Efficacy of Liriope platyphylla extract on improving respiratory function: A CONSORT-randomized, double-blind, placebo-controlled pilot trial

The respiratory system is the first line of defense against outside pollutants. Recently, respiratory health has been receiving increasing attention due to the increase in fine dust, which reduces respiratory function and increases incidence of chronic obstructive pulmonary disease, and in coronavirus pandemic, which can cause severe acute respiratory syndrome. METHODS: This clinical pilot trial was designed to secure evidence for a main clinical trial and to confirm the efficacy and safety of Liriope platyphylla (LP) extract for improving respiratory function. We conducted a double-blind randomized placebo-controlled trial with 22 participants from June 30, 2021, to August 25, 2021. The primary outcome was Breathlessness, Cough, and Sputum Scale score. Secondary outcomes included forced vital capacity, forced expiratory volume at 1 second (FEV1), forced expiratory volume at 1 s/forced vital capacity ratio, cough assessment test score, chronic obstructive pulmonary disease assessment test score, peripheral blood mononuclear cell counts (white blood cells, eosinophils, T cells, and B cells), high-sensitivity C-reactive protein level, erythrocyte sedimentation rate, cytokine (interleukin-1β, interleukin-4, tumor necrosis factor-α, interleukin-6, interleukin-8, interferon-γ, and immunoglobulin E) levels, antioxidant (glutathione peroxidase and superoxide dismutase) levels, and nitric oxide level. RESULTS: A total of 22 participants were randomly assigned to 2 groups: the LP group (n = 11), who took 1000 mg of LP extract per day, and the placebo group, who took 1000 mg of dextrin per day. Participants took 1 capsule twice a day for 4 weeks. For the Breathlessness, Cough, and Sputum Scale, the interaction between group and visit was statistically significant in a blend of analyses of variance. interleukin-8, tumor necrosis factor-α, and interferon-γ levels decreased more in the LP group than in the placebo group. The sample size required for large-scale clinical trials in the future was 50. There were no side effects. CONCLUSION: LP extract can enhance respiratory function. The detailed data we obtained support conducting the future main large-scale clinical trial.