INHIBITION OF LIPID-PEROXIDATION AND IRON(II)-DEPENDENT DNA-DAMAGE BYEXTRACTS OF POTHOMORPHE-PELTATA (L) MIQ

Leaves of Pothomorphe peltata (L.) Mig. (Piperaceae) are used locally as anti-inflammatory, antipyretic, hepatoprotective and diuretic infus ions and to treat external ulcers and local infections in several part s of the Peruvian, Bolivian and Brazilian Amazon region. The antioxida nt activity of different extracts of P. peltata was studied using the hydroperoxide-initiated chemiluminescence assay in liver homogenates, and the methanolic extract was found to have the highest antioxidant a ctivity, with an IC50 = 4 mu g/ml. Aqueous and dichloromethane extract s did not show antioxidant activity. The extracts were further evaluat ed using the thiobarbituric acid-reactive substances (TEARS) assay. Fi nally, an assay of DNA sugar damage induced by Fe (II) salt was used t o determine the capacity of the extracts to suppress the oxidative deg radation of DNA. All the extracts showed antioxidant activity in the l atter two bioassays. The methanolic extract showed the highest activit y in reducing oxidative damage to DNA, with an IC50 = 5 mu g/ml. Since this extract was highly effective in reducing chemiluminescence and D NA damage, and because the latter activity could be due to the presenc e of compounds that bind to DNA, DNA-binding activity was studied usin g the DNA-methyl green (DNA-MG) bioassay. A 30% decrease in the initia l absorbance of DNA-MG complex was observed in the methanolic extract at 1000 mu g/ml, suggesting the presence of compounds that bind to gen etic material. No DNA-binding activity was observed in the aqueous or dichloromethane extracts.