Trisnor-Euphane-Type Triterpenoid and Other Constituents Isolated from Euphorbia tanquahuete Sessé & Moc.: Preparation and Cytotoxic Evaluation of Semisynthetic Derivatives of Euphol

[Image: see text] The natural compound 25,26,27-trisnor-3β-hydroxy-euphan-24-al (1) was isolated for the first time from the bioactive extract of the leaves of Euphorbia tanquahuete, together with the known compounds euphol, eupha-8,23-dien-3β,25-diol, lupeol, cycloeucalenol, β-sitosterol, squalene, and 1-octacosanol. The structure of the new compound was elucidated based on extensive analysis of spectroscopic data and by semisynthesis from euphol. The chemical modification of the alcohol at C3 and the side chain of euphol afforded seven derivatives (6–12). The cytotoxic activity of the natural and semisynthetic compounds evaluated against a panel of human cancer cell lines showed selectivity for certain cell lines and indicated that natural compound 1 and semisynthetic 8 were the most active against leukemia (K562) cell line.