Characterization of the radical-scavenging reaction of 2-O-substituted ascorbic acid derivatives, AA-2G, AA-2P, and AA-2S: a kinetic and stoichiometric study

The aim of this study was to characterize the antioxidant activity of three ascorbic acid (AA) derivatives O-substituted at the C-2 position of AA: ascorbic acid 2-glucoside (AA-2G), ascorbic acid 2-phosphate (AA-2P), and ascorbic acid 2-sulfate (AA-2S). The radical-scavenging activities of these AA derivatives and some common low molecular-weight antioxidants such as uric acid or glutathione against 1,1-diphenyl-picrylhydrazyl (DPPH) radical, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS+), or galvinoxyl radical were kinetically and stoichiometrically evaluated under pH-controlled conditions. Those AA derivatives slowly and continuously reacted with DPPH radical and ABTS+, but not with galvinoxyl radical. They effectively reacted with DPPH radical under acidic conditions and with ABTS+ under neutral conditions. In contrast, AA immediately quenched all species of radicals tested at all pH values investigated. The reactivity of Trolox, a water-soluble vitamin E analogue, was comparable to that of AA in terms of kinetics and stoichiometrics. Uric acid and glutathione exhibited long-lasting radical-scavenging activity against these radicals under certain pH conditions. The radical-scavenging profiles of AA derivatives were closer to those of uric acid and glutathione rather than to that of AA. The number of radicals scavenged by one molecule of AA derivatives, uric acid, or glutathione was equal to or greater than that by AA or Trolox under the appropriate conditions. These data suggest the potential usage of AA derivatives as radical scavengers.     

Interactions of peroxynitrite with uric acid in the presence of ascorbate and thiols: implications for uncoupling endothelial nitric oxide synthase

It has been suggested that uric acid acts as a peroxynitrite scavenger although it may also stimulate lipid peroxidation. To gain insight into how uric acid may act as an antioxidant, we used electron spin resonance to study the reaction of uric acid and plasma antioxidants with ONOO-. Peroxynitrite reacted with typical plasma concentrations of urate 16-fold faster than with ascorbate and 3-fold faster than cysteine. Xanthine but not other purine-analogs also reacted with peroxynitrite. The reaction between ONOO- and urate produced a carbon-centered free radical, which was inhibited by either ascorbate or cysteine. Moreover, scavenging of ONOO- by urate was significantly increased in the presence of ascorbate and cysteine. An important effect of ONOO- is oxidation of tetrahydrobiopterin, leading to uncoupling of nitric oxide synthase. The protection of eNOS function by urate, ascorbate and thiols in ONOO(-)-treated bovine aortic endothelial cells (BAECs) was, therefore, investigated by measuring superoxide and NO using the spin probe 1-hydroxy-3-methoxycarbonyl-2,2,5,5-tetramethyl-pyrrolidine (CMH) and the NO-spin trap Fe[DETC]2. Peroxynitrite increased superoxide and decreased NO production by eNOS indicating eNOS uncoupling. Urate partially prevented this effect of ONOO- while treatment of BAECs with the combination of either urate with ascorbate or urate with cysteine completely prevented eNOS uncoupling caused by ONOO-. We conclude that the reducing and acidic properties of urate are important in effective scavenging of peroxynitrite and that cysteine and ascorbate markedly augment urate's antioxidant effect by reducing urate-derived radicals.     

DPPH and oxygen free radicals as pro-oxidant of biomolecules.

Numerous investigations exist about the alterations that oxygen free radicals can provoke on biomolecules; these modifications can be prevented and/or reversed by different antioxidants agents. On the other hand, 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), a stable nitrogen synthetic radical, is used to evaluate the antioxidant capacity of medicinal herbal products; however, the structural changes that this radical provoke on the herbal active principles are not clear yet. In this work, we compared the redox reactivity of oxygen free radicals and DPPH radical on phospholipids and protein thiol groups present in rat liver microsomes. Cu2+/ascorbate was used as generator system of oxygen free radical and as antioxidant, an extract of Buddleja globosa's leaves. Cu2+/ascorbate provoked microsomal lipid peroxidation, microsomal thiols oxidation and oxygen consumption; all of these phenomena were inhibited by B. globosa extract. On the other hand, DPPH was bleached in different extension by the herbal extract and phosphatidyl choline; beside, DPPH decreased microsomal thiols content, but this phenomenon were not prevented by the herbal extract. Furthermore, DPPH did not induce oxygen consumption and neither modified the oxygen consumption induced by Cu2+/ascorbate. Distinct redox mechanisms may explain the differences between the reactivity of DPPH and oxygen free radicals on biomolecules, which is discussed.     

