Reduction of myocardial infarct size in rabbits by a novel indole derivative with antioxidant and free radical scavenging properties

ESR detection of ROS generated by TiO2 coated with fluoridated apatite

Specific materials used in the manufacture of dentures may enhance the removal of micro-organisms. The ultraviolet A (UVA) irradiation of acrylic resin containing titanium dioxide (TiO(2)) generates reactive oxygen species (ROS) by photocatalysis that shows antibacterial effects. In this study, we tested the hypothesis that TiO(2) coated with fluoridated apatite (FAp-TiO(2)) can generate ROS via photo-catalysis by using electron spin resonance (ESR), and that acrylic resin containing FAp-TiO(2) can show antifungal properties by measuring the viability of Candida albicans. We demonstrated that hydroxyl radicals (HO(*)) were generated through excitation of TiO(2), TiO(2) coated with apatite (HAp-TiO(2)), and FAp-TiO(2). The HO(*) generation through excitation of FAp-TiO(2) was higher than that of TiO(2) and HAp-TiO(2). Regarding antifungal activity, cell viability on acrylic resin containing FAp-TiO(2) was lower than that of TiO(2) and HAp-TiO(2). FAp-TiO(2) showed superior photocatalytic effects, and these characteristics may lead to novel methods for the clinical application of denture-cleaning treatments.

Design and synthesis of nitrate esters of aromatic heterocyclic compounds as pharmacological preconditioning agents

Ischemic preconditioning (IPC) constitutes an endogenous protective mechanism in which one or more brief periods of myocardial ischemia and reperfusion render the myocardium resistant to a subsequent more-sustained ischemic insult. Pharmacological preconditioning represents an ideal alternative of IPC. We now describe the design and synthesis of indole, quinoline, and purine systems with an attached pharmacophoric nitrate ester group. The indole and quinoline derivatives 4 and 5 possess structural features of the nitrate containing K(ATP) channel openers. Purine analogues 11 and 12, substituted at the position 6 by a piperidine moiety and at position 9 by an alkyl nitrate, could combine the effects of the nitrate containing K(ATP) channel openers and those of adenosine. Compound 13 bears the nicotinamide moiety of nicorandil instead of nitrate ester. Compounds 4, 5, and 11 reduced infarction and the levels of malondialdehyde (MDA) at reperfusion in anesthetized rabbits. Compounds 12 and 13 did not significantly reduce the infarct size. Analogues 4 and 5 increased cGMP and MDA during ischemia, while combined analogue 4 and mitoK(ATP) blocker 5-hydroxydecanoic acid (5-HD) abrogated this benefit suggesting an action through mitoK(ATP) channel opening. Treatment with derivative 11 combined with 5-HD as well as treatment with 11 and adenosine receptor blocker 8-(p-sulfophenyl)theophylline (SPT) did not abrogate cardioprotection. Compound 11 is a lead molecule for the synthesis of novel analogues possessing a dual mode of action through cGMP-mitoK(ATP) channel opening-free radicals and through adenosine receptors.

Malondialdehyde as an indicator of oxidative stress during abdominal aortic aneurysm repair

Ischemia-reperfusion injury significantly contributes to abdominal aortic aneurysm (AAA)- related mortality and morbidity; therefore, we measured oxidative stress during open AAA repair and investigated any potential associations with intraoperative or perioperative events (aortic clamping time, blood loss, and the need to transfer to the intensive care unit). Blood samples were collected at specific time points from 53 patients undergoing open AAA repair: (1) before induction of anesthesia; (2) 15, 30, 60, and 120 minutes after aortic clamping; (3) 15 and 60 minutes after clamp removal; and (4) 24 hours postoperatively. Malondialdehyde (MDA) levels were measured by a spectrophotometric method. Baseline MDA values in patients with AAA were significantly higher than in controls (P < .0001). A positive correlation was found between preoperative MDA levels and the size of AAAs (Pearson correlation = 0.578, P < .001). No difference was observed in MDA levels between ruptured and nonruptured AAAs; however, when all symptomatic patients (ruptured and elective symptomatic AAAs, n = 18) were considered, there was a significant elevation in MDA levels (P < .001). There was also a significant increase in MDA values in patients transferred postoperatively to the intensive care unit (P < .001). Finally, a positive association was found between the duration of aortic clamping with MDA values at 15 and 60 minutes after declamping, but not after 24 hours (Pearson correlation = 0.467, P < .001). MDA levels may predict the postoperative course of elective and ruptured AAAs.

