Quassinoids from the Root Barks of Ailanthus altissima: Isolation, Configurational Assignment, and Cytotoxic Activities

Main observation and conclusion Quassinoids, a class of highly oxygenated triterpenes, have been isolated as bitter principles from the plants of Simaroubaceae family. Five new quassinoids, chouchunlactone A—E (1—5), and two known ones were identified from the root barks of Ailanthus altissima Swingle (Simaroubaceae). The chemical structures of the new compounds were deduced by spectroscopic data analyses, NMR calculations and DP4+ probability analysis. The absolute configurations were defined by comparison of their experimental and calculated electronic circular dichroism (ECD) spectra data, and compounds 1—2 were further confirmed by single‐crystal X‐ray diffraction. Biologically, compound 5 showed potencies equivalent to sorafenib (IC50 value, 9.70 μmol·L–1) against HepG2 cells. The Hoechst 33342 staining, JC‐1 fluorescent dye and Annexin V/PI analysis studies demonstrated that 5 can induce apoptosis and attenuate mitochondrial membrane potential (MMP) in HepG2 cells. Five new quassinoids, chouchunlactone A—E (1—5), and two known ones were identified from the root barks of A. altissima Swingle. Biologically, compound 5 showed potencies equivalent to sorafenib against HepG2 cells.