茉莉花挥发油清除自由基活性的研究

目的：从清除1,1－二苯基－2－苦苯肼自由基（DPPH?）、羟自由基（? OH）、超氧阴离子自由基（O2?－）3个方面,研究茉莉花挥发油清除自由基活性。方法采用水蒸气蒸馏法提取茉莉花挥发油,从其清除DPPH?、? OH和O2?－能力3个方面进行考察,并以常用抗氧化剂L－抗坏血酸为对照作比较,通过计算半数抑制浓度（ IC50）评价茉莉花挥发油清除,在供试质量浓度范围内,呈一定量效关系,其 IC50分别为153．548μg?mL －1、56．481μg? mL －1和133．586μg? mL －1。结论茉莉花挥发油具有良好的清除自由基活性,是一种新型天然抗氧化物质来源。     

Determination of antioxidant activity of some drugs using high-pressure liquid chromatography

The antioxidant activities of different drugs like acetylsalicylic acid, nimesulide, dapsone, methlydopa, rifampicin and the well known antioxidants ascorbic acid and quercetin were assessed using the stable free radical alpha,alpha-diphenyl-beta-picrylhydrazyl (DPPH). DPPH is easily soluble at lower concentrations in methanol. It has a deep violet color. The changes in color are monitored calorimetrically. The measurements were made using HPLC at wavelengths 256 nm and 517 nm. The interactions between different drugs with DPPH were studied. All the compounds tested reduced DPPH. This method can be used to investigate oxygen free radical scavenging activity of drug candidates.     

Determination of DPPH free radical scavenging activity by reversed-phase HPLC: a sensitive screening method for polyherbal formulations

The colorimetric method of evaluation of antioxidant activity by scavenging 1,1-diphenyl-2-picrylhydrazyl (DPPH) free radical is with certain shortcomings like failure to indicate antioxidant activity of certain drugs and interference from color pigments of natural products. A specific HPLC method was developed for evaluating the DPPH free radical scavenging activity of commercial polyherbal formulations using a LiChrospher 100 RP-18e column (250 mm x 4 mm, 5 microM). The mobile phase was a mixture of methanol and water (80:20, v/v) pumped at a flow rate of 1 mL/min. The DPPH peaks were monitored at 517 nm. The method was standardized using known antioxidants such as ascorbic acid, 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (trolox), probucol and alpha-tocopherol. The 50% radical scavenging activity (IC50) determined by the HPLC method correlated well with that of colorimetry. This HPLC method was applied for the estimation of free radical scavenging activity of Silymarin and a few commercial hepatoprotective polyherbal formulations. While the colorimetric method failed to estimate the free radical scavenging activity of polyherbal formulations, HPLC method was free from interferences and was specific. The HPLC method is sensitive and can be used as a quality control tool for the rapid determination of free radical scavenging activity of variety of products including plant extracts, foods, drugs and polyherbal formulations.     

Antioxidative activities and the total phenolic contents of tonic Chinese Medicinal Herbs

Chinese medicated diet is an everyday practice in China. In this study, 16 commonly used soup making tonic Chinese medicinal herbs were selected for antioxidative capacities by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and ferric reducing antioxidant power (FRAP), and the total phenolic contents of these herbal extracts were measured by the Folin-Ciocalteu method. It confirmed that drinking tonic soups could supplement total antioxidants intake. Amongst the tested herbal extracts, extracts of Canarium album Raeusch., Flos caryophylli and Fructus amomi were found to have the highest antioxidative activities in both DPPH and FRAP assays. Their antioxidative activities were comparable to ascorbic acid and butylated hydroxytoluene. Thus, these herbs are safe and inexpensive sources of natural antioxidants. A significant relationship between the antioxidative effects and total phenolic contents were found, indicating phenolic compounds are the major contributor of antioxidative capacities of these herbs. In addition, a strong correlation between DPPH assay and FRAP assay implied that antioxidants in these herbs were capable of scavenging free radicals and reducing oxidants.     

