Osthole is a natural coumarin derivative isolated from plants such as Cnidium monnieri. Recent preclinical studies suggest that osthole exhibits anti-inflammatory, antiproliferative, and immunomodulatory properties relevant to the pathogenesis of psoriasis. Notably, several in vitro and animal model studies have demonstrated that osthole can inhibit the proliferation of keratinocytes and suppress the production of pro-inflammatory cytokines such as TNF-α, IL-6, and IL-17, all of which are implicated in the development of psoriatic lesions. For example, a 2021 study in Frontiers in Pharmacology reported that topical osthole reduced epidermal hyperplasia and inflammation in an imiquimod-induced mouse model of psoriasis.

However, despite these promising findings, there are currently no robust clinical trials in humans that confirm the efficacy or safety of osthole for treating psoriasis. The evidence remains limited to preclinical research, and its translation to clinical practice is not yet established. Therefore, while there is a scientific rationale for investigating osthole in psoriasis, the evidence supporting its use in humans is preliminary. More rigorous clinical studies are required before it can be recommended as a treatment option.