Gelsemium poisoning mediated by the non-toxic plant Cassytha filiformis parasitizing Gelsemium elegans.

Introduction: Gelsemium poisoning is caused by consumption of the deadly Gelsemium species such as Gelsemium elegans, leading to significant gastrointestinal, neurological and cardio-respiratory toxicities. In 2011 (Cluster 1) and 2012 (Cluster 2), the authors encountered two clusters of gelsemium poisoning after consumption of the non-toxic parasitic plant Cassytha filiformis. The current study aims to examine the mechanism of gelsemium poisoning mediated by a benign parasitic plant.

Methods: Qualitative analysis of toxic gelsemium alkaloids using liquid chromatography-tandem mass spectrometry (LC-MS/MS) was performed on the herbal and urine samples from both clusters to confirm exposure. Morphological examination, qualitative analysis of aporphine alkaloids using liquid chromatography-ion trap-time of flight mass spectrometry (LC-IT-TOF/MS) and Sanger sequencing were performed on the plant sample from Cluster 2 to confirm its identity. A field study was conducted in local countryside and C. filiformis was collected for histological, LC-MS/MS and LC-IT-TOF/MS analyses to study its interaction with G. elegans.

Results: Gelsemium alkaloids that are not naturally present in C. filiformis were detected in the patients' herbal and urine samples. Misidentification and contamination with G. elegans during the preparation process were excluded by morphological examination of the plant sample from Cluster 2. Its identity as C. filiformis was verified with LC-IT-TOF/MS and molecular analyses. Histological, LC-MS/MS and LC-IT-TOF/MS analyses of C. filiformis collected during the field study confirmed that its haustoria penetrated the vascular bundles of G. elegans and absorbed its gelsemium toxins.

Conclusions: The non-toxic plant C. filiformis absorbed toxic gelsemium alkaloids from its host, G. elegans, and led to gelsemium poisoning in our patients. Our study provides new insights into the toxicology of such plants. Benign parasitic plants may lead to potentially life-threatening poisoning if it parasitizes toxic hosts and absorbs their phytotoxins. The public awareness of risks associated with the use of these medicinal parasitic plants should be raised.