Effects of Mangifera indica L. aqueous extract (Vimang) on primary culture of rat hepatocytes

Vimang is an aqueous extract from stem bark of Mangifera indica L. (Mango) with pharmacological properties. It is a mixture of polyphenols (as main components), terpenoids, steroids, fatty acids and microelements. In the present work we studied the cytotoxic effects of Vimang on rat hepatocytes, possible interactions of the extract with drug-metabolizing enzymes and its effects on GSH levels and lipid peroxidation. No cytotoxic effects were observed after 24 h exposure to Vimang of up to 1000 μg/mL, while a moderate cytotoxicity was observed after 48 and 72 h of exposure at higher concentrations (500 and 1000 μg/mL). The effect of the extract (50–400 μg/mL) on several P450 isozymes was evaluated. Exposure of hepatocytes to Vimang at concentrations of up to 100 μg/mL produced a significant reduction (60%) in 7-methoxyresorufin-O-demethylase (MROD; CYP1A2) activity, an increase (50%) in 7-penthoxyresorufin-O-depentylase (PROD; CYP2B1) activity, while no significant effect was observed with other isozymes. To our knowledge, this is the first report regarding the modulation of the activity of the P450 system by an extract of Mangifera indica L. The antioxidant properties of Vimang were also evaluated in t-butyl-hydroperoxide-treated hepatocytes. A 36-h pre-treatment of cells with Vimang (25–200 μg/mL) strongly inhibited the decrease of GSH levels and lipid peroxidation induced by t-butyl-hydroperoxide dose- and time-dependently.     

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.     

Protective effect of puerariae radix on oxidative stress induced by hydrogen peroxide and streptozotocin

This study evaluated the protective effect of Puerariae radix against the oxidative stress induced by hydrogen peroxide (H2O2) and streptozotocin in vitro and in vivo, respectively. The ethanol extract scavenged intracellular reactive oxygen species (ROS), and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and prevented lipid peroxidation. This radical scavenging activity of the ethanol extract protected the cell viability of Chinese hamster lung fibroblast (V79-4) cells exposed to H2O2. Furthermore, this extract reduced the formation of apoptotic cells induced by H2O2, which was demonstrated by the decreased number of sub G(1) hypo-diploid cells and apoptotic cell body formation. The extract increased the activities of the cellular antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT). Administration of the extract to the streptozotocin induced diabetic rats decreased the blood glucose levels. The diabetic rats showed low activities of superoxide dismutase and catalase in the liver, and the ethanol extract increased the CAT activity. The increased level of lipid peroxidation in the diabetic rats reverted to near normal levels after being treated with the extract. This study showed that Puerariae radix was effective in the amelioration of diabetes, which may be a consequence of its antioxidant potential.     

丹酚酸A对氧自由基引起的大鼠心脏和肝脏线粒体损伤的保护作用(英文)

已往的研究表明丹酚酸A有很强的抗氧化活性。本文研究了丹酚酸A对氧自由基引起的大鼠心脏和肝脏线粒体损伤的保护作用。结果表明,丹酚酸A可抑制铁一半胱氨酸引起的线粒体脂质过氧化和ATP酶活性的丧失。脂质过氧化引起的心脏和肝脏线粒体肿胀以及肝脏线粒体膜流动性下降均可被丹酚酸A抑制。同时丹酚酸A对超氧阴离子和羟自由基具有清除作用。进一步证明丹酚酸A具有抗氧化活性。     

d-儿茶素-3-O-β-D-葡萄糖苷的抗氧化作用(英文)

目的　研究粘萎陵菜含有的一种化合物 ,d 儿茶素 3 O β D 葡萄糖苷 (CGS)的保肝作用机制。方法　测定CGS在体外对NADPH 维生素C和Fe2 + 半胱氨酸系统诱发的微粒体脂质过氧化反应(丙二醛形成 )的影响 ,对黄嘌呤 黄嘌呤氧化酶系统超氧阴离子自由基产生 (还原型细胞色素C形成 )的影响 ;在体内对CCl4和乙醇诱发的小鼠肝丙二醛形成的影响。结果　体外CGS 1 0 0 μmol·L-1 能明显抑制NADPH 维生素C和Fe2 + 半胱氨酸系统诱发的大鼠脑、肝、肾微粒体丙二醛形成及黄嘌呤 黄嘌呤氧化酶系统超氧阴离子自由基的产生。在体内能抑制CCl4和乙醇诱发的小鼠肝脂质丙二醛形成。结论　CGS具有抗氧化作用     

Interaction of Vimang (Mangifera indica L. extract) with Fe(III) improves its antioxidant and cytoprotecting activity.

