Osthole is a natural coumarin derivative predominantly found in plants such as Cnidium monnieri. There is emerging scientific interest in its potential anti-inflammatory and immunomodulatory properties, which are relevant to rheumatoid arthritis (RA). Preclinical studies, primarily performed in vitro and in animal models, indicate that osthole can inhibit the production of pro-inflammatory cytokines (including TNF-α, IL-6, and IL-1β), suppress NF-κB signaling, and reduce oxidative stress—all of which play roles in the pathogenesis of RA. For example, research published in International Immunopharmacology (2020) demonstrated that osthole ameliorated joint inflammation and damage in collagen-induced arthritis mice via modulation of immune responses and inflammatory mediators.

However, there are currently no high-quality clinical trials in humans specifically investigating osthole for RA. The available evidence is confined to laboratory and animal studies, which show promise but have not yet translated into confirmed efficacy or safety in humans. Osthole is not a conventional or widely recognized therapy for RA in either traditional medicine or mainstream clinical practice. In summary, while there is scientific interest and some preliminary evidence, its use for RA is not yet strongly supported, and further human studies are needed.