Researchers analyzed the levels of pyrrolizidine alkaloids (PAs) in Eupatorium fortunei herbs and products derived from them. They found that the total PA amounts varied widely, with some exceeding the recommended intake limit. The study also showed that some PAs were neurotoxic to neural progenitor cells (NPCs) in vitro. Specifically, intermedine, intermedine N-oxide, and lycopsamine N-oxide decreased cell viability at 30 μM, and intermedine N-oxide inhibited oligodendrogenesis of NPCs at 10 μM. While short-term intake seemed unlikely to lead to acute toxic effects, chronic use warranted caution. These findings highlight the need for safe monitoring of herbs and herbal products containing PAs.