Antioxidant properties of β-seleno amines against lipid peroxidation in rat brain and liver

β-Seleno amines were screened for in vitro antioxidant activity. The compounds (C1-C4) were tested against lipid peroxidation induced by iron and sodium nitroprusside in rat brain and liver homogenates. The compounds showed inhibition against thiobarbituric acid reactive species (TBARS) induced by different pro-oxidants (10μM FeSO(4) and 5μM sodium nitroprusside (SNP) in rat brain and liver homogenates. The compounds exhibited strong antioxidant activity in 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical and phosphomolybdenum assays. The IC(50) values revealed that the β-seleno amines in which the amino group was protected with protecting groups tert-butyloxycarbonyl (Boc) and Tosyl (Ts) groups showed better antioxidant profiles compared to the free monoselenides. The total antioxidant activity of C1, C2, C3 and C4 were found to be 85.2±11.5, 114±7.9, 138±8.5, 125.81±5.2μM/ml of ascorbic acid respectively. Therefore, these compounds may be used as synthetic antioxidants.     

化合物3,4,5-三羟基-N-[2-(4-羟基苯基)乙基]苯甲酰胺的抗氧化活性

目的对化合物3,4,5-三羟基-N-[2-(4-羟基苯基)乙基]苯甲酰胺(3,4,5-trihydroxy-N-[2-(4-hydroxyphenyl)ethyl]-benzamide,THHEB)的抗氧化活性进行研究。方法通过测定对有机自由基1,1-二苯基苦基苯肼(1,1-diphenyl-2-picrylhydrazyl,DPPH)的清除能力、6-羟基-2,5,7,8-四甲基苯并二氢吡喃-2-羧酸(6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid,Trolox)当量抗氧化能力(trolox-equivalent antioxidant capacity assay,TEAC),测定超氧自由基的清除活性实验、脂质过氧化法以及羟基自由基诱导DNA损伤的方法评价THHEB的抗氧化活性。结果5种方法检测结果均显示,THHEB具有很强的清除自由基的活性。其中,THHEB对稳定自由基DPPH和超氧自由基的清除能力超过抗坏血酸的相应活性,其IC50值分别为22.8、2.5μmol.L-1。用TEAC方法测定THHEB总的抗氧化能力大约为0.6,也比L-抗坏血酸相应值高。脂质过氧化法测定的THHEB活性要弱于著名的抗氧化化合物2,6-二叔基对甲苯酚(butylated hydroxytoluene,BHT)。此外,非常小浓度比如4μmo.lL-1的THHEB对羟基自由基导致的pBR322 DNA链断裂具有显著的保护作用。结论THHEB具有很强的清除自由基的活性。     

Synthesis and free radical scavenging activity of coumarin derivatives containing a 2-methylbenzothiazoline motif

Coumarin and benzothiazole scaffolds can be found in a number of natural or synthetic antioxidants. In an effort to develop a novel radical scavenger and potential antioxidant, a series of coumarin derivatives containing 2‐methylbenzothiazoline motif and related compounds was synthesized and evaluated for their DPPH (1,1‐diphenyl‐2‐picrylhydrazyl) and ABTS^?+ (2,2′‐azinobis(3‐ethylbenzothiazoline‐6‐sulfonic acid) radicals scavenging activities. Among them, 7‐hydroxy‐3‐(2‐methyl‐2,3‐dihydrobenzo[d]thiazol‐2‐yl)‐2H‐chromen‐2‐one ( 3e ) has shown a significant free radical scavenging activity. From the structure–activity point of view, it was found that phenolic coumarin ring and benzothiazoline moiety in target compounds may contribute to the scavenging activity against free radicals.     

