Solanine is a glycoalkaloid poison found in species of the nightshade family within the genus Solanum, such as the potato (Solanum tuberosum). It can occur naturally in any part of the plant, including the leaves, fruit, and tubers. Solanine has pesticidal properties, and it is one of the plant's natural defenses. Solanine was first isolated in 1820 from the berries of the European black nightshade (Solanum nigrum), after which it was named. It belongs to the chemical family of saponins.

Solanine poisoning is primarily displayed by gastrointestinal and neurological disorders. Symptoms include nausea, diarrhea, vomiting, stomach cramps, burning of the throat, cardiac dysrhythmia, nightmares, headache, dizziness, itching, eczema, thyroid problems, and inflammation and pain in the joints. In more severe cases, hallucinations, loss of sensation, paralysis, fever, jaundice, dilated pupils, hypothermia, and death have been reported.

Ingestion of solanine in moderate amounts can cause death. One study suggests that doses of 2 to 5 mg/kg of body weight can cause toxic symptoms, and doses of 3 to 6 mg/kg of body weight can be fatal.

Symptoms usually occur 8 to 12 hours after ingestion, but may occur as rapidly as 10 minutes after eating high-solanine foods.^{[citation needed]}

Some studies show a correlation between the consumption of potatoes suffering from late blight (which increases solanine and other glycoalkaloid levels) and the incidence of spina bifida in humans.^{[citation needed]} However, other studies have shown no correlation between potato consumption and the incidence of birth defects.

Livestock can also be susceptible to glycoalkaloids. High concentrations of solanine are necessary to cause death to mammals. The gastrointestinal tract cannot efficiently absorb solanine, which helps decrease its strength to the mammal body. Livestock can hydrolyze solanine and excrete its contents to diminish its presence in the body.

There are several proposed mechanisms of how solanine causes toxicity in humans, but the true mechanism of action is not well understood. Solanum glycoalkaloids have been shown to inhibit cholinesterase, disrupt cell membranes, and cause birth defects. One study suggests that the toxic mechanism of solanine is caused by the chemical's interaction with mitochondrial membranes. Experiments show that solanine exposure opens the potassium channels of mitochondria, increasing their membrane potential. This, in turn, leads to Ca²⁺ being transported from the mitochondria into the cytoplasm, and this increased concentration of Ca²⁺ in the cytoplasm triggers cell damage and apoptosis. Potato, tomato, and eggplant glycoalkaloids like solanine have also been shown to affect active transport of sodium across cell membranes. This cell membrane disruption is likely the cause of many of the symptoms of solanine toxicity, including burning sensations in the mouth, nausea, vomiting, abdominal cramps, diarrhea, internal hemorrhaging, and stomach lesions.

Solanine is a glycoalkaloid poison created by various plants in the genus Solanum, such as the potato plant. When the plant's stem, tubers, or leaves are exposed to sunlight, it stimulates the biosynthesis of solanine and other glycoalkaloids as a defense mechanism so it is not eaten. It is therefore considered to be a natural pesticide.^{[citation needed]}