Free radical scavenging and antioxidant activities of flavonoids extracted from the radix of Scutellaria baicalensis Georgi

Free radical scavenging and antioxidant activities of baicalein, baicalin, wogonin and wogonoside, the four major flavonoids in the radix of Scutellaria baicalensis Georgi, were examined in different systems. ESR results showed that baicalein and baicalin scavenged hydroxyl radical, DPPH radical and alkyl radical in a dose-dependent manner, while wogonin and wogonoside showed subtle or no effect on these radicals. Ten micromol/l of baicalein and baicalin effectively inhibited lipid peroxidation of rat brain cortex mitochondria induced by Fe(2+)-ascorbic acid, AAPH or NADPH, while wogonin and wogonoside showed significant effects only on NADPH-induced lipid peroxidation. In a study on cultured human neuroblastoma SH-SY5Y cells system, it was found that 10 micromol/l of baicalein and baicalin significantly protected cells against H(2)O(2)-induced injury. Baicalein was the most effective antioxidant among the four tested compounds in every system due to its o-tri-hydroxyl structure in the A ring. Compared with a well-known flavonoid, quercetin, the antioxidant activity of baicalein was lower in DPPH or AAPH system, but a little higher in those systems which might associate with iron ion. These results suggest that flavonoids in the radix of Scutellaria baicalensis with o-di-hydroxyl group in A the ring, such as baicalein and baicalin, could be good free radical scavengers and might be used to cure head injury associated with free radical assault.     

In vitro antioxidant and anti-diabetic analysis of Andrographis echioides and Andrographis paniculata ethanol extract

It is of interest to analyse and compare the antioxidant and anti-diabetic activity of ethanolic extracts of Andrographis echioides and Andrographis paniculata. Andrographis echioides and Andrographis paniculata were collected from a local farm. In vitro antioxidant activity was assessed by the potential of Piperine, Lupeol, beta sitosterol; DPPH free radical scavenging assay was performed by Liyana Pathirana and Shahidi method. In vitro anti-diabetic activity was assessed by alpha amylase inhibitory activity and alpha glucosidase inhibitory activity. The data were analysed by one-way-ANOVA to check the statistical significance among the groups and considered at the levels of p<0.05. Both the ethanolic extracts of Andrographis echioides and Andrographis paniculata showed significant antioxidant and anti-diabetic potential in a dose-dependent manner (100-500µg) and can be used as potential antidiabetic agents. Similar to antioxidant potential, Andrographis paniculata exhibited an increased anti-diabetic potential compared to Andrographis echioides. Data shows that the ethanolic extracts of Andrographis echioides and Andrographis paniculata possessed antioxidant and anti-diabetic activity and hence our present findings conclude that both plants can be considered for the development of natural drugs for the management of diabetes.     

Hepatoprotective and antioxidant property of Andrographis paniculata (Nees) in BHC induced liver damage in mice

Andrographis paniculata (AP) treatment prevents BHC induced increase in the activities of enzymes y-Glutamyl transpeptidase, glutathione-S-transferase and lipid peroxidation. The activities of antioxidant enzymes like superoxide dismutase, catalase, glutathione peroxidase and the levels of glutathione were decreased following BHC effect. Administration of AP showed protective effects in the activity of superoxide dismutase, catalase, glutathione peroxidase, glutathione reductase as well the level of glutathione. The activity of lipid peroxidase was also decreased. The result indicate antioxidant and hepatoprotective action of A. paniculata.     