Estimate of antioxidant capacity and lipid peroxidation in plasma of healthy subjects

Serum contains various antioxidant molecules that may provide important protection against free radical attack. The aim of this work was to assess the total antioxidant capacity of plasma and a marker of lipid per oxidation [(thiobarbituric acid-reactive substances (TBARS)] in plasma of healthy smoking and non-smoking young and elderly subjects. In addition, we investigated plasma concentrations of α-tocopherol, β-carotene, and ascorbic acid. In in vitro experiments, the effects of exogenous compounds (ascorbic acid, uric acid, Trolox) on total ferric-reducing activity of plasma (FRAP) were also tested. We demonstrated that total antioxidant capacity of plasma obtained from healthy non-smoking young subjects was significantly higher than plasma antioxidant capacity of smoking elderly subjects. The concentration of TBARS in young non-smoking volunteers was lower than that in young smokers. The concentration of TBARS in elderly non-smoking volunteers was lower than in elderly smokers. Plasma concentrations of alpha-tocopherol, beta-carotene and ascorbic acid were significantly lower in elderly smoker than in elderly non-smokers of the same age. No difference in the plasma levels of alpha-tocopherol, beta-carotene and ascorbic acid were found in 22-year-old smoking and non-smoking subjects. In vitro addition of ascorbic acid, uric acid, or Trolox to plasma samples significantly increased their total antioxidant capacity. Decrease of FRAP values and increase of TBARS concentrations is a significant physiologic condition of the aging process. Supplementation of antioxidants could be useful for the enhancement of antioxidant screen in plasma.     

Hydrogen peroxide scavenging, antioxidant and anti-radical activity of some phenolic acids.

Some water-soluble phenolic acids were investigated as antioxidants, scavengers of hydrogen peroxide (H(2)O(2)) and scavengers of 1,1-diphenyl-2-picrylhydrazyl radical (DPPH(*)). The strongest antioxidant, scavenging of H(2)O(2) and DPPH(*) radical activity was exhibited by 3,4,5-trihydroxybenzoic (gallic) acid and 1,2,3-trihydroxybenzene (pyrogallol) with three hydroxyl groups bonded to the aromatic ring in an ortho position in relation to each other. Phenolic acids with two hydroxyl groups bonded to aromatic ring in the ortho position, such as 3,4-dihydroxycinnamic (caffeic), 3,4-dihydroxybenzoic (protocatechuic) and 2,3-dihydroxybenzoic (o-pyrocatechuic) acids, showed strong antioxidant and anti-radical activity; however, it was lower than that of 3,4,5-trihydroxybenzoic acid or 1,2,3-trihydroxybenzene. 3,5-Dihydroxybenzoic (alpha-resorcylic) and 2,4-dihydroxybenzoic (beta-resorcylic) acids with two hydroxyls bonded in the meta position in relation to each other showed moderate antioxidant and low DPPH(*) and hydrogen peroxide scavenging activity. Compounds with one hydroxyl group such as 3-hydroxybenzoic, 4-hydroxyphenylacetic and 2-hydroxybenzoic (salicylic) acids, exhibited the lowest anti-radical and antioxidant activity. The results obtained show that the antioxidant and anti-radical activity of phenolic acids correlated positively with the number of hydroxyl groups bonded to the aromatic ring. The model of an ortho substitution of hydroxyl groups to the aromatic ring seems to be adequate for antioxidant and H(2)O(2) or DPPH(*) scavenging activity of phenolic acids.     

