Qianliguang (senecio scandens) safety dilemma: Dose is the key?

Qianliguang (Senecio scandens) is a common Chinese medicinal herb. Qianliguang-containing herbal proprietary products are registered as over-the-counter remedies in China and exported to Western countries. The safety of using Qianliguang and its products has raised general concerns because of a potential risk of the presence of hepatotoxic pyrrolizidine alkaloids (PAs). A systematic toxicological study is thus required to verify this public concern. In the present article, we report, for the first time, that S. scandens contains nine hepatotoxic PAs with a content of 6.95-7.19 μg/g. At a dose equivalent to the daily intake recommended by the Pharmacopoeia of China, the total content of toxic PAs in Qianliguang was determined to be 3.48 μg/kg/day, which is far below the lowest dose to cause hepatotoxicity (15 μg/kg/day) suggested by the International Program on Chemical Safety. No significant hepatotoxic effects were observed in rats fed with the extract at this human-equivalent dose for 14 consecutive days. However, a single overdose of the herbal water extract (6 g/kg), which was about 8-fold higher than the recommended dose, produced typical PA-induced hepatotoxicity in rats. Therefore, appropriate dosage guidelines should be implemented for the herbal industry, for export/import retailers, and for herbal medicine practitioners to ensure the safe and beneficial use of these herbal medicines.