Euphosantianane A⁻D: Antiproliferative Premyrsinane Diterpenoids from the Endemic Egyptian Plant Euphorbia Sanctae-Catharinae

species are rich in diterpenes. A solvent extraction of , a species indigenous to the Southern Sinai of Egypt, afforded several premyrsinane diterpenoids ( ⁻ ) as well as previously reported metabolites ( ⁻ ) that included three flavonoids. Isolated compounds were chemically characterized by spectroscopic analysis. Identified compounds were bioassayed for anti-proliferative activity in vitro against colon (Caco-2) and lung (A549) tumor cell lines. Compound exhibited robust anti-proliferative activity against A549 cells (IC = 3.3 µM). Absolute configurations for versus were determined by experimental and TDDFT-calculated electronic circular dichorism (ECD) spectra.