Anti-inflammatory activity of quercetin and isoquercitrin in experimental murine allergic asthma.

Eosinophils and cytokines are implicated in the pathogenesis of allergic diseases. In the present study, we investigate the anti-inflammatory effect of quercetin and isoquercitrin in a murine model of asthma. BALB/c mice were immunized (ovalbumin/aluminum hydroxide, s. c.), followed by two intranasal ovalbumin challenges. From day 18 to day 22 after the first immunization, the mice received daily gavages of isoquercitrin (15 mg/kg) or quercetin (10 mg/kg). Dexamethasone (1 mg/kg, s. c.) was administered as a positive control. Leucocytes were analyzed in bronchoalveolar lavage fluid (BALF), blood and pulmonary parenchyma at 24 h after the last ovalbumin challenge. Interleukin-5 (IL-5) was analyzed in BALF and lung homogenates. In animals receiving isoquercitrin or quercetin, eosinophil counts were lower in the BALF, blood and lung parenchyma. Neutrophil counts in blood and IL-5 levels in lung homogenate were lower only in isoquercitrin-treated mice. No alterations in mononuclear cell numbers were observed. Quercetin and isoquercitrin are effective eosinophilic inflammation suppressors, suggesting a potential for treating allergies.