Effects of mannitol in the prevention of lipid peroxidation during liver resection with hepatic vascular exclusion

STUDY OBJECTIVE

To examine the efficacy of mannitol in the prevention of lipid peroxidation during major liver resections performed during hepatic inflow occlusion.

DESIGN

Prospective, randomized, open-label study.

SETTING

Aretaieion Hospital, a university-affiliated hospital.

PATIENTS

30 ASA physical status II and III patients, less than 75 years of age, scheduled for elective liver resection.

INTERVENTIONS

All patients received combined general and epidural anesthesia. Laparotomy was performed through a bilateral subcostal incision, and hepatectomy was performed by inflow vascular exclusion (Pringle's maneuver). Before this maneuver, and if the patients were hemodynamically stable, they were randomized to receive either mannitol 20% 1.5 mL kg(-1) (group M) or normal saline 1.5 mL kg(-1) (group S) intravenously for 30 minutes.

MEASUREMENTS

Venous blood malondialdehyde (MDA) concentration, as an index of lipid peroxidation, was measured spectrophotometrically at selected time points.

MAIN RESULTS

Patients in both groups presented with raised MDA values (P < 0.05) for the period starting before the release of vascular occlusion until 6 days postoperatively. In patients receiving mannitol, lower MDA values were observed (P < 0.05) compared with group S at the end of operation.

CONCLUSION

Mannitol has an antioxidant activity, but we were unable to confirm a positive impact on the postoperative clinical course.

Application of NMR-based metabonomics in the investigation of myocardial ischemia-reperfusion, ischemic preconditioning and antioxidant intervention in rabbits

NMR based metabonomics was applied in rabbit plasma samples during myocardial ischemia-reperfusion injury, with the following interventions: (1) Control (no intervention); (2) ischemic preconditioning (IpC); (3) administration of melatonin; (4) IpC+administration of melatonin; (5) treatment of the indole derivative C6458. The (1)H NMR signal intensity ratio of lactate/glucose was found to increase in Control samples during reperfusion compared to baseline, while lactate+alanine/acetate was decreased suggesting impairment of aerobic glycolysis and concomitant lipid utilization. In contrast, after IpC or treatment with C6458, the lactate/glucose ratio was similar to baseline in accordance with the previously reported decrease in infarct size. Multivariate statistical methods such as Principal Component Analysis (PCA), and Discriminant Analysis (DA) were used for the discrimination of samples. The use of ANOVA variable preselection prior to PCA was advantageous in producing adequate models. PCA could classify the Control group in three clusters according to the condition of the heart (baseline-ischemia-reperfusion) while in the IpC groups no classification was evident. PCA discrimination upon treatment with melatonin and C6458 provided further evidence of their effect on the metabolic profile. The supervised DA resulted in fine discrimination between the different subgroups. Plasma NMR spectra in combination with pattern recognition techniques proved to be an efficient and simple method to depict the metabolic changes produced upon ischemia-reperfusion of the myocardium.

Divergent effects of rofecoxib on endothelial function and inflammation in acute coronary syndromes

BACKGROUND

The safe use of selective inhibitors of cyclooxygenase-2 in patients with cardiovascular disease has been questioned because of studies showing an increased risk of cardiac events. We examined the short-term effect of rofecoxib, a selective cyclooxygenase-2 inhibitor, on endothelial function, oxidative damage and inflammation in patients with acute coronary syndromes without ST-segment elevation.

METHODS

Forty-three patients with acute coronary syndromes without ST-segment elevation participated in the study. Flow-mediated dilatation (FMD), nitrate-mediated dilatation (NMD) of the brachial artery, malondialdehyde, a marker of lipid peroxidation, C-reactive protein, an acute phase marker of inflammation, and interleukin-6, a proinflammatory cytokine, were measured within 24 h of admission and a week later. Patients were randomized to receive for a week 100 mg aspirin daily with either 25 mg of rofecoxib (n=21) or placebo (n=22) orally once daily.

RESULTS

Malondialdehyde, C-reactive protein and interleukin-6 levels were reduced in the rofecoxib group (p=0.04, p=0.003 and p=0.02 respectively) while they remained unchanged in the placebo group after 1 week of treatment. FMD and NMD changes in both groups were not statistically different.

CONCLUSIONS

Co-administration of rofecoxib with low-dose aspirin decreases inflammatory and oxidative indices but does not improve endothelial function. The lack of improvement in FMD despite the improvement in inflammation and oxidative stress could be viewed in association to the recent observations on the adverse effects of COX-2 inhibition on the cardiovascular system.

