Oxidative stress in earthworms short- and long-term exposed to highly Hg-contaminated soils.

Exposure to mercury is often assessed by the measurement of molecular and biochemical antioxidant defences against an excessive production of reactive oxygen species. Here we examined some selected biomarkers of oxidative stress in the earthworm Lumbricus terrestris short- (2d) and long-term (44 d) exposed to Hg-contaminated soils (up to 1287 mg/kg dry wt). This level of Hg exposure did not cause earthworm mortality, however it yielded organisms to a situation of oxidative stress which was evidenced by the time-dependent responses of biomarkers. The reduced to oxidized glutathione ratio was a sensitive and early biomarker of Hg exposure, although the glutathione reductase activity back returned their normal physiological concentrations. Metallothioneins and total glutathione seemed to have a significant role in reducing Hg-induced oxidative stress when exposure to Hg prolonged up to 44 d. We combined biomarker responses into an integrate biomarker index which positively correlated with the Hg concentrations measured in the postmitochondrial fraction of the earthworm muscle, and with the available Hg fraction in soil. Current results suggest that glutathione redox cycle can be a complementary tool in the exposure and effect assessment of Hg-polluted soils.

Antimicrobial activity against Helicobacter pylori strains and antioxidant properties of blackberry leaves (Rubus ulmifolius) and isolated compounds.

Rubus spp. (Rosaceae) provide extracts used in traditional medicine as antimicrobial, anticonvulsant, muscle relaxant and radical scavenging agents. Resistance to antibiotics used to treat Helicobacter pylori infection as well as their poor availability in developing countries prompted us to test the antimicrobial activity of Rubus ulmifolius leaves and isolated polyphenols against two H. pylori strains with different virulence (CagA+ strain 10K and CagA(-) strain G21). The antioxidant activity (TEAC values) of the tested compounds ranged from 4.88 (gallic acid) to 1.60 (kaempferol), whilst the leaf extract gave a value of 0.12. All the isolated polyphenols as well as the leaf extract showed antibacterial activity against both of the H. pylori strains. The minimum bactericidal concentrations (MBCs) of the extract for H. pylori strains G21 and 10K, respectively, were 1200 microg/mL and 1500 microg/mL after 24h of exposure and 134 microg/mL and 270 microg/mL after 48 h exposure. Ellagic acid showed very low MBC values towards both of the H. pylori strains after 48 h (2 microg/mL and 10 microg/mL for strains G21 and 10K, respectively) and kaempferol toward G21 strain (MBC=6 microg/mL). A relationship between antimicrobial activity and antioxidant capacity was found only for H. pylori strain G21 CagA(-) strain.