Solanine

Solanine is a glycoalkaloid poison found in species of the nightshade family. It can occur naturally in the any part of the plant, including the leaves, fruit, and tubers. It is very toxic even in small quantities. Solanine has both fungicidal and pesticidal properties, and it is one of the plant's natural defenses.

Solanine Poisoning

Symptoms

Solanine poisoning is primarily displayed by gastrointestinal and neurological disorders. Symptoms include nausea, diarrhea, vomiting, stomach cramps, burning of the throat, headaches and dizziness. Hallucinations, loss of sensation, and paralysis, fever, jaundice, dilated pupils and hypothermia have been reported in more severe cases.

In large quantities, solanine poisoning can cause death. One study suggests that doses of 2 to 5 mg per kilogram of body weight can cause toxic symptoms, and doses of 3 to 6 mg per kilogram of body weight can be fatal.

Symptoms usually occur 8 to 12 hours after ingestion, but may occur as rapidly as 30 minutes after eating high-solanine foods.

Correlation with Birth Defects

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 congenital spina bifida in humans. However other studies have shown no correlation between potato consumption and the incidence of birth defects. ^*

Solanine in Potatoes

Solanine occurs naturally in all nightshades, including tomatoes, Capsicum, and Eggplant, as well as plants from other species. However the most ingested solanine is from the consumption of potatoes.

Potatoes naturally produce solanine and chaconine, a related glycoalkaloid, as a defense mechanism against insects, disease, and predators. Potato leaves and stems are naturally high in glycoalkaloids.

When potato tubers are exposed to light, they turn green and increase glycoalkaloid production. This is a natural defense to help prevent the uncovered tuber from being eaten. The green colour is from chlorophyll, and is itself harmless. However, it is an indication that increased level of solanine and chaconine may be present.

Some diseases, such as potato blight, can dramatically increase the levels of glycoalkaloids present in potatoes. This is believed to be a natural reaction of the plant in response to disease and damage.

Commercial varieties of potatoes are screened for solanine levels, and most have a solanine content of less than 0.2mg/g. However potatoes that have been exposed to light and started to green can show concentrations of 1mg/g or more. In these situations a single unpeeled potato can result in a dangerous dose.

Avoidance

Solanine and chaconine are present in potato shoots. In potato tubers 30–80% of the solanine develops in and under the skin and thus may be removed by peeling and removing the eyes. This is advisable if the tubers show green, but is not a guarantee of safety. Potato greening strongly suggests solanine build-up although each process can occur without the other. A bitter taste in a potato may be a more reliable indicator of toxicity.

Deep-frying potatoes at 170° C (306° F) will effectively lower glycoalkaloid levels, but microwaving is only somewhat effective and boiling is not.

Other uses of Solanine

Solanine has fungicidal and pesticidal properties, and solanine hydrochloride (a modified version of solanine) has been used as a commercial pesticide, but never on a large scale.

Solanine has sedative and anticonvulsant properties, and has been used as a treatment for bronchial asthma, as well as for cough and cold medicines. However, its effectiveness for either use is questionable.

References

External links

Alkaloids

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