Minor components of potatoes and tomatoes that are toxic if consumed in large quantities. Steroidal alkaloids are mainly present as glycosides in the family of Solanaceae, including the potato and the tomato. The major glycoalkaloids in potatoes are solanine and chaconine, both glycosides of solanidine. Solanine and chaconine are potent irritants of the intestinal mucosa and cholinesterase inhibitors, the first being the most active. Poisoning with either substance can result in gastrointestinal symptoms of vomiting and diarrhea, and neurological symptoms such as irritability, confusion, delirium, and respiratory failure, which may ultimately result in death. Furthermore, poisoning is often accompanied by high fever. In general, the glycoalkaloid contents of potato tubers do not pose harmful effects in humans. Serious poisonings have been reported following the consumption of large amounts of potatoes with high glycoalkaloid contents (≥200 mg/kg). Potatoes that have been exposed to light and those that are diseased by fungal infection or mechanically bruised may contain toxic levels of glycoalkaloids. The major glycoalkaloid in tomatoes is α-tomatidine, with tomatidenol as the aglycone. It is present in all parts of the plant. In the fruit, the concentration decreases during ripening. Poisonings in humans due to the consumption of tomatoes have not been reported.