Inhibition of Na+,K+-ATPase activity by (-)-ent-Kaur-16-en-19-oic acid and its derivatives.

The diterpene, (-)- ent-kaur-16-en-19-oic acid, from Croton oblongifolius was identified as an Na +,K +-ATPase inhibitor. This compound exhibits an IC 50 of 2.2 x 10( -5 )M against crude enzyme Na +,K +-ATPase from rat brain.