Animal experiment:

Mice[2]BALB/c mice are immunized (ovalbumin/aluminum hydroxide, s.c.), followed by two intranasal ovalbumin challenges. From day 18 to day 22 after the first immunization, the mice receive daily gavages of Isoquercitrin (15 mg/kg) or quercetin (10 mg/kg). Dexamethasone (1 mg/kg, s. c.) is administered as a positive control. Leucocytes are analyzed in bronchoalveolar lavage fluid (BALF), blood and pulmonary parenchyma at 24 h after the last ovalbumin challenge. Interleukin-5 (IL-5) is analyzed in BALF and lung homogenates[2].

Isoquercitrin (Isoquercitroside) is an effective antioxidant and an eosinophilic inflammation suppressor.

Isoquercitrin occurs widely in plants.10 μM of Isoquercitrin of the seven compounds partially but significantly blunt the negative effect of H2O2 on RGC-5 cells, as the viability of cells in the presence of H2O2 is increased from approximately 63% to 83% and 90% at 10 and 50 μM, respectively. Indeed, 50 μM Isoquercitrin is more effective as a neuroprotectant than the same concentration of EGCG[1].

In animals receiving Isoquercitrin, eosinophil counts are lower in the BALF, blood and lung parenchyma. Neutrophil counts in blood and IL-5 levels in lung homogenate are lower only in Isoquercitrin-treated mice. No alterations in mononuclear cell numbers were observed[2].

References:
[1]. Jung SH, et al. Isoquercitrin is the most effective antioxidant in the plant Thuja orientalis and able to counteract oxidative-induced damage to a transformed cell line (RGC-5 cells). Neurochem Int. 2010 Dec;57(7):713-21.
[2]. Rogerio AP, et al. Anti-inflammatory activity of quercetin and isoquercitrin in experimental murine allergic asthma. Inflamm Res. 2007 Oct;56(10):402-8.