A standard aqueous stem bark extract from selected species of Mangifera indica L. (Anacardiaceae)--Vimang, whose major polyphenolic component is mangiferin, displays potent in vitro and in vivo antioxidant activity. The present study provides evidence that the Vimang-Fe(III) mixture is more effective at scavenging 2,2-diphenyl-1-picrylhydrazyl (DPPH) and superoxide radicals, as well as in protecting against t-butyl hydroperoxide-induced mitochondrial lipid peroxidation and hypoxia/reoxygenation-induced hepatocytes injury, compared to Vimang alone. Voltammetric assays demonstrated that Vimang, in line with the high mangiferin content of the extract, behaves electrochemically like mangiferin, as well as interacts with Fe(III) in close similarity with mangiferin's interaction with the cation. These results justify the high efficiency of Vimang as an agent protecting from iron-induced oxidative damage. We propose Vimang as a potential therapy against the deleterious action of reactive oxygen species generated during iron-overload, such as that occurring in diseases like beta-thalassemia, Friedreich's ataxia and haemochromatosis.     

“新冠三方”的体外抗氧化作用比较

目的 平行比较“新冠三方”(清肺排毒汤、化湿败毒方和宣肺败毒方,以下简称“三方”)的体外抗氧化作用。方法在非细胞体系中,采用FRAP法考察三方的总抗氧化能力;通过DPPH法考察三方对DPPH自由基的清除作用;采用NBT还原法考察三方对超氧阴离子的清除作用;通过基于终产物丙二醛的荧光测定法考察三方对羟自由基的清除作用;用FeSO4体外诱导大鼠肝匀浆MDA法考察三方对抗脂质过氧化的作用。依据以上5个抗氧化指标,平行比较三方提取物在非细胞体系的抗氧化能力。进一步地,在脂多糖活化的RAW264.7细胞模型上,分别使用L-012探针和MitoSOX线粒体超氧化物红色荧光探针检测胞质与线粒体活性氧(reactive oxygen species,ROS)的生成情况;通过光泽精探针检测胞质NADPH氧化酶活性,以平行比较三方提取物在细胞体系的抗氧化能力。结果 在非细胞体系中,三方均能剂量依赖地清除DPPH自由基、超氧阴离子和羟自由基,并且能有效对抗脂质过氧化的发生。在等提取物浓度下,三方对DPPH自由基与超氧阴离子的清除作用相当,总抗氧化能力相当,而化湿败毒方在清除羟自由基和对抗脂质过氧化方面表现更...     

The prophylactic protective effect of sesamol against ferric–nitrilotriacetate-induced acute renal injury in mice

The aim of this study was to examine the prophylactic protective effects of 3,4-methylenedioxyphenol (sesamol) on ferric-nitrilotriacetate (Fe-NTA)-induced acute renal damage in mice. We induced acute renal injury in mice by treating them with 4 mg/kg of Fe-NTA for 3h. We used blood biochemistry, creatinine clearance, and histological examinations to assess renal function. With a high-performance chemiluminescence analyzer, we also determined the hydroxyl radical and superoxide anion levels (free radicals) generated. Renal xanthine oxidase activities were also assessed. Sesamol inhibited Fe-NTA-induced acute renal injury, renal lipid peroxidation, the levels of renal hydroxyl radical and superoxide anion generated, and the activity of xanthine oxidase in mice. Therefore, we concluded that sesamol protected mice against Fe-NTA-induced oxidative-stress-associated acute renal injury by at least partially inhibiting the production of reactive oxygen species.     

