Cytotoxic diterpenoids from Pteris ensiformis.

Phytochemistry investigation on Pteris ensiformis led to the isolation of a new ent-kaurane diterpenoid, ent-kaurane-6β,16α-diol-3-one (1), along with five known diterpenoids (2-6) and three known sesquiterpenes (7-9). Their structures were established by means of spectroscopic methods. The ethanol extract and the isolated compounds (1-9) were evaluated for their antitumor activity against three cancer cell lines.