of cloves, cinnamon, pepper, ginger, garlic, mint and onion. Spice mix namely ginger, onion and garlic; onion and ginger; ginger and garlic showed cumulative inhibition of lipid peroxidation thus exhibiting their synergistic antioxidant activity. The antioxidant activity of spice extracts were retained even after boiling for 30 min at 100 degrees C, indicating that the spice constituents were resistant to thermal denaturation. The antioxidant activity of these dietary spices suggest that in addition to imparting flavor to the food, they possess potential health benefits by inhibiting the lipid peroxidation.     

Antioxidant activity of pine bark constituents

A modified in vitro lipid peroxidation inhibition assay was used to guide the fractionation and the isolation of antioxidative principles of Fnnish pine bark extract. This approach yielded 3,4-dihydroxybenzoic acid (protocatechuic acid) and taxifolin-3-O-beta-glucopyranoside as major antioxidative compounds from the plant material. The structural elucidation of these compounds was undertaken with the help of HPLC-DAD and HPLC-ESI-MS analyses. Their IC50 values, in comparison to trolox (6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid), were: trolox (1.78 +/- 0.56 microM) < protocatechuic acid (5.77 +/- 1.63 microM) < taxifolin-3-O-beta-glucopyranoside (16.30 +/- 1.98 microM). The method for the determination of antioxidant activity proved reproducible and quick for routine analyses with 96 well plates.     

Antioxidant and biological activity of melatonin

Neurohormone melatonin controls the circadian rhytmicity of some biological processes, unites the functions of nervous, endocrine and immune systems. Melatonin is a powerful bioantioxidant, capable to be dissolved in water and lipids, runs through membranes and barriers, accumulates in cell nuclei and protects DNA from oxidative stress. Melatonin displays immunomodulating, radioprotective and antitumor activities.     

Antioxidant activity of anti-inflammatory plant extracts

The antioxidant properties of twenty medical herbs used in the traditional Mediterranean and Chinese medicine were studied. Extracts from Forsythia suspensa, Helichrysum italicum, Scrophularia auriculata, Inula viscosa, Coptis chinensis, Poria cocos and Scutellaria baicalensis had previously shown anti-inflammatory activity in different experimental models. Using free radical-generating systems H. italicum. I. viscosa and F. suspensa protected against enzymatic and non-enzymatic lipid peroxidation in model membranes and also showed scavenging property on the superoxide radical. All extracts were assayed at a concentration of 100 microg/ml. Most of the extracts were weak scavengers of the hydroxyl radical and C. chinensis and P. cocos exhibited the highest scavenging activity. Although S. baicalensis inhibited the lipid peroxidation in rat liver microsomes and red blood cells, the extract showed inhibitory actions on aminopyrine N-demethylase and xanthine oxidase activities as well as an pro-oxidant effect observed in the Fe3+-EDTA-H2O2 system. The results of the present work suggest that the anti-inflammatory activities of the same extracts could be explained, at least in part, by their antioxidant properties.     

Antioxidant activity of oxygen-containing aromatic compounds

Inhibition efficiency (antioxidant activity) of 26 oxygen-containing aromatic compounds was studied in methemalbumin-H₂O₂-o-phenylenediamine (PDA) or tetramethylbenzidine (TMB) pseudoperoxidase system at 20°C in buffered physiological solution (pH 7.4) containing 6% DMF and 0.25% DMSO. The inhibitor’s efficiency was quantitatively characterized by the inhibition constants (K _i, μM) or the inhibition degree (%). K _i values varied in the range of 4 to 500 μM and were influenced by a substrate, the structure of an inhibitor, hydroxyl groups, electron-donating substituents in aromatic ring, and steric hindrances. The type of inhibition at cooxidation of eight pairs was noncompetitive, and that of five pairs was mixed and determined by the substrate nature and the inhibitor structure. Lignin phenolic compounds of guaiacyl and syringal series exhibited high antioxidant activity (K _i in the range of 10–300 μM), and their efficiency decreased in the following order: caffeic acid > synapaldehyde > syringic acid > coniferyl aldehyde > para-hydroxycoumaric acid.     

Antioxidant activity of N-carboxymethyl chitosan oligosaccharides

Three N-carboxymethyl chitosan oligosaccharides (N-CMCOSs) with different degrees of substitution (NA: 0.28, NB: 0.41, and NC: 0.54, respectively) were prepared by the control of the amount of glyoxylic acid in the etherification process of chitosan oligosaccharide (COS). Their antioxidant activities were evaluated by the scavenging of 1,1-diphenyl-2-picrylhrazyl radical (DPPH) radical, superoxide anion and determination of reducing power. With the increasing of substituting degree, the scavenging activity of N-CMCOSs against DPPH radical decreased and reducing power increased. As for superoxide anion scavenging, the order is NB>NC>NA. The difference may be related to the different radical scavenging mechanisms and donating effect of substituting carboxymethyl group.     

Antioxidant activity of novel chitin derivative

Novel water-soluble chitin derivative was prepared by chemical modification to evaluate antioxidant activities by free radical scavenging potential using electron spin resonance spin trapping technique. Aminoethyl-chitin (AEC) exhibited free radical scavenging activities against 1,1-diphenyl-2-picrylhydrazyl (DPPH), hydroxyl, superoxide, and peroxyl radicals. AEC quenched DPPH and peroxyl radical over 55% and 59% at 4mg/mL, and also suppressed superoixde radical over 58% at 2mg/mL. Especially, AEC was more active against hydroxyl radical, and scavenging ratio was 92.2% at 0.12mg/mL. These results suggested that free amino group in the -CH(2)CH(2)NH(2) plays an important role in the free radical scavenging activity. In addition, cytotoxic effect of AEC was assessed using human lung fibroblast (MRC-5) cell line, and AEC showed less toxic against MRC-5.