Antioxidant activity of saponins isolated from ivy: alpha-hederin, hederasaponin-C, hederacolchiside-E and hederacolchiside-F

The antioxidant activities of alpha-hederin and hederasaponin-C from Hedera helix, and hederacolchisides-E and -F from Hedera colchica were investigated, in this study. The antioxidant properties of the saponins were evaluated using different antioxidant tests: 1,1-di-phenyl-2-picryl-hydrazyl (DPPH.) free radical scavenging, total antioxidant activity, reducing power, superoxide anion radical scavenging, hydrogen peroxide scavenging, and metal chelating activities. Alpha-hederin, hederasaponin-C, as well as hederacolchisides-E and -F exhibited a strong total antioxidant activity. At the concentration of 75 pg/mL, these saponins showed 94, 86, 88 and 75% inhibition on lipid peroxidation of linoleic acid emulsion,respectively. These various antioxidant activities were compared with model antioxidants such as a-tocopherol, butylated hydroxyanisole (BHA) and butylated hydroxytoluene (BHT).     

Flavonoids are scavengers of superoxide anions

Seven flavonoids and three non-flavonoid antioxidants, i.e. butylated hydroxyanisole, chlorpromazine and BW 755 C, were studied as potential scavengers of oxygen free radicals. Superoxide anions were generated enzymatically in a xanthine-xanthine oxidase system and non-enzymatically in a phenazine methosulphate-NADH system, and assayed by reduction of nitro blue tetrazolium. The generation of malonaldehyde (MDA) by the ascorbate-stimulated air-oxidised boiled rat liver microsomes was considered as an index of the non-enzymatic formation of hydroxyl radicals. Flavonoids but not non-flavonoid antioxidants lowered the concentration of detectable superoxide anions in both enzymic and non-enzymic systems which generated these SOD-sensitive radicals. The most effective inhibitors of superoxide anions were quercetin, myricetin and rutin. Four out of seven investigated flavonoids seemed also to suppress the activity of xanthine oxidase as measured by a decrease in uric acid biosynthesis. All ten investigated compounds inhibited the MDA formation by rat liver microsomes. Non-flavonoid antioxidants were more potent MDA inhibitors than flavonoids. It is concluded that antioxidant properties of flavonoids are effected mainly via scavenging of superoxide anions whereas non-flavonoid antioxidants act on further links of free radical chain reactions, most likely by scavenging of hydroxyl radicals.     

Dihydrolipoic acid--a universal antioxidant both in the membrane and in the aqueous phase. Reduction of peroxyl, ascorbyl and chromanoxyl radicals.

Thioctic (lipoic) acid is used as a therapeutic agent in a variety of diseases in which enhanced free radical peroxidation of membrane phospholipids has been shown to be a characteristic feature. It was suggested that the antioxidant properties of thioctic acid and its reduced form, dihydrolipoic acid, are at least in part responsible for the therapeutic potential. The reported results on the antioxidant efficiency of thioctic and dihydrolipoic acids obtained in oxidation models with complex multicomponent initiation systems are controversial. In the present work we used relatively simple oxidation systems to study the antioxidant effects of dihydrolipoic and thioctic acids based on their interactions with: (1) peroxyl radicals which are essential for the initiation of lipid peroxidation, (2) chromanoxyl radicals of vitamin E, and (3) ascorbyl radicals of vitamin C, the two major lipid- and water-soluble antioxidants, respectively. We demonstrated that: (1) dihydrolipoic acid (but not thioctic acid) was an efficient direct scavenger of peroxyl radicals generated in the aqueous phase by the water-soluble azoinitiator 2,2'-azobis(2-amidinopropane)-dihydrochloride, and in liposomes or in microsomal membranes by the lipid-soluble azoinitiator 2,2'-azobis(2,4-dimethylvaleronitrile); (2) both dihydrolipoic acid and thioctic acid did not interact directly with chromanoxyl radicals of vitamin E (or its synthetic homologues) generated in liposomes or in the membranes by three different ways: UV-irradiation, peroxyl radicals of 2,2'-azobis(2,4-dimethylvaleronitrile), or peroxyl radicals of linolenic acid formed by the lipoxygenase-catalyzed oxidation; and (3) dihydrolipoic acid (but not thioctic acid) reduced ascorbyl radicals (and dehydroascorbate) generated in the course of ascorbate oxidation by chromanoxyl radicals. This interaction resulted in ascorbate-mediated dihydrolipoic acid-dependent reduction of the vitamin E chromanoxyl radicals, i.e. vitamin E recycling. We conclude that dihydrolipoic acid may act as a strong direct chain-breaking antioxidant and may enhance the antioxidant potency of other antioxidants (ascorbate and vitamin E) in both the aqueous and the hydrophobic membraneous phases.     