Hydroxyl radical scavenging action of tinoridine

Radical scavenging action of tinoridine, a non-steroidal anti-inflammatory drug with a potent anti-peroxidative activity, was investigated. Tinoridine reduced a stable free radical, diphenyl-p-picryl-hydrazyl, in the molar ratio of about 1:2, indicating its free radical scavenging ability. Tinoridine inhibited the lipid peroxidation in rat liver microsomes induced by xanthine-xanthine oxidase system in the presence of ADP and Fe2+, in which hydroxyl radical (. OH) is formed. Tinoridine was demonstrated to be oxidized in the course of the lipid peroxidation by following the fluorescence derived from the oxidation product of tinoridine. It was also oxidized by the xanthine-xanthine oxidase system in the presence of Fe2+, but its oxidation was slow in the absence of Fe2+ and almost completely inhibited by catalase. Tinoridine was also oxidized by H2O2-Fe2+ system producing . OH (Fenton reaction), but it did not affect the reduction of cytochrome c caused by superoxide radical. These results indicate that tinoridine is able to scavenge . OH and the main active oxygen species responsible for the lipid peroxidation is . OH. The anti-peroxidative and . OH scavenging ability of tinoridine should contribute to its anti-inflammatory action.     

丹酚酸B镁盐对自由基的清除作用和对脂质过氧化的抑制作用(英文)

AIM: To study the effect of magnesium lithospermate B (MLB) on the lipid peroxidation and on its free radical scavenging activity. METHODS: MLB was incubated in rat tissue homogenate or in a free radical generating system. MLB induced inhibition of lipid peroxidation and its scavenging activity on superoxide anions and hydroxyl radicals was studied using colorimetric estimation. RESULTS: MLB inhibited the lipid peroxidation induced by either an auto-oxidant or Fe2+/VitC in vitro, in the liver homogenate, the inhibitory rate of MLB (10 mg/L) being 69.2% and 57.7%, respectively. MLB (25 and 50 mg/kg) decreased the amount of thiobarbituric acid reactive substances (TBARS) in rat serum, liver, kidney, and heart. However, it did not inhibit the lipid peroxidation of brain homogenate ex vivo. MLB scavenged superoxide anions generated from xanthine/xanthine oxidase system and iron-dependent hydroxyl radicals. CONCLUSION: MLB is an inhibitor of lipid peroxidation and scavenge superoxide anions and hydroxyl radicals both in vitro and ex vivo.     

Free radical scavenging and inhibition of lipid peroxidation by beta-blockers and by agents that interfere with calcium metabolism. A physiologically-significant process?

It has been proposed that beta-blockers and agents affecting Ca2+ metabolism might exert cardioprotective actions because of their ability to act as antioxidants in vivo. The feasibility of this proposal was tested by examining the reaction of a series of such compounds with various oxygen-derived species. None of the compounds tested was sufficiently reactive with superoxide radical, hydrogen peroxide or hypochlorous acid for scavenging of these species to be feasible in vivo at the drug concentrations present in patients given the usual therapeutic doses. All the drugs tested were powerful scavengers of hydroxyl radical except for flunarizine, which stimulated iron ion-dependent hydroxyl radical generation from hydrogen peroxide. However, none of the drugs significantly inhibited production of hydroxyl radicals in this system. Propranolol, verapamil and flunarizine had significant inhibitory effects on the peroxidation of rat liver microsomes in the presence of iron ions and ascorbic acid. All three compounds exerted weaker inhibitory effects on peroxidation of arachidonic acid caused by a mixture of myoglobin and H2O2: pindolol stimulated peroxidation in this system. It is concluded that the ability of beta-blockers and "Ca(2+)-blockers" to inhibit lipid peroxidation varies with the lipid substrate used and the mechanism by which peroxidation is induced. We conclude that suggestions that beta-blockers and "Ca(2+)-blockers" exert antioxidant effects in vivo are not well founded, although there is a possibility that verapamil and propranolol might have some inhibitory effects against peroxidation if they accumulate in membranes to a sufficiently-high concentration in vivo. We could not confirm the reported ability of propranolol to inhibit the enzyme xanthine oxidase.     

