Clerodane diterpenoids from Casearia kurzii and their cytotoxic activities.

A search for bioactive natural products as anticancer lead compounds resulted in the isolation of one previously undescribed and three known clerodane diterpenoids (1-4) from Casearia kurzii. The structures of these compounds were established by analysis of their NMR, MS, and electronic circular dichroism data. The cytotoxic activities of four compounds against three human cancer cell lines were evaluated. Compound 2 was found to be the most active with an IC₅₀ value of 4.1 μM against HeLa cells, and was selected to investigate the possible cytotoxic mechanism.