Many plants contain mildly toxic alkaloids but in most cases the concentrations are not high enough to cause a problem.1 Reserpine is concentrated in Rauwolfia serpentina (Indian snakeroot) and this plant has been used for several thousand years in treating a number of aliments. One of the main effects of reserpine is to block the action of dopamine. This blockage causes symptom's that resemble Parkinson's disease. They can be relieved by treating the patient with L-dopa [Monday's Molecule #70].
My first exposure to research was a summer job (1966) in the lab of George Setterfield at Carleton University in Ottawa (Canada). The project was to identify crystal-like inclusions in the cells of Rauwolfia serpentina. The hypothesis was that these inclusions were composed of alkaloids, especially reserpine. As I recall, I didn't make much progress. The inclusions weren't always visible and my suspicion was that they could have been an artifact of the fixation process.
I haven't been able to find any mentions of plant alkaloid inclusions in the literature. Does anyone know this field?
1. It's much safer to eat meat.