Bisabolane-Type Sesquiterpenoids from the Whole Plant of Parasenecio rubescens

Twenty-two new highly oxygenated
bisabolane-type sesquiterpenoids, pararubin A–V (1–22), were isolated from the whole plant of Parasenecio rubescens. The structure determination
of 1–22, including the assignment
of their relative configurations, was accomplished by extensive 1D
and 2D NMR spectroscopy. The absolute configuration of pararubin A
(1) was established by single-crystal X-ray crystallographic
analysis. The isolated compounds were evaluated for their cytotoxic
effects against three cancer cell lines (B16 mouse melanoma cells,
HepG2 human hepatocellular carcinoma cells, and MCF7 human breast
adenocarcinoma cells) and for their antimicrobial effects against Staphylococcus aureus, Escherichia
coli, and Monilia albicans.