Effect of enzymatically modified isoquercitrin, a flavonoid, on symptoms of Japanese cedar pollinosis: a randomized double-blind placebo-controlled trial.

BACKGROUND

Flavonoids exert antiallergic and antioxidant effects. We investigated the efficacy of enzymatically modified isoquercitrin (EMIQ), a flavonoid, to relieve symptoms of pollinosis.

METHODS

In a parallel-group, double-blind placebo-controlled study design, 20 subjects with Japanese cedar pollinosis took two capsules daily of 100 mg EMIQ or a placebo for 8 weeks during the pollen season. Subjective symptoms and activities of daily living (ADL) scores were recorded every day, and the quality of life (QOL) score was obtained every 4 weeks. Blood sampling was performed before and after the study to measure serum cytokines, chemokines, IgE, quercetin and oxidized biomarkers.

RESULTS

During the entire study period, total ocular score and ocular itching score for the EMIQ group were significantly lower (p < 0.05) than for the placebo group. When limited to the individual periods, total symptom score for the EMIQ group was significantly lower (p < 0.05, week 4-5) than that for the placebo group while other scores for the EMIQ group, such as total nasal score (p = 0.06, week 4-5), nasal obstruction score (p = 0.08, week 4-5), lacrimation score (p = 0.06, week 5-6), ocular congestion score (p = 0.08, week 4-7) and ADL score (p = 0.08, week 4-7), all tended to be lower. The levels of serum cytokines such as interleukin (IL)-4, IL-5, IL-12, IL-13, interferon-gamma, and eotaxin and IgE were not significantly downregulated by the intake of EMIQ but the serum concentrations of oxidized low-density lipoprotein and thymus and activation-regulated chemokine were reduced.

CONCLUSION

Intake of the quercetin glycoside EMIQ was safe and influenced ocular symptoms caused by pollinosis.