New Bioactive Clerodane Diterpenoids from the Roots of Casearia membranacea

Bioassay-guided fractionation of acetone extracts of the roots of Casearia membranacea furnished three new clerodane diterpenes, caseamembrins S  U (13) and the known caseamembrin Q (4). The structures of 13 were established by extensive spectroscopic analyses, especially 2D NMR. Compounds 1-4 were tested against human tumor cells including HeLa (cervical epitheloid carcinoma), DLD-1 (colon carcinoma), Daoy (medulloblastoma), and KB (oral epidermoid carcinoma) cell lines. Among them, caseamembrin T exhibited the most potent activity against medulloblastoma tumor cells, superior to minomycin.