The olive constituent oleuropein exhibits anti-ischemic, antioxidative, and hypolipidemic effects in anesthetized rabbits

Thgoal of this study was to evaluate the efficacy of the antioxidant olive constituent, oleuropein, on infarct size, oxidative damage, and the metabolic profile in rabbits subjected to ischemia. Oleuropein, 10 or 20 mg/(kg x d), was administered to 8 groups that consumed a normal or hypercholesterolemic diet for 6 wk or only the higher dose for 3 wk. Circulating levels of malondialdehyde, protein carbonyl, nitrite+nitrate, cholesterol, triglycerides, SOD activity, and the metabolic profile were measured using 1H NMR spectra. In rabbits that consumed the normal diet, the infarct size (percentage of infarct to risk areas) was reduced by the administration of 10 mg oleuropein/(kg x d) (16.1 +/- 2.9%) or 20 mg oleuropein/(kg x d) for 3 wk (21.7 +/- 2.2%) or for 6 wk (24.3 +/- 1.3%) compared with the control group (48.05 +/- 2.0%, P < 0.05). Only the higher dose of 20 mg/(kg x d) reduced the infarct size in hypercholesterolemic rabbits (34.7 +/- 4.4% for 6 wk and 34.8 +/- 6.1% for 3 wk) compared with the cholesterol-fed control group (52.8 +/- 2.4%, P < 0.05). Oleuropein decreased the plasma lipid peroxidation product and protein carbonyl concentrations compared with the control groups, in which these factors increased relative to baseline due to ischemia and reperfusion. Furthermore, in rabbits administered oleuropein, RBC superoxide dismutase activity did not change during ischemia and reperfusion. This activity was significantly higher than in both control groups in which it was reduced by ischemia and reperfusion compared with baseline. Treatment for 6 wk with both doses of oleuropein reduced total cholesterol and triglyceride concentrations. 1H NMR spectra revealed a different profile of glycolysis metabolites in the oleuropein-treated groups compared with the controls. Oleuropein, for 3 or 6 wk, reduced the infarct size, conferred strong antioxidant protection and reduced the circulating lipids. This is the first experimental study in vivo that suggests the possibility of using an olive constituent in the treatment of ischemia.

Acute Effect of Black and Green Tea on Aortic Stiffness and Wave Reflections

OBJECTIVE

While most studies have shown an inverse relation between tea consumption and cardiovascular risk, other studies have shown opposite results. Aortic stiffness and wave reflections are markers of cardiovascular disease and prognosticators of cardiovascular risk.

METHODS

The acute effect of black and green tea on aortic stiffness and wave reflections was assessed in 29 healthy volunteers in a randomized, single-blind, sham-procedure controlled, cross-over design. In the black tea sub-study, 16 subjects received 6 gm of tea, caffeine (175 mg), or hot water in 3 different sessions. In the green tea sub-study, 13 subjects received 6 gm of tea, caffeine (125 mg), or hot water. Carotid-femoral pulse wave velocity and wave reflection indices were measured at baseline and for 3 hours after consumption.

RESULTS

Black tea increased pulse wave velocity during the first 90 min (increase by 0.49 m/sec, P < 0.05), showing a rapid return towards baseline values thereafter (P = 0.07 for the whole study period); in contrast, green tea had no effect. Both black and green tea increased augmentation index (by 5.0% and by 6.6%, P < 0.01 and P < 0.001, respectively) throughout the study. These changes were less than the respective changes produced by caffeine. Both black and green tea had a significant pressor effect. No change in oxidant status was found with both types of tea.

CONCLUSIONS

Both black and green tea increases acutely wave reflections and only black tea increases aortic stiffness. Tea flavonoids may play a role in the attenuation of the effects of caffeine contained in tea.

The Ca2+-sensitizer levosimendan improves oxidative damage, BNP and pro-inflammatory cytokine levels in patients with advanced decompensated heart failure in comparison to dobutamine

AIM

To investigate the effect of a new inotropic drug, levosimendan compared with dobutamine on levels of brain natriuretic peptide (BNP), interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-alpha), and malondialdehyde (MDA) in patients with severe decompensated heart failure.

