A cytotoxic meroterpenoid benzoquinone from roots of Cordia globosa

(1aS*, 1bS*, 7aS*, 8aS*)-4,5-Dimethoxy-1a,7a-dimethyl-1,1a,1b,2,7, 7a,8,8a-octahydrocyclopropa[3,4]cyclopenta[1,2-b]naphthalene-3,6-dione (1), a new meroterpenoid benzoquinone, and microphyllaquinone (2), a known naphthoquinone, have been isolated from roots of Cordia globosa. Both structure determinations were performed by conventional spectroscopic methods, including inverse detection NMR techniques, and by comparison with data from the literature for related compounds. Compound 1 displayed considerable cytotoxic activity against several cancer cell lines with IC50 values in the range of 1.2 to 5.0 mug/mL. The cytotoxic activity seemed to be related to DNA synthesis inhibition, as revealed by the reduction of 5-bromo-2'-deoxyuridine incorpotation, and apoptosis induction, as indicated by the acridine orange/ethidium bromide assay and morphological changes after 24 h of incubation on leukemic cells.