Inhibition of free radical-induced peroxidation of rat liver microsomes by resveratrol and its analogues

Resveratrol (3,5,4'-trans-trihydroxystilbene) is a natural phytoalexin present in grapes and red wine, which possesses a variety of biological activities including antioxidative activity. To find more efficient antioxidants by structural modification, resveratrol analogues, that is, 3,4-dihydroxy-trans-stilbene (3,4-DHS), 4,4'-dihydroxy-trans-stilbene (4,4'-DHS), 4-hydroxy-trans-stilbene (4-HS) and 3,5-dihydroxy-trans-stilbene (3,5-DHS), were synthesized and their antioxidant activity studied for the free radical-induced peroxidation of rat liver microsomes in vitro. The peroxidation was initiated by either a water-soluble azo compound 2,2'-azobis(2-amidinopropane hydrochloride) (AAPH) or Fe(2+)/ascorbate, and monitored by oxygen uptake and formation of thiobarbituric acid reactive substances (TBARS). It was found that all of these trans-stilbene derivatives are effective antioxidants against both AAPH- and iron-induced peroxidation of rat liver microsomes with an activity sequence of 3,4-DHS>4,4'-DHS>resveratrol>4-HS>3,5-DHS. The remarkably higher antioxidant activity of 3,4-DHS is discussed.     

Iron chelation and related properties of Podophyllum hexandrum, a possible role in radioprotection

Aqueous extract of Podophyllum species has been reported to render significant protection against radiation induced mortality, cytogenetic damage and cell death. In view of this, present study was undertaken to investigate its antioxidant properties. Chelation, oxidation and reduction of Fe2+ and Fe3+ were measured using chelating agents 2-2' bipiridyl and potassium thiocyanate respectively. Podophyllum extract, in a dose dependent manner, chelated Fe2+ more efficiently than Fe3+ and also modulated Fe2+/Fe3+ ratio. Homogenate of mouse liver was used to measure TBARS for estimating lipid peroxidation. Podophyllum extract also inhibited lipid peroxidation in a dose dependent manner and maximum inhibition (92%) was achieved at 1000 micrograms/ml concentration. These results demonstrates that Podophyllum exhibits antioxidant properties as seen through chelation and modulation of redox state of iron ions and these may primarily contribute towards its radioprotective manifestation.     

Antioxidant activity of anthocyanin glycoside derivatives evaluated by the inhibition of liposome oxidation

Cyanidin-3-glycosides (arabinoside, rutinoside, galactoside and glucoside) and delphinidin-3-rutinoside were examined for their ability to inhibit lipid peroxidation induced either by Fe(II) ions, UV irradiation or 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH) peroxyl radicals in a liposomal membrane system. The antioxidant abilities of anthocyanins were compared with a water-soluble tocopherol derivative, trolox. The antioxidant efficacies of these compounds were evaluated by their ability to inhibit the fluorescence intensity decay of the extrinsic probe 3-[p-(6-phenyl)-1,3,5,-hexatrienyl] phenylpropionic acid, caused by the free radicals generated during peroxidation. All the anthocyanins tested (at concentrations of 15-20 microM) exhibited higher antioxidant activities against Fe(II)-induced peroxidation than UV- and AAPH-induced peroxidation, suggesting that metal chelation may play an important role in determining the antioxidant potency of these compounds. It was also found that delphinidin-3-rutinoside had a higher antioxidant activity against Fe(II)-induced liposome oxidation than cyanidin-3-rutinoside, which indicates an important role of the OH group in the B ring of delphinidin-3-rutinoside in its antioxidant action. The antioxidant activity of all the anthocyanins studied was higher than that of trolox in the case of Fe(II)-induced liposome oxidation and was comparable with the action of trolox in the case of UV- and AAPH-induced liposome membrane oxidation.     

Radiation protection by the ocimum flavonoids orientin and vicenin: mechanisms of action

In previous studies, flavonoids, orientin and vicenin, that were isolated from the leaf extract of Ocimum sanctum, were found to protect mice against radiation injury. Several flavonoids are known to be good antioxidants. Therefore, the effect of orientin and vicenin on radiation-induced lipid peroxidation in vivo and their antioxidant activity in vitro were studied. Adult mice were injected intraperitoneally with 50 microgram/kg of orientin or vicenin and exposed whole-body to 3 Gy of gamma radiation. Lipid peroxidation was measured in the liver 15 min to 8 h postirradiation. The antioxidant activity of orientin/vicenin (10-500 microM) was studied by measuring inhibition of hydroxyl radicals generated by the Fenton reaction (Fe(3+)-EDTA-ascorbic acid-H(2)O(2)) in vitro. The compounds were also tested for possible pro-oxidant and iron chelation activities at the above concentrations in the in vitro system. Orientin and vicenin provided almost equal protection against radiation-induced lipid peroxidation in mouse liver. Both compounds showed a significantly greater free radical-inhibiting activity in vitro than DMSO. Neither orientin nor vicenin showed any pro-oxidant activity at the concentrations tested. Both compounds inhibited free radical formation in the absence of EDTA. Free radical scavenging appears to be a likely mechanism of radiation protection by these flavonoids.     

