Preventive effects of quercetin against pulmonary injury Induced by paraquat in rats

Abstract

We examined the antioxidant and anti‐inflammatory components isolated from Moutan radicus cortex. The antioxidant activity toward peroxyl radical, hydroxyl radical, and peroxynitrite was quantified using the Total Oxyradical Scavenging Capacity (TOSC) assay. Among the components examined, the highest TOSC toward peroxyl radical was shown by (+)‐catechin (CT) followed by quercetin (QC), methyl gallate (MG), and gallic acid (GA). The TOSC toward hydroxyl radical was MG > QC > CT > GA. The TOSC toward peroxynitrite was GA > CT > MG > QC. All of the four components decreased the NO release in lipopolysaccharide‐stimulated RAW264.7 cells, but only QC and GA depressed iNOS expression. The protective effects of QC against paraquat (PQ)‐induced pulmonary injury were measured. Rats received an intratracheal dose of PQ and were treated with QC for 2 weeks. The TOSC and GSH levels in lung were reduced and malondialdehyde in lung and NO concentrations in plasma were increased by the PQ challenge, but these changes were inhibited by QC treatment. The elevation of 4‐hydroxyproline in lung tissues was also decreased in the rats treated with QC. Histopathological examination of lung tissues showed similar results. The results suggest that the protective effects of QC against PQ‐induced lung injury are probably associated with its antioxidant activity.