Effect of nilvadipine in weak acidic medium by 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay

A new medium (pH 5.6 reached by addition of 0.1 mol/l acetate buffer, 37 degrees C, 60 min) was established for detecting anti-free radical compounds in the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay. DPPH bleaching activities of typical antioxidants appeared generally weaker at pH 8.0 (the measured ethanol solution pH by the classical DPPH assay method) than at pH 5.6. Nilvadipine (CAS 75530-68-6), a lipophilic calcium antagonist, enhanced the bleaching much more at pH 5.6 than at pH 8.0. Nifedipine (CAS 21829-25-4) and amiodipine (amiodipine besilate, CAS 88150-42-9) showed some effect, but the other five calcium antagonists failed to bleach DPPH at any pH tested (pH 4.4-8.0). Probucol and beta-carotene (standard antioxidant) showed nearly the same bleaching activity as nilvadipine. Captopril, glutathione and bilirubin were weaker anti-free radical compounds at pH 5.6. No intermediating participation of superoxide radicals and hydroxyl radicals were observed in the DPPH assay, both at pH 8.0 and 5.6. Thus, nilvadipine was shown to be an efficient free-radical scavenger only at around pH 5.6, a weak acidic condition which may occur as a result of inflammation and/or ischemia-reperfusion.     

Antioxidant and DNA damage protection potentials of selected phenolic acids

In this study, ten different phenolic acids (caffeic, chlorogenic, cinnamic, ferulic, gallic, p-hydroxybenzoic, protocatechuic, rosmarinic, syringic, and vanillic acids) were evaluated for their antioxidant and DNA damage protection potentials. Antioxidant activity was evaluated by using four different test systems named as β-carotene bleaching, DPPH free radical scavenging, reducing power and chelating effect. In all test systems, rosmarinic acid showed the maximum activity potential, while protocatechuic acid was determined as the weakest antioxidant in β-carotene bleaching, DPPH free radical scavenging, and chelating effect assays. Phenolic acids were also screened for their protective effects on pBR322 plasmid DNA against the mutagenic and toxic effects of UV and H₂O₂. Ferulic acid was found as the most active phytochemical among the others. Even at the lowest concentration value (0.002 mg/ml), ferulic acid protected all of the bands in the presence of H₂O₂ and UV. It is followed by caffeic, rosmarinic, and vanillic acids. On the other hand, cinnamic acid (at 0.002 mg/ml), gallic acid (at 0.002 mg/ml), p-hydroxybenzoic acid (at 0.002 and 0.004 mg/ml), and protocatechuic acid (at 0.002 and 0.004 mg/ml) could not protect plasmid DNA.     

Mangifera indica L. extract (Vimang) inhibits Fe2+-citrate-induced lipoperoxidation in isolated rat liver mitochondria.

The extract of Mangifera indica L. (Vimang) is able to prevent iron mediated mitochondrial damage by means of oxidation of reduced transition metals required for the production of superoxide and hydroxyl radicals and direct free radical scavenging activity. In this study we report for the first time the iron-complexing ability of Vimang as a primary mechanism for protection of rat liver mitochondria against Fe2+ -citrate-induced lipoperoxidation. Thiobarbituric acid reactive substances (TBARS) and antimycin A-insensitive oxygen consumption were used as quantitative measures of lipoperoxidation. Vimang at 10 microM mangiferin concentration equivalent induced near-full protection against 50 microM Fe2+ -citrate-induced mitochondrial swelling and loss of mitochondrial transmembrane potential (DeltaPsi). The IC50 value for Vimang protection against Fe2+ -citrate-induced mitochondrial TBARS formation (7.89+/-1.19 microM) was around 10 times lower than that for tert-butylhydroperoxide mitochondrial induction of TBARS formation. The extract also inhibited the iron citrate induction of mitochondrial antimycin A-insensitive oxygen consumption, stimulated oxygen consumption due to Fe2+ autoxidation and prevented Fe3+ ascorbate reduction. The extracted polyphenolic compound, mainly mangiferin, could form a complex with Fe2+, accelerating Fe2+ oxidation and the formation of more stable Fe3+ -polyphenol complexes, unable to participate in Fenton-type reactions and lipoperoxidation propagation phase. The strong DPPH radical scavenging activity with an apparent IC50 of 2.45+/-0.08 microM suggests that besides its iron-complexing capacity, Vimang could also protect mitochondria from Fe2+ -citrate lipoperoxidation through direct free radical scavenging ability, mainly lipoperoxyl and alcoxyl radicals, acting as both a chain-breaking and iron-complexing antioxidant. These results are of pharmacological relevance since Vimang could be a potential candidate for antioxidant therapy in diseases related to abnormal intracellular iron distribution or iron overload.     