Antioxidant properties and protective effects of a standardized extract of Hypericum perforatum on hydrogen peroxide-induced oxidative damage in PC12 cells

Free radical scavenging and antioxidant activities of a standardized extract of Hypericum perforatum (SHP) were examined for inhibition of lipid peroxidation, for hydroxyl radical scavenging activity and interaction with 1,1-diphenyl-2-picrylhydrazyl stable free radical (DPPH). Concentrations between 1 and 50 microg/ml of SHP effectively inhibited lipid peroxidation of rat brain cortex mitochondria induced by Fe2+/ascorbate or NADPH system. The results showed that SHP scavenged DPPH radical in a dose-dependent manner and also presented inhibitory effects on the activity of xanthine oxidase. In contrast, hydroxyl radical scavenging occurs at high doses. The protective effect of the standardized extract against H2O2-induced oxidative damage on the pheochromocytoma cell line PC 12 was investigated by measuring cell viability via 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT), lactate dehydrogenase (LDH) assays, caspase-3-enzyme activity and accumulation of reactive oxygen species [2',7'-dichlorofluorescin (DCF) assay]. Following 8-h cell exposure to H2O2 (300 microM), a marked reduction in cell survival was observed, which was significantly prevented by SHP (pre-incubated for 24 h) at 1-100 microg/ml. In a separate experiment, different concentrations of the standardized extract (0.1-100 microg/ml) also attenuated the increase in caspase-3 activity and suppressed the H2O2 -induced reactive oxygen species generation. Taken together, these results suggest that SHP shows relevant antioxidant activity both in vitro and in a cell system, by means of inhibiting free radical generation and lipid peroxidation.     

Resveratrol inhibition of lipid peroxidation

To define the molecular mechanism(s) of resveratrol inhibition of lipid peroxidation we have utilized model systems that allow us to study the different reactions involved in this complex process. Resveratrol proved (a) to inhibit more efficiently than either Trolox or ascorbate the Fe2+ catalyzed lipid hydroperoxide-dependent peroxidation of sonicated phosphatidylcholine liposomes; (b) to be less effective than Trolox in inhibiting lipid peroxidation initiated by the water soluble AAPH peroxyl radicals; (c) when exogenously added to liposomes, to be more potent than alpha-tocopherol and Trolox, in the inhibition of peroxidation initiated by the lipid soluble AMVN peroxyl radicals; (d) when incorporated within liposomes, to be a less potent chain-breaking antioxidant than alpha-tocopherol; (e) to be a weaker antiradical than alpha-tocopherol in the reduction of the stable radical DPPH*. Resveratrol reduced Fe3+ but its reduction rate was much slower than that observed in the presence of either ascorbate or Trolox. However, at the concentration inhibiting iron catalyzed lipid peroxidation, resveratrol did not significantly reduce Fe3+, contrary to ascorbate. In their complex, our data indicate that resveratrol inhibits lipid peroxidation mainly by scavenging lipid peroxyl radicals within the membrane, like alpha-tocopherol. Although it is less effective, its capacity of spontaneously entering the lipid environment confers on it great antioxidant potential.     

Synthesis and evaluation of 4-hydroxyphenylacetic acid amides and 4-hydroxycinnamamides as antioxidants

4-Hydroxyphenylacetic acid amides and 4-hydroxycinnamamides were synthesized and their antioxidant and neuroprotective activities were evaluated. Among the prepared compounds, 8b, and exhibited potent inhibition of lipid peroxidation in rat brain homogenates, and marked DPPH radical scavenging activities. Furthermore, and exhibited neuroprotective action against the oxidative damage induced by the exposure of primary cultured rat cortical cells to H(2)O(2), xanthine/xanthine oxidase, or Fe(2+)/ascorbic acid. Based on these results, we found that was the most potent antioxidant among the compounds tested.     

