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Achyrocline satureioides (Lam.) DC. (Compositae) is a medicinal herb used in Argentina, Uruguay, Brazil and Paraguay for its choleretic, antispasmodic and hepatoprotective properties. The presence of the flavonoid quercetin and its derivatives, and of different phenolic acids such as caffeic, chlorogenic and isochlorogenic acids in the aerial parts of this plant has led us to study the antioxidant activity of its extracts using different bioassays. The inhibition of luminol-enhanced chemiluminescence by the aqueous and methanolic extracts was used to show that their total reactive antioxidant potential index (TRAP; in µM Trolox equivalents) was 91.0 ± 15.4 and 128.1 ± 20.1 µM, respectively, while the total antioxidant reactivity index (TAR) was calculated to be 1537 ± 148 and 1910 ± 171 µM. Only the methanolic extract was capable of reducing iron (II)-dependent DNA damage. Lipid peroxidation was assessed by two different methods. The aqueous extract reduced hydroperoxide-initiated chemiluminescence in rat liver homogenates at all concentrations in a dose-dependent manner, with a calculated IC 50 = 225 µg/ml, while the methanolic extract was only effective at higher concentrations (100 and 1000 µg/ml). Both aqueous and methanolic extracts were capable of reducing the production of thiobarbituric acid reactive substances (TBARS) in rat liver homogenates, with an IC 50 >1000 µg/ml. The results obtained suggest that the extracts of A. satureioides possess significant free radical scavenging and antioxidant activity in vitro, a fact that should encourage future in vivo studies.

The total reactive antioxidant potential (TRAP) and total antioxidant reactivity (TAR) of 4-nerolidylcatechol (4-NC) and methanolic extracts of Pothomorphe umbellata and P. peltata were determined by monitoring the intensity of luminol enhanced chemiluminescence by peroxyl radicals derived from thermolysis of 2,2'-azobis(2-amidinopropane). The highest antioxidant potential was measured in the extract of P. umbellata (TRAP = 97.2 microM) while the highest reactivity was observed in the extract of P. peltata (TAR = 5.0 microM), measured as equivalents of Trolox concentration. These results were higher than those obtained for 4-NC (TRAP = 33.6 microM, TAR = 4.9 microM). DNA sugar damage induced by Fe(II) salts was also used to determine the capacity of 4-NC to suppress hydroxyl radical-mediated degradation of DNA. Calculated IC50 values for 4-NC and catechin, used as a standard, were 25 and 17 microM, respectively.