Characterization of the radical scavenging and antioxidant activities of danshensu and salvianolic acid B.

Danshensu (3-(3,4-dihydroxyphenyl) lactic acid) and salvianolic acid B, two natural phenolic acids of caffeic acid derivatives isolated from Salvia miltiorrhiza root of the most widely used traditional Chinese medicine for the treatment of various cardiovascular diseases, have been reported to have potential protective effects from oxidative injury. To better understand their biological functions, the in vitro radical scavenging and antioxidant activities of danshensu and salvianolic acid B were evaluated along with vitamin C. Both danshensu and salvianolic acid B exhibited higher scavenging activities against free hydroxyl radicals (HO()), superoxide anion radicals (O(2)(-)), 1,1-diphenyl-2-picryl-hydrazyl (DPPH) radicals and 2-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid) (ABTS) radicals than vitamin C. In contrary, danshensu and salvianolic acid B showed weaker iron chelating and hydrogen peroxide (H(2)O(2)) scavenging activities than vitamin C. As expressed as vitamin C equivalent capacity (VCEAC), the relative VCEAC values (mg/100ml) were in the order of salvianolic acid B (18.59) > danshensu (12.89) > vitamin C (10.00) by ABTS radical assay. The protective efficiencies against hydrogen peroxide induced human vein vascular endothelial cell damage were correlated with their antioxidant activities. Analysis of structure-activity relationship of these two compounds showed that the condensation and conjugation of danshensu and caffeic acid appears important for antioxidant activity. These results indicated that danshensu and salvianolic acid B are efficient radical scavengers and antioxidants, and salvianolic acid B is superior to danshensu. Their radical scavenging and antioxidant properties might have potential applications in food and healthcare industry.     

Action of the novel antioxidants 4GBE43 and 2BBE43 against lipid peroxidation.

The action and the effect of the newly synthesized compounds 4GBE43 [N-(1,2-diethyltetrahydro-1H-pyrazol-4-yl)-4-[(2E)-3,7-diethyl-2,6-octadienyl] oxybenzamide] and 2BBE43 [2-(benzyloxy)-N-(1,2-diethyltetrahydro-1H-pyrazol-4-yl)benzamide] against lipid peroxidation were studied. 4GBE43 and 2BBE43 quenched the ESR signal of diphenylpicrylhydrazyl (DPPH), suggesting that 4GBE43 and 2BBE43 act as scavengers of free radicals and that each compound quenched 6 free radical molecules. These compounds suppressed the oxidation of methyl linoleate emulsions and soybean phosphatidylcholine liposomes by a free radical initiator, suggesting that these compounds quench the lipid peroxyl radical. 4GBE43 and 2BBE43 also suppressed the spontaneous oxidation of rat brain homogenates. The inhibitory effect of 2BBE43 was of the same order of magnitude (IC50) as that of probucol. The IC50 of 4GBE43 was on the same order of magnitude as that of alpha-tocopherol. However, 4GBE43 at 10(-4)-10(-5) M completely inhibited peroxidation, showing it to be more effective than alpha-tocopherol. These results suggest that 4GBE43 and 2BBE43 act as antioxidants by quenching the lipid peroxyl radical.