In vivo protection of synaptosomes by ferulic acid ethyl ester (FAEE) from oxidative stress mediated by 2,2-azobis(2-amidino-propane)dihydrochloride (AAPH) or Fe(2+)/H(2)O(2): insight into mechanisms of neuroprotection and relevance to oxidative stress-related neurodegenerative disorders

Ferulic acid ethyl ester (FAEE) is an ester derivative of ferulic acid, the latter known for its anti-inflammatory and antioxidant properties. Previous studies from our laboratory have shown that ferulic acid protects synaptosomal membrane system and neuronal cell culture systems against hydroxyl and peroxyl radical oxidation. FAEE is lipophilic and is able to penetrate lipid bilayer. Previous studies reported that FAEE reduces Alzheimer's amyloid beta peptide Abeta(1-42)-induced oxidative stress and cytotoxicity in neuronal cell culture by direct radical scavenging and by inducing certain antioxidant proteins. In the present study we tested the hypothesis that FAEE would provide neuroprotection against free radical oxidative stress in vivo. Synaptosomes were isolated from the gerbils that were previously injected intraperitoneally (i.p.) with FAEE or DMSO and were treated with oxidants, Fe(2+)/H(2)O(2) or 2,2-azobis(2-amidino-propane)dihydrochloride (AAPH). Synaptosomes isolated from the gerbil previously injected i.p. with FAEE and treated with Fe(2+)/H(2)O(2) and AAPH showed significant reduction in reactive oxygen species (ROS), levels of protein carbonyl, protein bound 4-hydroxynonenal (HNE, a lipid peroxidation product), and 3-nitrotyrosine (3-NT, another marker of protein oxidation formed by reaction of tyrosine residues with peroxynitrite) compared to Fe(2+)/H(2)O(2) or AAPH induced oxidative stress in synapotosomes isolated from the brain of gerbils that were previously injected with DMSO. The synaptosomes isolated from gerbil pre-injected with FAEE and subsequently treated with AAPH or Fe(2+)/H(2)O(2) showed induction of heme oxygenase (HO-1) and heat shock protein 70 (HSP-70) but reduced inducible nitric oxide synthase (iNOS) levels. These results are discussed with reference to potential use of this lipophilic antioxidant phenolic compound in the treatment of oxidative stress-related neurodegenerative disorders.     

Modulation of glutathione and antioxidant enzymes by Ocimum sanctum and its role in protection against radiation injury

Aqueous extract (OE) of the leaves of Ocimum sanctum, the Indian holy basil, has been found to protect mouse against radiation lethality and chromosome damage and to possess significant antioxidant activity in vitro. Therefore a study was conducted to see if OE protects against radiation induced lipid peroxidation in liver and to determine the role, if any, of the inherent antioxidant system in radioprotection by OE. Adult Swiss mice were injected intraperitoneally (i.p.) with 10 mg/kg of OE for 5 consecutive days and exposed to 4.5 Gy of gamma radiation 30 min after the last injection. Glutathione (GSH) and the antioxidant enzymes glutathione transferase (GST), reductase (GSRx), peroxidase (GSPx) and superoxide dismutase (SOD), as well as lipid peroxide (LPx) activity were estimated in the liver at 15 min, 30 min, 1, 2, 4 and 8 hr post-treatment. LPx was also studied after treatment with a single dose of 50 mg/kg of OE with/without irradiation. OE itself increased the GSH and enzymes significantly above normal levels whereas radiation significantly reduced all the values. The maximum decline was at 30-60 min for GSH and related enzymes and at 2 hr for SOD. Pretreatment with the extract checked the radiation induced depletion of GSH and all the enzymes and maintained their levels within or above the control range. Radiation significantly increased the lipid peroxidation rate, reaching a maximum value at 2 hr after exposure (approximately 3.5 times that of control). OE pretreatment significantly (P < 0.0001) reduced the lipid peroxidation and accelerated recovery to normal levels. The results indicate that Ocimum extract protects against radiation induced lipid peroxidation and that GSH and the antioxidant enzymes appear to have an important role in the protection.     

