Crystal Structures and Cytotoxicity ofent-Kaurane-TypeDiterpenoids from TwoAspiliaSpecies

Abstract

A phytochemical investigation of the roots ofAspilia plurisetaled to the isolationofent-kaurane-type diterpenoids and additional phytochemicals (1–23).The structures ofthe isolated compounds were elucidated based on Nuclear Magnetic Resonance (NMR)spectroscopic and mass spectrometric analyses. The absolute configurations of seven of theent-kaurane-type diterpenoids (3–6,6b, 7and8) were determined by single crystal X-raydiffraction studies.Eleven of the compounds were also isolated from the roots and theaerial parts ofAspilia mossambicensis. The literature NMR assignments for compounds1and5were revised.In a cytotoxicity assay, 12α-methoxy-ent-kaur-9(11),16-dien-19-oic acid (1)(IC50= 27.3±1.9μM) and 9β-hydroxy-15α-angeloyloxy-ent-kaur-16-en-19-oic acid (3) (IC50=24.7±2.8μM) were the most cytotoxic against the hepatocellular carcinoma (Hep-G2) cell line,while 15α-angeloyloxy-16β,17-epoxy-ent-kauran-19-oic acid (5) (IC50= 30.7±1.7μM) was the mostcytotoxic against adenocarcinomic human alveolar basal epithelial (A549) cells.