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The antioxidant activities of the extract and its relevant fraction as well as isolated compounds from the dead bark of Araucaria angustifolia are presented. This tree represents the Mixed Ombrophile Forest, which is endangered due to extensive logging. The dead bark of Araucaria is naturally discarded by the tree, and its hydroalcoholic crude extract has exhibited protective qualities against stress induced by H(2)O(2) in cell culture. Using several in vitro models, here we describe the antioxidant potential of the crude extract and its component ethyl acetate fraction and also of some compounds isolated from the ethyl acetate fraction. We provide the first description of the isolation of two natural product afzelechin derivatives. The extract and isolated compounds, particularly epiafzelechin protocatechuate (5), displayed very high antioxidant activity, as did compound 4, quercetin, which is well known for its antioxidant properties. In a DPPH assay, compound 5 exhibited an IC(50) of 0.7 μM; in a lipid peroxidation assay; IC(50) values of 21 μM and 35 μM were obtained when the oxidation was induced by UV and ascorbate free radicals, respectively.

The antioxidant activity of a methanolic extract of Bombax ceiba was evaluated using several antioxidant assays, in terms of its: (i) ability to scavenge DPPH (1,1-diphenyl-2-picryl-hydrazyl) and hydroxyl free radicals; (ii) action against lipid peroxidation (in rat liver microsomes and soy bean phosphatidylcholine liposomes), induced by ascorbyl radicals and peroxynitrite; and (iii) effect on myeloperoxidase activity. The cytotoxicity was monitored through the mitochondrial activity in the Vero cell line. The extract showed antioxidant activity in all assays, the EC(50) (microg/ml) for DPPH was 87 and for lipid peroxidation of microsomes and soy bean liposomes induced by ascorbyl radicals were 141 and 105, respectively, and by peroxynitrite were 115 and 77, respectively. The K(0.5) value for myeloperoxidase activity inhibition by the extract was 264 microg/ml. The extract showed very low toxicity toward Vero cells.

Albendazole (ABZ) and mebendazole (MBZ) are two benzimidazole-derived drugs that show remarkable antihelmintic activity and are widely used in the treatment and control of helminths. Some antihelmintic drugs seem to act through the deleterious generation of reactive oxygen and nitrogen species (ROS and RNS, respectively) to which helminths have no, or relatively low, antioxidant defences (AD), when compared to aerobic organisms. The main objective of the present study consisted of the evaluation of the effect of both drugs on the AD and on some oxidative stress indicators in the host liver. Adult, male, Wistar rats were treated with ABZ or MBZ at doses of 40 mg/kg for different periods of time (2, 4, 8 and 10 days). After treatment, the activities of superoxide dismutase, catalase, glutathione reductase, and glutathione S-transferase, as well as the concentrations of TBARS, reduced glutathione, oxidized glutathione and total glutathione, were evaluated in rat hepatocytes. The serum nitrogen monoxide, usually known as nitric oxide (NO) levels, was also measured. The results showed that both drugs provoked an oxidative stress condition, demonstrated through the elevation of TBARS contents and through the decrease of some AD. Moreover, ABZ showed to be a strong ROS and RNS generator while MBZ showed a low and transient effect on ROS generation. It is suggested that MBZ could be the first-choice drug in the treatment of helminthiasis because it shares a similar therapeutic indication with ABZ, and because it causes only a mild oxidative stress to the host.

Calendula officinalis (marigold) has many pharmacological properties. It is used for the treatment of skin disorders, pain and also as a bactericide, antiseptic and anti-inflammatory. Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are known to participate in the pathogenesis of various human diseases and may be involved in the conditions which C. officinalis is used to treat. The aim of this study was to investigate the relationship between the beneficial properties of this plant and its antioxidant action. The butanolic fraction (BF) was studied because it is non-cytotoxic and is rich in a variety of bioactive metabolites including flavonoids and terpenoids. Superoxide radicals (O(2)(*-)) and hydroxyl radicals (HO(*)) are observed in decreasing concentrations in the presence of increasing concentrations of BF with IC(50) values of 1.0 +/- 0.09 mg/ml and 0.5 +/- 0.02 mg/ml, respectively, suggesting a possible free radical scavenging effect. Lipid peroxidation in liver microsomes induced by Fe(2+)/ascorbate was 100% inhibited by 0.5 mg/ml of BF (IC(50) = 0.15 mg/ml). Its total reactive antioxidant potential (TRAP) (in microM Trolox equivalents) was 368.14 +/- 23.03 and its total antioxidant reactivity (TAR) was calculated to be 249.19 +/- 14.5 microM. The results obtained suggest that the butanolic fraction of C. officinalis possesses a significant free radical scavenging and antioxidant activity and that the proposed therapeutic efficacy of this plant could be due, in part, to these properties.