Plant-derived terpenoids in asthma: phytochemical and pharmacological perspectives from a systematic review

Background Asthma is a chronic respiratory disorder characterized by airway inflammation, airway hyperresponsiveness (AHR), and remodeling. Structurally diverse terpenoids offer promising natural compounds with anti-inflammatory, antioxidant, and immunomodulatory properties. Objective To address this gap, this systematic review evaluated the therapeutic potential, mechanisms of action, and translational relevance of terpenoids in experimental asthma models. Search methods Accordingly, following Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines, PubMed, Scopus, and Web of Science (2013–2025) were searched for peer-reviewed in vivo studies evaluating pure herbal terpenoids in asthma. Two independent reviewers conducted study selection and data extraction. Data collection and analysis From the retrieved studies, data on terpenoids, animal models, and key asthmatic biomarkers (AHR, IgE, cytokines, immune cell infiltration, oxidative stress) were systematically extracted by phytochemical subclasses. Bias risk and methodological quality were evaluated using a modified Systematic Review Centre for Laboratory Animal Experimentation (SYRCLE)’s Risk of Bias tool. Main results On this basis, a total of 127 studies were included, predominantly using murine ovalbumin models. Terpenoids alleviated airway inflammation, hyperresponsiveness, and remodeling by regulating Th2 cytokines, IgE, and eosinophilic infiltration. Paeoniflorin, catalpol, farnesol, curcumol, cryptotanshinone, astragaloside IV, withaferin A, and crocin showed marked anti-inflammatory, antioxidant, and anti-remodeling effects by suppressing Th2 cytokines and modulating the NF-κB, Nrf2/HO-1, and TGF-β/Smad pathways, leading to improved airway function and restored redox homeostasis. Conclusions Overall, terpenoids demonstrate preclinical therapeutic promise in mitigating airway hyperresponsiveness and inflammation via regulating Th2/Th1 balance, oxidative stress, and fibrotic signaling. Importantly, all of the evidence synthesized here derives exclusively from preclinical animal models; no clinical trials or human pharmacological data were available, and these terpenoids therefore remain experimental candidates whose clinical relevance is not yet established. However, translational potential is constrained by methodological limitations, particularly insufficient randomization, blinding, and sample size reporting, highlighting the need for more rigorous and standardized studies.