METHODS AND RESULTS

Twenty-nine consecutive patients (22 males and 7 females), mean age 70.5+/-9.9 years, with decompensated heart failure on standard medical therapy, were randomised to receive either a 24 h infusion of levosimendan (n=15) or dobutamine (n=14). Blood samples were drawn at baseline, 48 h and 5 days post infusion. Levosimendan produced a significant reduction in BNP compared to baseline, at both 48 h (744.1+/-100 vs 1136.3+/-93.7 pg/ml, p=0.04) and 5 days (446+/-119.3 vs 1136.3+/-93.7 pg/ml, p=0.03), while IL-6 values decreased after 5 days (4.8+/-1.3 vs 8.6+/-1.5 pg/ml, p=0.01). MDA levels were significantly lower 5 days after levosimendan compared to baseline (2.3+/-0.2 vs 3+/-0.3 microM, p=0.01). TNF-alpha levels did not differ between the groups. The comparison of percentage alteration compared to baseline showed that BNP (-44.5+/-7.6% vs 4.8+/-18.7%, p=0.025), MDA (-21.8+/-5.1% vs 14.9+/-8.5%, p=0.001) and IL-6 (-38.8+/-12.5% vs 70.2+/-24%, p=0.001) levels were significantly lower in the levosimendan group 5 days after treatment compared to the dobutamine group.

CONCLUSIONS

Treatment with levosimendan in advanced decompensated heart failure exerts a beneficial hemodynamic, anti-inflammatory and antioxidant effect. These findings may give an insight into the favourable impact on mortality that levosimendan appears to have in published multicenter trials.

Rapid effect of pravastatin on endothelial function and lipid peroxidation in unstable angina

BACKGROUND

Oxidative stress contributes to endothelial dysfunction, an important step to the pathogenesis of atherosclerosis and coronary events. Latest studies revealed the existence of pleiotropic and especially antioxidant properties of statins. We sought to examine the effects of pravastatin on lipid peroxidation and endothelial function, independently from lipid-lowering, in patients with unstable angina (UA).

METHODS

Thirty-seven patients (males), 64.46+/-9.09 years, suffering from UA enrolled in the study. Patients were not on statin medication before admission and they received after randomization either 40 mg pravastatin daily (group A, n = 20), or placebo (group B, n = 17). Malondialdehyde (MDA) concentration, an index of lipid peroxidation and plaque instability, flow-mediated dilatation (FMD) of the brachial artery and blood lipids were measured on the second day of hospitalization and 10 days later.

RESULTS

MDA decreased significantly in both groups (A, p = 0.008; B, p = 0.003). FMD increased significantly in group A (p = 0.007), whereas in group B it did not change. Serum lipids remained unaltered in all three groups.

CONCLUSIONS

Pravastatin administration improved FMD within 10 days and this favorable effect occurred before any significant reduction in blood lipids, revealing its pleiotropic effects during the early phase of an acute coronary syndrome. Circulating lipid peroxidation products in patients with UA decreased significantly during the same period independently of endothelial function and pravastatin therapy.

Relationship between iNOS expression and aortic cell proliferation and apoptosis in an elastase-induced model of aorta aneurysm and the effect of 1400 W administration

BACKGROUND

In the present study, we employed an elastase infusion-dependent abdominal aortic aneurysm (AAA) model to examine inducible nitric oxide synthase (iNOS) expression in relation to cellular proliferation and apoptosis in this pathologic condition. Furthermore, we employed N-(3-(aminomethyl)benzyl)acetamidine (1400 W), a previously shown selective iNOS inhibitor, to further explore this relationship.

METHODS

Adult male Wistar rats were randomized into separate groups. Group A served as a control and received an intra-aortic saline infusion, while groups B, C, and D received an intra-aortic elastase infusion according to standard protocols. The animals in group C were administered postoperatively the highly selective iNOS inhibitor, 1400 W, while rats in group D received regularly the same compound preoperatively and postoperatively. The animals were killed at postoperative days 7 and 14. Aorta diameter and nitric oxide (NO), nitrite/nitrate, and MDA levels were measured. iNOS expression was assessed by immunohistochemistry and Western blot analysis, while Ki-67 immunohistochemistry and TUNEL assay were used to evaluate cellular proliferation and apoptosis, respectively.

RESULTS

Increased iNOS and NO levels accompanied aneurysm development in groups B, C, and D, but these levels were significantly lower in groups C and D, compared with group B. Interestingly, very low but detectable levels of iNOS were found in the control group, indicating a basal constitutive level. Cell growth parameters were augmented in group B compared with group A. In contrast, groups C and D exhibited a significant decrease of the cellular growth parameters but did not attain normal values.

