Friedelane Triterpenes with Cytotoxic Activity from the Leaves of Maytenus quadrangulata (Celastraceae)

Three new triterpenes, 3,4-seco-3,110-epoxyfriedel-4(23 )-en-3 beta-01 (1), friedelan-3 alpha,11 beta-diol (2), 7 beta,26-epoxyfriedelan-3a,7a-diol (3), a mixture of two new triterpenes 3 alpha-hydroxyfriedelan-29-y1 palmitate (4) and 3 alpha-hydroxyfriedelan-29-yl stearate (5) and eleven known compounds were obtained from the hexane extract of Maytenus quadrangulata leaves. The structures and the relative stereochemistry of the new triterpenes were established through 1D/2D nuclear magnetic resonance (NMR), high resolution mass spectrometry (HRMS), and Fourier transform infrared (FTIR) spectral data. The hexane extract and isolated compounds were submitted to the cytotoxicity assays against leukemia (THP-1 and K562), ovarian (TOV-21G) and breast cancer (MDA-MB-231) cell lines. Compounds 1, 2 and 11 beta-hydroxyfriedelan-3-one (15) displayed high cytotoxicity and selectivity against leukemic cells when compared to positive control cytarabine (for THP-1) and imatinib (for K562). Furthermore, compound 2 showed similar cytotoxicity and an enhanced selectivity towards ovarian and breast cells in comparison to positive control etoposide.