Highly oxidized sesquiterpenoids from Parasenecio rubescens and assessment of their cytotoxicity

A phytochemical investigation of the whole plant of Parasenecio rubescens (S. Moore) Y. L. Chen yielded 14 previously undescribed, highly oxidized bisabolane-type sesquiterpenoids, named pararunines L–Y, along with one known oplopane-type sesquiterpenoid. The structural elucidation of these compounds was accomplished through comprehensive spectroscopic analysis, including nuclear magnetic resonance (NMR) and high-resolution electrospray ionization mass spectrometry (HR-ESI-MS) techniques. Motivated by traditional uses and previous studies on this genus, all isolated compounds were subjected to in vitro cytotoxicity assays against four human cancer cell lines (MCF-7, Hela, HCT116, and HT-29). Considering that the reported chemical constituents of numerous other species within this genus primarily consist of eremophilane-type sesquiterpenoids, our findings not only expand the structural diversity of bisabolane-type sesquiterpenoids but also contribute valuable scientific evidence to the chemotaxonomy of this genus.