Phomopsin A is a mycotoxin produced by the fungus Diaporthe toxica (syn. Phomopsis leptostromiformis). It is a potent and specific inhibitor of eukaryotic protein synthesis, acting by competitively binding to elongation factor 1-alpha (EF-1α), which prevents the binding of aminoacyl-tRNA to the ribosome and halts polypeptide chain elongation. This makes it a valuable tool in biomedical research for studying protein synthesis mechanisms, cell proliferation, cell cycle regulation, and cytoskeleton dynamics indirectly through disrupted protein production. It is utilized in cancer biology to explore antiproliferative effects on rapidly dividing cells and in toxicology as a reference for natural toxins, particularly for its hepatotoxic effects in livestock.