Ent-abietane and ent-pimarane diterpenoids from Croton mubango (Euphorbiaceae)

Twelve ent-abietane and two ent-pimarane diterpenoids were isolated from the leaves of Croton mubango Mull. Arg. (Euphorbiaceae) collected in the Democratic Republic of the Congo. 2 beta-Hydroxy-ent-abieta-7,13-dien-3-one, 15-hydroxy-ent-abieta-7,13-dien-3-one, 13 alpha,15-dihydroxy-ent-abieta-8(14)-en-3-one, 2 beta,9,13-trihydroxy-ent-abieta-7-en-3-one, 2 beta,7 beta-dihydroxy-ent-abieta-8,11,13-trien-3-one, 15-hydroxy-ent-abieta-8,11,13-trien-3-one and ent-pimara-8(14),15-dien-3-one and the ent-forms of the previously reported normal series diterpenoids, ent-abieta-8,11,13-trien-3-one, 7 beta-hydroxy-ent-abieta-8,11,13-trien-3-one, 3 alpha-hydroxy-ent-abieta-8,11,13-triene, 15-hydroxy-ent-abieta-8,11,13-triene and 6 beta-hydroxy-ent-abieta-8,11,13-triene are reported here for the first time. Structures were established using HRESIMS, FTIR, NMR, DP4 + probability calculations and by comparison of the experimental and calculated electronic circular dichroism (ECD) spectra. Ent-pimara-8(14), 15-dien-3-one, showed antiproliferative activity against melanoma (MALME-3M), renal (UO-31) and ovarian cancer cell lines (IGROV1) at a concentration of 10(-5) M in the NCI 60 screen.