Effects of beta-carotene and alpha-tocopherol on radical-initiated peroxidation of microsomes.

Rat liver microsomal membranes were exposed to either beta-nicotinamide adenine dinucleotide phosphate (NADPH), adenosine 5'-diphosphate (ADP), and Fe+3 or to azocompounds, and the antioxidant activities of beta-carotene and alpha-tocopherol were studied. Lipid peroxidation was monitored either by malondialdehyde (MDA) formation in the thiobarbituric acid assay at 535 nm or by hydroperoxide formation at 234 nm, after high-pressure liquid chromatography (HPLC) separation of phospholipid hydroperoxides. The radical initiators, water-soluble 2,2'-azobis(2-amidinopropane) (AAPH) and lipid-soluble 2,2'-azobis(2,4-dimethylvaleronitrile (AMVN), when thermally decomposed at 37 degrees C under air, produced a constant rate of lipid peroxidation in microsomes and lag times inversely related to their concentrations. Using 25 mM AAPH, beta-carotene suppressed lipid peroxidation at a concentration of 50 nmol/mg protein; using 24 mM AMVN, an inhibition of MDA formation was observed at a concentration of only 5 nmol/mg protein. Inhibition by beta-carotene did not produce a clearly defined lag phase. During AAPH-induced lipid peroxidation, beta-carotene was consumed linearly, and high levels of the antioxidant were still present at the end of 45 min of incubation. Using NADPH/ADP/Fe+3, protection by beta-carotene was observed at 10 nmol/mg protein. alpha-Tocopherol effectively suppressed both MDA and hydroperoxide formation in a dose-dependent manner when either NADPH/ADP/Fe+3 or azocompounds were used. These effects were observed at very low concentrations of the added alpha-tocopherol, ranging from 2 to 3 nmol/mg protein. When the lag times were measurable (AAPH and AMVN), they were directly proportional to the concentration of alpha-tocopherol and revealed the presence of endogenous antioxidants in the microsomal membranes. Different temporal relationships between the loss of alpha-tocopherol and lipid peroxidation were observed in relation to the prooxidant used. A substantial depletion of about 70% of endogenous alpha-tocopherol preceded the propagation phase when induced by the azocompounds, while only 20% of antioxidant disappeared at the beginning of the peroxidation when induced by NADPH/ADP/Fe+3. Although our results show that both beta-carotene and alpha-tocopherol suppress the peroxidation of microsomal membranes, their antioxidant efficacy is influenced by several factors, including the type of radical initiator involved and the site and rate of radical production.     

Andrographis paniculata ameliorates carbon tetrachloride (CCl(4))-dependent hepatic damage and toxicity: diminution of oxidative stress

Andrographis paniculata (hempedu bumi) is a plant that possesses many medicinal values in treating several diseases and for health care maintenance. However, its hepatoprotective activity and mechanism of action have not been fully investigated. Therefore, this study aimed to evaluate the hepatoprotective effects of A. paniculata and its mechanism of action in rats. Carbon tetrachloride (CCl(4)) challenge of rats at a dose of 1.2 ml/kg body weight-induced oxidative stress in the liver. This was evidenced by augmentation in lipid peroxidation, which was accompanied by a decrease in the activities of antioxidant enzymes and depletion in the level of reduced glutathione (P < 0.05). Parrallel to these changes, CCl(4) challenge too, enhanced hepatic damage as evidenced by sharp increase in serum transaminases (e.g. alanine aminotransferase, aspartate aminotransferase, and lactate dehydrogenase) (P < 0.05). Additionally, the impairment of liver function corresponded to histolopathological changes. However, most of these changes were reversed in a dose-dependent fashion by pre-treatment of animals with A. paniculata (P < 0.05). The ability of A. paniculata to scavenge the 2,2-Diphenyl-2-picrylhydrazyl radical was determined through its EC(50) value. The EC(50) value of A. paniculata was 583.60 ± 4.25 μg/ml. In addition, A. paniculata was found to contain 65.37 ± 1.20 mg/g total phenolics expressed as gallic acid equivalent. From these studies, it is concluded that A. paniculata could be used as a hepatoprotective agent and possesses the potential to treat or prevent degenerative diseases where oxidative stress is implicated.     

