Sesquiterpenoids and monoterpenoid coumarins from Parasenecio rubescens

Ten new sesquiterpenoids (1–2, 5–9, 12–14) and four new monoterpenoid coumarins (15–18), along with four known sesquiterpenoids (3, 4, 10, 11) and one known monoterpenoid coumarin (19), were isolated from the whole plant of Parasenecio rubescens. The structures of the isolates were determined through comprehensive spectroscopic analyses and HRESIMS data, with the isolated sesquiterpenoids being classified into oplopane-type (1–4) and bisabolane-type (5–14). The absolute configuration of 1 was established by single-crystal X-ray diffraction analysis with Cu Kα radiation. The cytotoxic effects against three cancer cell lines (B16 mouse melanoma cells, HepG2 human hepatocellular carcinoma cells, and MCF7 human breast adenocarcinoma cells) of the isolated compounds, as well as their antimicrobial effects against Staphylococcus aureus, Escherichia coli, and Monilia albicans, were evaluated. This study demonstrates that the unusual monoterpenoid coumarins, highly oxygenated oplopane-type and bisabolane-type sesquiterpenoids could have an important chemotaxonomic significance for the genus Parasenecio.