CONCLUSIONS

iNOS-derived NO is associated with the cellular growth parameters of the vessel cells, predominantly smooth muscle cells. Selective iNOS blockage ameliorates the cellular remodeling in AAAs.

In vitro scavenging activity for reactive oxygen and nitrogen species by nonsteroidal anti-inflammatory indole, pyrrole, and oxazole derivative drugs

This study was undertaken to evaluate the scavenging activity for reactive oxygen species (ROS) and reactive nitrogen species (RNS) by several nonsteroidal anti-inflammatory drugs (NSAIDs), namely indole derivatives (indomethacin, acemetacin, etodolac), pyrrole derivatives (tolmetin and ketorolac), and an oxazole derivative (oxaprozin). The inhibition of prostaglandin synthesis constitutes the primary mechanism of the anti-inflammatory action of these drugs. Nevertheless, it has been suggested that the anti-inflammatory activity of NSAIDs may be also partly due to their ability to scavenge ROS and RNS and to inhibit the respiratory burst of neutrophils triggered by various activator agents. Thus, the scavenging activity of these NSAIDs was evaluated against an array of ROS (O(2)(-), HO, HOCl, and ROO) and RNS (NO and ONOO(-)) using noncellular in vitro systems. The results obtained demonstrated that tolmetin, ketorolac, and oxaprozin were not active against O(2)(-), while acemetacin, indomethacin, and etodolac exhibited concentration-dependent effects. Oxaprozin was also the least active scavenger for HO, among all the tested NSAIDs shown to be active. The scavenging effect for HOCl was not observed for any of the tested NSAIDs. The ROO was effectively scavenged by etodolac, with the other tested NSAIDs being much less active. NO and ONOO(-) were scavenged by all the tested NSAIDs. These effects may strongly contribute to the anti-inflammatory therapy benefits that may be attained with some of the studied NSAIDs.

Melatonin does not prevent the protection of ischemic preconditioning in vivo despite its antioxidant effect against oxidative stress

Free radicals are involved in the protective mechanism of preconditioning (PC), whereas antioxidant compounds abolish this benefit. Melatonin is a hormone with antioxidant properties. The aim of our study was to evaluate the effect of melatonin on infarct size in ischemic preconditioning in vivo. We randomly divided 33 male rabbits into four groups and subjected them to 30 min of myocardial ischemia and 3 h of reperfusion with the following prior interventions: (i) no intervention, (ii) iv melatonin at a total dose of 50 mg/kg, (iii) PC with two cycles of 5 min ischemia and 10 min reperfusion, and (iv) combined melatonin and PC. In a second series of experiments, another antioxidant agent N-acetylcysteine (NAC) was used in a control and in a PC group. Myocardial infarct size was determined and blood samples were drawn at different time points for the determination of lipid peroxidation products, total superoxide dismutase (SOD) activity, and (1)H-NMR spectra to evaluate the changes in the metabolic profile. Melatonin showed no effect on myocardial infarct size in the group of sustained ischemia (42.9 +/- 3.6% vs 47.4 +/- 4.9%) and it did not attenuate the reduction of myocardial infarct size in the PC group (13.6 +/- 2.4% vs 14.0 +/- 1.7%). A similar effect was found in NAC-treated groups (44.8 +/- 3.4% vs 14.3 +/- 1.3%). Lipid peroxidation product levels were significantly elevated in the control and PC groups, whereas melatonin decreased them in both groups. The SOD activity was enhanced in the PC group compared to controls; melatonin kept SOD activity unchanged during ischemia/reperfusion and enhanced its activity when it was combined with PC. Melatonin did not change the metabolic profile of the control and PC groups. Melatonin does not prevent the beneficial effect of ischemic PC on infarct size despite its antioxidant properties.