Protective effects of Mangifera indica L extract (Vimang), and its major component mangiferin, on iron-induced oxidative damage to rat serum and liver.

In vivo preventive effects of a Mangifera indica L extract (Vimang) or its major component mangiferin on iron overload injury have been studied in rats given respectively, 50, 100, 250 mg kg(-1) body weight of Vimang, or 40 mg kg(-1) body weight of mangiferin, for 7 days prior to, and for 7 days following the administration of toxic amounts of iron-dextran. Both Vimang or mangiferin treatment prevented iron overload in serum as well as liver oxidative stress, decreased serum and liver lipid peroxidation, serum GPx activity, and increased serum and liver GSH, serum SOD and the animals overall antioxidant condition. Serum iron concentration was decreased although at higher doses, Vimang tended to increase it; percent tranferrin saturation, liver weight/body mass ratios, liver iron content was decreased. Treatment increased serum iron-binding capacity and decreased serum levels of aspartate-amine transferase (ASAT) and alanine-amine transferase (ALAT), as well as the number of abnormal Kupffer cells in iron-loaded livers. It is suggested that besides acting as antioxidants, Vimang extract or its mangiferin component decrease liver iron by increasing its excretion. Complementing earlier in vitro results from our group, it appears possible to support the hypothesis that Vimang and mangiferin present therapeutically useful effects in iron overload related diseases.     

In vitro Antioxidant Studies of Fruits of Artemisia nilagirica (Clarke) Pamp

Antioxidant potential of fruits of Artemisia nilagirica was studied using different in vitro models like 1,1-diphenyl-2-picryl hydrazyl, 2,2-azinobis-(3-ethylbenzothizoline-6-sulphonate), nitric oxide, superoxide, hydroxyl radical and lipid peroxidation. Both the ethanol and aqueous extracts of A. nilagirica fruits at 500 μg/ml showed maximum scavenging activity (89.33% and 89.14%) in quenching 1,1-diphenyl-2-picryl hydrazyl radical. The ethanol extract showed better scavenging activity (69.78%) of 1,1-diphenyl-2-picryl hydrazyl radical followed by the scavenging of nitric oxide radical (73.25%) compared to aqueous extract. In contrast, hydroxyl and superoxide radicals were effectively scavenged by aqueous extract. Total antioxidant capacity of ethanol and aqueous extracts at 500 μg/ml concentration was found to be 56.21 and 62.78 mg ascorbic acid equivalents, respectively. However, both the extracts showed only moderate lipid peroxidation inhibition activity. They were also found to contain considerable total phenols and flavonoids suggesting their role as an effective free radical scavenger. These findings suggest that phenolics and flavonoids in the fruits provide substantial antioxidant activity.     

Antioxidative constituents fromPaeonia lactiflora

The ethanol extract of the peony root (Paeonia Lactiflora Pall, Paeoniaceae) as well as its major active components including gallic acid and methyl gallate were evaluated for their protective effects against free radical generation and lipid peroxidation. In addition, the protective effects against hydrogen peroxide-induced oxidative DNA damage in a mammalian cell line were examined. The ethanol extracts of the peony root (PREs) and its active constituents, gallic acid and methyl gallate, exhibited a significant free radical scavenging effect against 1,1-diphenyl-2-picryl hydrazine (DPPH) radical generation and had an inhibitory effect on lipid peroxidation, as measured by the level of malondialdehyde (MDA) formation. The PREs did not have any pro-oxidant effect. They strongly inhibited the hydrogen peroxide-induced DNA damage from NIH/3T3 fibroblasts, as assessed by single cell gel electrophoresis. Furthermore, the oral administration of 50% PRE (50% ethanol extract of peony root), gallic acid and methyl gallate potently inhibited the formation of micronucleated reticulocytes (MNRET) in the mouse peripheral blood induced by a KBrO3 treatment in vivo. Therefore, PREs containing gallic acid and methyl gallate may be a useful antigenotoxic antioxidant by scavenging free radicals, inhibiting lipid peroxidation and protecting against oxidative DNA damage without exhibiting any pro-oxidant effect.     

