Chebulinic acid shields Villin 1 from covalent attack to mitigate Euphorbia fischeriana enterotoxicity: A basis for safer anti-ascites therapy

Ethnopharmacological relevance: Euphorbia fischeriana (EF), an herb used in ethnomedicine for cancerous ascites, particularly in Inner Mongolian practices, is limited by severe enterotoxicity. Traditionally, co-decoction with Terminalia chebula (TC) mitigates this toxicity, but the underlying mechanism is unknown, hindering its rational clinical development.

Aim of the study: To elucidate the molecular mechanism by which TC detoxifies EF, providing a scientific basis for developing safer EF-based therapies against malignant ascites.

Materials and methods: The study employed intestinal Organoid models, chemical biology, proteomics, and genetic engineering (Villin 1 knockout/mutagenesis). Enterotoxic EF constituents and protective TC compounds were identified, and their interactions with the cellular target Villin 1 were analyzed in vitro and validated in vivo, assessing effects on F-actin networks and intestinal barrier integrity.

Results: The EF diterpenoid Euphorin G was identified as the enterotoxin, covalently modifying Cys624 in the actin-regulatory protein Villin 1, leading to F-actin disassembly and intestinal barrier failure. Chebulinic acid from TC prevented this by non-covalently binding to Villin 1, shielding Cys624 from Euphorin G and allosterically enhancing Villin 1's F-actin binding affinity. This dual protective mechanism occurred without reducing Euphorin G levels.

Conclusions: This study reveals that Chebulinic acid from TC detoxifies EF by protecting and potentiating the host protein Villin 1 against Euphorin G. This molecular insight validates a traditional ethnopharmaceutical practice, enabling the rational development of safer EF-based therapies for refractory cancerous ascites by preserving therapeutic efficacy while mitigating toxicity.