| Summary: | A phytochemical investigation of the roots of <i>Aspilia pluriseta</i> led to the isolation of <i>ent</i>-kaurane-type diterpenoids and additional phytochemicals (<b>1</b>⁻<b>23</b>). The structures of the isolated compounds were elucidated based on Nuclear Magnetic Resonance (NMR) spectroscopic and mass spectrometric analyses. The absolute configurations of seven of the <i>ent</i>-kaurane-type diterpenoids (<b>3</b>⁻<b>6</b>, <b>6b, 7</b> and <b>8</b>) were determined by single crystal X-ray diffraction studies. Eleven of the compounds were also isolated from the roots and the aerial parts of <i>Aspilia mossambicensis</i>. The literature NMR assignments for compounds <b>1</b> and <b>5</b> were revised. In a cytotoxicity assay, 12α-methoxy-<i>ent</i>-kaur-9(11),16-dien-19-oic acid (<b>1</b>) (IC<sub>50</sub> = 27.3 ± 1.9 µM) and 9β-hydroxy-15α-angeloyloxy-<i>ent</i>-kaur-16-en-19-oic acid (<b>3</b>) (IC<sub>50</sub> = 24.7 ± 2.8 µM) were the most cytotoxic against the hepatocellular carcinoma (Hep-G2) cell line, while 15α-angeloyloxy-16β,17-epoxy-<i>ent</i>-kauran-19-oic acid (<b>5</b>) (IC<sub>50</sub> = 30.7 ± 1.7 µM) was the most cytotoxic against adenocarcinomic human alveolar basal epithelial (A549) cells.
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