Inhibition of lipid peroxidation by pindolol

Among beta-blockers, including atenolol, metaproterenol, pindolol and propranolol, only pindolol strongly inhibited lipid peroxidation induced by xanthine oxidase-hypoxanthine in the presence of adenosine-5'-phosphate-Fe3+. In the reaction system, superoxide predominantly reduced iron because superoxide dismutase strongly prevented the iron reduction. However, pindolol had no effect on the superoxide-dependent iron reduction. Adding superoxide dismutase immediately stopped the lipid peroxidation, indicating that superoxide is closely connected with forming the initiator of xanthine oxidase-hypoxanthine-induced lipid peroxidation. On the other hand, pindolol also inhibited lipid peroxidation, whereas it did not react with superoxide, indicating that it inhibited xanthine oxidase-hypoxanthine-induced lipid peroxidation by an independent mechanism of superoxide. Pindolol sharply scavenged 2,2'-azino-bis-(3-ethylbenzothiazoline-6-sulfonate) radical cations, but the ability of pindolol to scavenge peroxyl radicals of 2,2'-azobis(2-amidinopropane)-dihydrochloride and 2,2'-diphenyl-p-picrylhydrazyl radicals was low. In addition, pindolol did not scavenge hydroxyl radicals at physiologically significant concentrations. These results suggest that the ability of pindolol to inhibit lipid peroxidation was due to scavenging carbon-centered radicals rather than peroxyl radicals.     

Antioxidant activity of isoacteoside from Clerodendron trichotomum

The antioxidant properties of isoacteoside, isolated from Clerodendron trichotomum (Verbenaceae), were investigated. This compound scavenged intracellular reactive oxygen species (ROS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, and prevented lipid peroxidation. This radical scavenging activity of isoacteoside protected cell viability of Chinese hamster lung fibroblast (V79-4) cells exposed to hydrogen peroxide (H2O2). Furthermore, isoacteoside reduced the apoptotic cells formation induced by H2O2, as demonstrated by the decreased number of sub-G1 hypo-diploid cells and apoptotic cell body formation. However, isoacteoside increased the activities of cellular antioxidant enzymes, superoxide dismutase (SOD) and catalase (CAT). Taken together, these findings suggest that isoacteoside, isolated from C. trichotomum, possesses antioxidant properties.     

汉防己甲素对大鼠肝保护和抗氧化作用研究

目的:使用汉防己甲素评价对四氯化碳诱导的大鼠肝损伤的保护作用以及抗氧化作用。方法:每日给予四氯化碳损伤大鼠不同的浓度汉防己甲素剂量分别为20,60,100mg/kg,随后检测血清和组织中谷胱甘肽(GSH),谷胱甘肽过氧化物酶,过氧化氢酶(CAT),超氧化和物歧化酶(SOD),谷胱甘肽S-转移酶(GST),脂质过氧化效应等指标,体外抗氧化使用使用超氧化物和过氧化物清除实验评价。结果:与对照组和四氯化碳模型组比较后发现,汉防己甲素在所用剂量下均显示出较为理想的肝保护和抗氧化效应。进一步的体外过氧化自由基清除和超氧化自由基清除实验表明,汉防己甲素较维生素C有更为优越的清除活性。结论:汉防己甲素能有效保护四氯化碳对大鼠造成的肝损伤,其保护机制可能与抗氧化和自由基清除密切相关。     

Withania somnifera (Ashwagandha) attenuates antioxidant defense in aged spinal cord and inhibits copper induced lipid peroxidation and protein oxidative modifications

Withania somnifera is classified in Ayurveda, the ancient Indian system of medicine, as a rasayana, a group of plant-derived drugs which promote physical and mental health, augment resistance of the body against disease and diverse adverse environmental factors, revitalize the body in debilitated conditions and increase longevity. We investigated the effects of Withania somnifera on copper-induced lipid peroxidation and antioxidant enzymes in aging spinal cord of Wistar rats. The activity of glutathione peroxidase (GPx) decreased significantly in the spinal cord from adult to aged mice. Treatment with Withania somnifera successfully attenuated GPx activity and inhibited lipid peroxidation in a dose dependent manner. Withania somnifera inhibited both the lipid peroxidation and protein oxidative modification induced by copper. These effects were similar to those of superoxide dismutase and mannitol. The results indicate the therapeutic potential of Withania somnifera in aging and copper-induced pathophysiological conditions.     

