Effect of oral treatment with quercetin on inflammatory and oxidative stress markers in patients with chronic obstructive pulmonary disease.

Airway inflammation plays a major role in the development and progression of chronic obstructive pulmonary disease (COPD). Quercetin, which has potent antioxidant and anti-inflammatory properties reduces lung inflammation in mice displaying COPD-like lung disease. Previously we showed that quercetin was safely tolerated up to 2000 mg/day. We conducted a pilot Phase II clinical trial to examine the effects of quercetin on inflammation in COPD patients. Fourteen COPD patients with ≥ 10 pack-year smoking history and CRP > 3.0 mg/L were randomized in 1:2 ratio to either placebo or quercetin 2000 mg/day for 6 months. Blood and bronchoalveolar lavage fluid (BALF) were collected at baseline and 6 months post-treatment. The reduction of inflammatory and oxidative stress biomarkers in BALF and blood were expressed as change from baseline. Safety of quercetin was assessed based on FEV1 and blood tests. Plasma quercetin levels significantly increased after treatment in only quercetin group. The levels of IL-8, IL-1β, and 8-isoprostane in the BAL and serum SP-D were significantly different from baseline in patients treated with quercetin, but not placebo. The patient-reported disease symptoms showed lowering trend in quercetin-treated group. No study drug-related adverse events were observed as assessed by comprehensive metabolic panel and FEV1. Oral treatment with quercetin was safely and well-tolerated by COPD patients. Quercetin treatment reduced some lung and serum inflammatory biomarkers in COPD. Further prospective studies are necessary to confirm the anti-inflammatory and antioxidant effects of quercetin in COPD patients and to determine if quercetin offers any clinical benefit.