Histological and lipid peroxidation changes after administration of 2-acetylaminofluorene in a rat liver injury model following selective periportal and pericentral damage

Administration of 2-acetylaminofluorene (2-AAF) suppresses mature hepatocyte proliferation following selective periportal or pericentral damage induced by allyl-alcohol (AA) or carbon tetrachloride (CCl(4)) administration, respectively. The aim of the present study was to investigate the histological and the lipid peroxidation changes after 2-AAF administration following CCl(4) and AA treatment. The study comprised 108 male Wistar rats that were assigned in four groups: Group A: a placebo pellet was implanted in their neck and on 7th day single dosages of AA and CCl(4) were administrated. Group B: 28-day release 2-AAF pellets (7 0mg-2.5mg per day) were implanted on the neck and on 7th day received a single dose of CCl(4). Group C: 28-day release 2-AAF pellets (70-2.5mg per day) were implanted on the neck and on 7th day a single dose of AA and CCl(4) were administrated. Group D: Sham-operated. Rats of each group were sacrificed on the 9th, 11th, 13th and 21st day. Liver tissue was obtained for histological examination and blood was collected for lipid peroxidation evaluation by measuring malondialdehyde (MDA) and for liver enzymes. On the 9th and 21st day the histological score of liver necrosis was statistically higher on Groups B and C compared to Group A. Concentration of MDA in Group A was significantly higher than in Groups B and C on 9th and 11th days. Transaminase levels, however, were significantly higher in Group A on 9th day compare to the Groups B and C. In conclusion, it appears that oxidative stress was correlated with liver necrosis and with liver regeneration. Suppression of liver regeneration after 2-AAF administration leads to lower malondialdehyde concentrations.

Interactions of a series of novel spiropyranocoumarin derivatives with reactive oxygen species

A series of new spiro-substituted pyranocoumarin derivatives have been synthesized starting from the commercially available 7-hydroxycoumarin and the conformation of the pyran ring was investigated. The antioxidant activity of the compounds was evaluated in-vitro, by means of three different tests: the interaction with the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH), the competition with DMSO for hydroxyl radicals scavenging ability and the quenching of superoxide anions generated by the enzymic xanthine-xanthine oxidase system. In the DPPH test the spiroadamantane derivative 13 was the most active and possessed a 40% inhibition at a concentration of 400 microM. All compounds successfully compete with DMSO for hydroxyl radicals generated by the Fe(3+)/ascorbic acid system. Compound 13 inhibited the oxidation of DMSO (3.125 mM) by 93% at 2 mM and by 71% at 0.25 mM. The corresponding second-order rate constants have been estimated and all compounds demonstrated higher rate constants compared with the reference compounds, 7-hydroxycoumarin and mannitol. Derivatives possessing extended conjugation showed the highest inhibitory activity for superoxide anions generated by the xanthine-xanthine oxidase system, although the results of this experiment possessed partial parallelism with the results observed in the other two tests. The overall obtained data indicate that the size of the different spiro- substituents influence the degree of free radical scavenging and demonstrate the importance of extended conjugation for the antioxidant activity. Due to its multiple mechanism of protective action, derivative 13 may serve as a lead for the development of analogues that could be useful for the treatment of pathophysiological processes dependent upon reactive oxygen species.

Synthesis, conformational analysis and free radical scavenging activity of some new spiropyranoquinolinones

A series of novel spiroadamantyl- and spirocyclical substituted pyranoquinolin-2-ones were synthesized and the conformation of the pyran ring was investigated. The free radical scavenging activity of the synthesized compounds was determined by their interaction with the stable free radical 1,1-diphenyl-2-picrylhydrazyl (DPPH). All compounds tested scavenged the DPPH radical and among them derivatives possessing extended conjugation showed the highest activity.

Reactions of Indole Derivatives with Cardioprotective Activity with Reactive Oxygen Species. Comparison with Melatonin

We have previously reported on the synthesis of novel indole derivatives containing an amine-triazole moiety (1a-d, 2a-c), and their antioxidant activity on in vitro non-enzymatic rat hepatic microsomal lipid peroxidation. Some of the compounds showed protective activity against oxidative injury of ischemic myocardium. In the present paper we investigated the interactions of these derivatives with reactive oxygen species, in order to find a mechanism of their antioxidant capacity and to identify structural characteristics responsible for these properties. These interactions were compared with melatonin, which is also an indole derivative. The antioxidant profiles of the compounds were established by different in vitro protocols as follows: 1) by the interaction of the compounds with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) stable free radical, 2) their scavenging effects on superoxide anions using an enzymic system of xanthine-xanthine oxidase, 3) their inhibitory effects on xanthine oxidase and 4) their ability to scavenge hydroxyl radicals by comparison with dimethyl sulfoxide (DMSO) for *OH. All compounds were found to interact with DPPH, most of them to be superoxide anion scavengers and to be strong hydroxyl radical scavengers. Derivatives 1a and 1d substituted on the nitrogen of the indolic nucleus were found to have better antioxidant properties than the reference compounds used and melatonin.