Lipid peroxidation of rat erythrocyte membrane induced by adriamycin-Fe3+.

Adriamycin-Fe3+ caused lipid peroxidation of erythrocyte membrane in relation to its concentration. Adriamycin-Fe3+ had a high affinity for membrane and the adriamycin-Fe(3+)-binding membranes membranes was also found to cause lipid peroxidation. Under aerobic conditions, adriamycin-Fe3+ caused a reduction of cytochrome c and ferrous iron formed spontaneously. Superoxide dismutase (EC 1.15.1.1) (SOD) strongly inhibited the reduction of cytochrome c; however, the enzyme promoted formation of ferrous iron independent of enzymatic action. These results suggest that cytochrome c was reduced by superoxide radical (O2-) or an adriamycin-iron-O2 complex such as adriamycin-Fe(3+)-O2-, but not by adriamycin-Fe2+. The ferrous iron chelator bathophenanthroline sulfonate (BPS) completely inhibited oxygen consumption caused by adriamycin-Fe3+, indicating that ferrous iron is absolutely required for the lipid peroxidation. SOD and hydroxyl radical scavengers did not inhibit the lipid peroxidation, indicating that O2- and hydroxyl radical were not involved in membrane peroxidation. The peroxidation reaction was dramatically inhibited by Tris buffer (2-amino-2-hydroxymethyl-1,3-propanediol). However, hydroxyl radical generation and lipid peroxidation in Tris buffer were not related obviously, indicating that Tris did not act as a hydroxyl radical scavenger. The initial rate of TBARS (thiobarbituric acid reactive substances) formation induced by a mixture of adriamycin-Fe3+ and adriamycin-Fe2+ was much faster than that induced by adriamycin-Fe2+ or adriamycin-Fe3+ alone. These results made it became possible to speculate that the lipid peroxidation might be initiated by an adriamycin-Fe(3+)-oxygen-adriamycin-Fe2+ complex.     

Antioxidant properties of Thonningianin A,isolated from the African medicinal herb,Thonningia sanguinea

The antioxidant properties of Thonningianin A (Th A), an ellagitannin, isolated from the methanolic extract of the African medicinal herb, Thonningia sanguinea were studied using the NADPH and Fe2+/ascorbate-induced lipid peroxidation (LPO), electron spin resonance spectrometer and the deoxyribose assay. Th A at 10 microM inhibited both the NADPH and Fe2+/ascorbate-induced LPO in rat liver microsomes by 60% without inhibitory effects on cytochrome P450 activity. Th A was similar to the synthetic antioxidant, tannic acid, as an inhibitor of both the NADPH and Fe2+/ascorbate-induced LPO but potent than gallic acid, vitamin C and vitamin E. While Th A poorly scavenged the hydroxyl radical generated by the Fenton reaction it dose-dependently scavenged 1,1-diphenyl-2-picrylhydrazyl, superoxide anion and peroxyl radicals with IC50 of 7.5, 10 and 30 microM, respectively. Furthermore, Th A showed inhibitory effects on the activity of xanthine oxidase with an IC50 of 30 microM. In the deoxyribose assay both T. sanguinea and its methanolic component Th A showed only site-specific (Fe3+ + H2O2) but not non-site-specific (Fe3+ + EDTA + H2O2) hydroxyl radical scavenging suggesting chelating ability for iron ions. Spectroscopic studies showed that Th A enhanced absorbance in the visible region in the presence of Fe2+ ions. These results indicate that the antioxidant properties of Th A involve radical scavenging, anti-superoxide formation and metal chelation.