Hortonones A to C, hydroazulenones from the genus Hortonia.

The new hexahydroazulenones hortonones A (1) to C (3) were isolated from the leaves of three representative species of the endemic Sri Lankan genus Hortonia that belongs to the family Monimiaceae. Hortonones A (1) and B (2) have the unprecedented rearranged hortonane sesquiterpenoid carbon skeleton, and hortonone C (3) has the unprecedented rearranged and degraded 13-norhortonane skeleton. Hortonone C (3) exhibited in vitro cytotoxicity against human breast cancer MCF-7 cells at 5 μg/mL.

Bioactivity and chemistry of the genus Hortonia.

The dichloromethane extracts of the leaves, stem bark, bark and the roots of the three species of the primitive endemic genus Hortonia, H. angustifolia, H. floribunda and H.