Phorbol 98% (CAS:17673-25-5) is a high-purity diterpenoid isolated from Croton tiglium seeds, serving as the foundational compound for tumor-promoting phorbol esters like PMA. With ≥98% HPLC-verified purity and characteristic needle crystals, it enables critical research in PKC-mediated carcinogenesis, apoptosis resistance, and multi-drug resistance reversal.