Chinese herbal medicine for ulcerative colitis: product-level clinical evidence, mechanistic appraisal, and a roadmap to precision translation

Chinese herbal medicine (CHM) is widely used for ulcerative colitis (UC), but product heterogeneity, variable trial quality, and limited long-term safety data preclude class-level efficacy claims. This critical narrative review therefore evaluates evidence at the level of the defined botanical drug product, formulation, route, dose, and manufacturing process. The review focuses on traditional formulas, processed botanical drugs, and proprietary preparations with documented use in Chinese medical practice. Purified plant metabolites such as curcumin and common flavonoids are not treated as uniquely Chinese interventions; they are discussed only when they are part of a defined CHM-related product or when pivotal natural-product trials provide a relevant product-level comparator. Primary randomized trials show heterogeneous results: higher-dose curcumin trials and the curcumin-QingDai combination provide signals of benefit, low-dose curcumin was negative, and indigo naturalis shows dose-related efficacy accompanied by important safety concerns. Mechanistically, the strongest evidence comes from human target engagement or causal perturbation, exemplified by mucosal CYP1A1 induction with curcumin-QingDai and loss of indigo naturalis efficacy in Ahr-deficient mice. Most other mechanistic claims remain preclinical and model-dependent. Translation requires taxonomically authenticated and chemically characterized products, measured exposure, causal mechanism testing, objective CORE-IBD/STRIDE-II-aligned outcomes, CONSORT-CHM reporting, and prospective, batch-traceable pharmacovigilance. No molecular, microbial, or traditional-pattern biomarker has yet shown a prospectively validated treatment-by-biomarker interaction for a defined CHM product. Precision translation should therefore be regarded as a prospective research program rather than an achieved clinical state.