Cytotoxic 8,9-<i>seco</i>-ent-kaurane diterpenoids from <i><i>Croton kongensis</i></i>

<p>Chemical study on the ethanolic extract generated from the aerial parts of <i>Croton kongensis</i> led to the isolation of three new 8,9-<i>seco</i>-ent-kaurane diterpenoids, kongeniods A‒C (<b>1</b>‒<b>3</b>), together with seven known analogs (<b>4</b>–<b>10</b>). The structures of these compounds were assigned by spectroscopic data analysis. The <i>vitro</i> cytotoxic tests showed that compounds <b>1</b>–<b>3</b> exhibited strong activities against HL-60 cell lines with IC₅₀ values of 0.47, 0.58, and 1.27 μM, respectively.