Novel and potent biological antioxidants on membrane phospholipid peroxidation: 2-hydroxy estrone and 2-hydroxy estradiol

Catechol estrogens, 2-hydroxy estrone, 2-hydroxy estradiol and 2-hydroxy estriol, were tested as possible antioxidants of phospholipid peroxidation induced by Fe3+-ADP-adriamycin, using phospholipid liposomes as lipid source and alpha-tocopherol or other steroids as reference compounds. The parameters of antioxidant activities were: elongation of induction period, inhibition of O2 consumption required for lipid peroxidation and inhibition of peroxidative cleavage of unsaturated phospholipid. Of the tested compounds, 2-hydroxy estradiol or 2-hydroxy estrone had more potent activity than that of tocopherol.     

Antiulcer activity of Andrographis paniculata (Burm.f.) wall. against cysteamine-induced duodenal ulcer in rats

Antiulcer activity of Andrographis paniculata was evaluated by cysteamine induced duodenal ulcer model in rats. Male albino Wistar rats were pre-administered with 200 mg/kg body wt. of hydroalcoholic extact of Andrographis paniculata (HAEAP) orally, for 30 days prior to i.p. administration of 420 mg/kg body wt. of cysteamine as a single dose. Rats preadministered with 30 mg/kg body wt. of ranitidine served as standard drug. Ulcer index, thiobarbituric acid reactive substances, mucin, glutathione peroxidase and myeloperoxidase activities, reduced glutathione/oxidized glutathione (GSH/GSSG) ratio, glycoproteins and membrane bound enzyme activities were measured in duodenum of experimental animals. The ulcer score and myeloperoxidase activity were significantly minimized in rats treated with HAEAP. Mucin content was found to be preserved in rats treated with the extract. GSH/GSSG ratio and glutathione peroxidase activities were found to be maintained by the HAEAP. Level of lipid peroxidation products was found to be significantly low in HAEAP treated rats compared to ulcer control rats. The basolateral and brush border membrane bound enzyme activities which were depleted significantly in ulcer control rats were found to be maintained in rats pre-treated with the extract. The ulcer preventing effect was comparable to that of ranitidine treated rats. Level of glycoproteins was also found to be preserved in rats treated with the extract. The normal rats treated with the HAEAP did not show any abnormal alterations in the parameters studied. Histopathological observations also showed the ulcer preventing effect of the HAEAP. It is suggested that the ulcer preventing effect may be due to its mucin preserving and antioxidant nature.     

Synthesis of andrographolide derivatives: a new family of alpha-glucosidase inhibitors

Andrographolide (1), the cytotoxic agent of the plant Andrographis paniculata, was subjected to semi-synthetic studies leading to a series of new derivatives, a novel family of glucosidase inhibitors. Nicotination of 3,19-hydroxyls in 15-alkylidene andrographolide derivatives (9) was favorable to alpha-glucosidase inhibition activity. Among them, 15-p-chlorobenzylidene-14-deoxy-11,12-didehydro-3,19-dinicotinateandrographolide (11c) was a very potent inhibitor against alpha-glucosidase with an IC50 value of 6 microM. However, all compounds concerned for beta-glucosidase showed no inhibition. All compounds synthesized were characterized by the analysis of NMR, IR, HRMS spectra and the stereochemistry of 2 was confirmed by X-ray analysis.     

