Tropane alkaloids and toxicity of Convolvulus arvensis.
Horses in a few, localised northern Colorado pastures exhibited weight loss and colic. At PM examination, intestinal fibrosis and vascular sclerosis of the small intestine were identified. The pastures where the affected horses grazed were overrun by field bindweed (Convolvulus arvensis). Bindweed from the pasture was found to contain the tropane alkaloids tropine, pseudotropine, and tropinone and the pyrrolidine alkaloids cuscohygrine and hygrine. Laboratory mice readily ate C. arvensis and exhibited a variety of abnormal clinical signs depending on the amount eaten. Similar alkaloids have been found in other Convolvulus species and cuscohygrine and calystegines (poly-hydroxytropanes) have been previously reported from C. arvensis roots. This is the first report of simple tropane alkaloids in C. arvensis, a world-wide problem weed. Pseudotropine, the major alkaloid, is known to affect digestive tract motility and it is suggested that it might represent a causative agent for the observed cases of equine intestinal fibrosis.