New humulenes from Hyptis incana (Labiatae).

Two new humulene-type sesquiterpenes, named hyptishumulene I (1) and II (2), have been isolated, together with eight known compounds, a humulene-type sesquiterpene (3), a monoterpene (4) and six abietane-type diterpenoids (5-10) from the aerial parts of Hyptis incana (Labiatae). The cytotoxic activity of the isolated compounds against mouse leukemia cells (L1210) was examined. The abietane-type diterpenoids (5-10) showed rather potent growth inhibitory activity (IC50<15 microM), while the new humulene-type compounds (1 and 2) exhibited moderate activity (IC50>50 microM).