Antioxidant Activities of Some Extracts of Thymus zygis

The antioxidant activities of methanol and ethyl ether extracts obtained from Thymus zygis, collected during the flowering or non-flowering period, were evaluated and compared. To investigate this potential, extracts were tested on their capacity to react with diphenyl-picrylhydrazyl (DPPH) in a homogeneous medium, and to inhibit Fe²⁺/ascorbate-induced membrane lipid peroxidation, as estimated by the formation of thiobar-bituric acid-reactive substances (TBARS). Although methanol extracts reduce DPPH radicals more efficiently than ethyl ether extracts, suggesting a potent radical scavenger activity, the ethyl ether extracts were found to be most active in inhibiting lipid peroxidation in sarcoplasmic reticulum (SR) membranes. In addition, both extracts present peroxyl and superoxide radical scavenging activities. Peroxyl radicals were generated by the water soluble 2, 2A-azobis(2-amidinopropane) dihydrochloride (AAPH) azoinitiator, and the scavenging activities of the extracts were measured by the inhibition of cis-parinaric acid (PnA) fluorescence decay in SR. Superoxide radicals were generated either by an enzymatic or a non-enzymatic system, and the scavenger ability was evaluated by the inhibition of nitrob-lue tetrazolium reduction. Methanolic extracts are more potent as scavengers of peroxyl and super oxide radicals than the ethyl ether extracts. Apparently, there is a relationship between antioxidant potency and the total phenolic groups content in each extract.     

beta-Carotene: interactions with alpha-tocopherol and ascorbic acid in microsomal lipid peroxidation

beta-Carotene, alpha-tocopherol, and ascorbic acid were tested for their ability to inhibit, enhance, or react synergistically with O(2) (15, 150, 760 torr) and, 2,2'-azobis (2-amidino-propane) dihydrochloride (AAPH) or 1,1'-azobis (cyclohexane-carbonitrile) (ACCN) in isolated rat liver microsomes. beta-Carotene did not protect against lipid peroxidation, i.e., malondialdehyde (MDA) formation, in microsomal samples incubated at 37 degrees C with aqueous soluble AAPH at all added beta-carotene concentrations and oxygen tensions. More MDA (16%, p < 0.001) was produced at 15 torr of O(2,) and 160 nmol/mg protein of beta-carotene compared to respective vehicle control. Individually, alpha-tocopherol and ascorbic acid exhibited antioxidant protection (ascorbic acid &z.Gt; alpha-tocopherol); however, a mixture of both compounds was no more protective than ascorbic acid alone. beta-Carotene demonstrated a concentration-dependent antioxidant affect at 15 torr O(2) (p < 0.01); but a prooxidant effect at higher O(2) at 150 and 760 torr (>57%, p < 0.001) by lipid-soluble ACCN. alpha-Tocopherol exhibited concentration-dependent inhibitory effects on microsomal MDA formation at all oxygen tensions, but was most effective under 150 torr. Ascorbic acid demonstrated a concentration-dependent antioxidant effect only at 150 torr. ACCN-induced lipid peroxidation was no greater for the combination of the three compounds than ascorbic acid added alone. Thus, antioxidant or prooxidant activities for beta-carotene, alpha-tocopherol, and ascorbic acid in microsomal suspensions are related to O(2) tension, solubility, antioxidant concentrations and are governed by complex interactions. Differences between AAPH- and ACCN-induced lipid peroxidation are related to differences in lipid solubility.     

Protective effect of butin against hydrogen peroxide-induced apoptosis by scavenging reactive oxygen species and activating antioxidant enzymes

The antioxidant property of butin was investigated for cytoprotective effect against H(2)O(2)-induced cell damage. This compound showed intracellular reactive oxygen species (ROS) scavenging, 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging, inhibition of lipid peroxidation, and DNA damage. This radical scavenging activity of butin protected cell damage exposed to H(2)O(2). Also, butin reduced the apoptotic cells induced by H(2)O(2), as demonstrated by the decreased DNA fragmentation, apoptotic body formation, and caspase 3 activity. In addition, butin restored the activity and protein expression of cellular antioxidant enzymes, superoxide dismutase (SOD), and catalase (CAT) in H(2)O(2)-treated cells. Taken together, these findings suggest that butin protected cells against H(2)O(2)-induced cell damage via antioxidant property.