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 μM), while the new humulene-type compounds (1 and 2) exhibited moderate activity (IC50>50 μM).
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The diastereomeric isomer at C-7 of 1 has been prepared by acid hydrolysis of humulene diepoxide A (SmithR.J., MahiouB., DeinzerM.L. (1991) Hydrolysis products of humulene diepoxide. Tetrahedron, 47, 933–940). A comparison of the spectral data of 1 with those of the compound from humulene diepoxide A showed that these compounds were not identical.
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The experimental results on the apoptosis inducement were already published in Anticancer Research. (TabataK., KimM., MakinoM., SatohM., SatohY., SuzukiT. (2012) Phenolic diterpenes derived from Hyptis incana induce apoptosis and G2/M arrest of neuroblastoma cells. Anticancer Research, 32, 4781–4790.
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IshiyamaN., MiyazonoY., SasamotoK., OhkuraY., UenoK. (1997) A highly water-soluble disulfonated tetrazolium salt as a chromogenic indicator for NADH as well as cell viability. Talanta, 44, 1299–1305.
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