Plant-Derived Bioactive Compounds in Chronic Obstructive Pulmonary Disease: Targeting Oxidative Stress and Inflammatory Signaling

Chronic obstructive pulmonary disease (COPD) is characterised by persistent airflow limitation arising from chronic inflammation, oxidative stress, mucus hypersecretion, protease–antiprotease imbalance, airway remodelling, and emphysematous destruction. This review evaluates plant-derived bioactive compounds with reported activity against molecular processes implicated in COPD. Resveratrol, kaempferol, quercetin, fisetin, epigallocatechin gallate, gallic acid, ursolic acid, hesperidin, apigenin, and luteolin are examined with emphasis on Nrf2, NF-κB, MAPKs, PI3K/Akt, SIRT1, TLR4, and NLRP3 signalling. In selected cellular and animal models, these compounds have been reported to reduce oxidative stress, inflammatory mediator release, mucus production, metalloproteinase activity, and tissue injury. However, these experimental findings do not establish therapeutic efficacy in patients with COPD. Some also affect autophagy, corticosteroid sensitivity, and pathways associated with cellular senescence. Overall, the evidence is derived mainly from cultured cells and animal models, with limited clinical data. Poor oral bioavailability, rapid metabolism, uncertain pulmonary exposure, formulation variability, dose standardisation, and potential drug interactions remain major translational limitations. Future studies should define pharmacokinetics, lung tissue exposure, optimal formulations, safety, and interactions with standard COPD therapies, followed by adequately powered clinical trials assessing exacerbations, lung function, symptoms, exercise capacity, quality of life, and treatment-related adverse effects in well-defined COPD populations.