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Chaconine and Solanine
Dateline: 01/17/00
By Alan Bruzel
What Are Chaconine and Solanine?
These are naturally occurring toxins found in many edible and non-edible members of the Solanaceae family, such as eggplant (Solanum melongena), nightshade (S. americanum and S. nigrum), and potato (S. tuberosum). Chemically, they are steroidal glycoalkaloids in which the steroid alkaloid solanidine, pictured below, is attached to a trisaccharide group. Chaconine and solanine have different trisaccharides bound to the solanidine moiety.
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Solanidine (R = H). In chaconine and solanine, R = trisaccharide component. |
In alpha-chaconine, the trisaccharide contains one molecule of glucose and two molecules of rhamnose:
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alpha-Chaconine |
In alpha-solanine, the trisaccharide consists of one molecule of glucose, one molecule of galactose, and one molecule of rhamnose:
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alpha-Solanine |
Just How Poisonous Are These Compounds?
About as poisonous as strychnine. A fatal oral dose for an adult would be about 420 milligrams. Chaconine and solanine inhibit the activity of acetylcholinesterase, and at high levels can block nerve transmission.
Glycoalkaloid Levels in Potatoes
Most potatoes sold for consumption have about 15 milligrams total of both chaconine and solanine in a 200-gram potato. Potatoes with solanine levels greater than 14 milligrams per 100 grams are bitter in taste.
How Do I Limit My Intake of These Toxins?
First, avoid eating green potatoes. Exposure to light or stress (or even aging) causes transformation of a potato's amyloplasts to chloroplasts, followed by the synthesis of the green pigment, chlorophyll. Light, stress, and aging also cause the potato to produce chaconine and solanine. The appearance of chlorophyll is thus a warning that something is wrong with the potato. Secondly, avoid eating potato peels. About 30% to 80% of the glycoalkaloid content of a potato is in its peel with the remainder in the flesh of the tuber. Fortunately, these compounds are not well absorbed by the gastrointestinal system and are soon eliminated in the feces.
Does Cooking Inactivate These Compounds?
It depends. Boiling, microwaving, and freeze-drying are relatively ineffective. Deep-frying at 170oC (340oF) does reduce the levels of chaconine and solanine.
How Do Chaconine and Solanine Benefit the Plant?
They are believed to provide resistance to insects and fungi.
What the Web Has to Say about:
Chaconine and Solanine
Chaconine
and Solanine
Review of the toxicology literature related to these compounds. Prepared for
the US National Institute of Environmental Health Sciences.
Nature's
Chemicals and Synthetic Chemicals: Comparative Toxicology
The bevy of naturally occurring toxic compounds in foods. Proceedings of the
National Academy of Sciences paper by Bruce N. Ames, University of
California at Berkeley.
New
Safeguards Against Glycoalkaloids
Using a monoclonal antibody to detect these poisons. From the Agriculture Research
Service, US Department of Agriculture.
Nightshade
(Solanum spp.) Biology
Outline of the weeds in this genus. From Rebecca Goodhue, Iowa State University.
Potato
Glycoalkaloid Toxicity
Reviews occurrence, structure, and toxicity of these compounds. From Andrew
Montario, Cornell University.
Solanine
and Chaconine
Structure and enzymology of these compounds as presented in the ESTER database.
From Agro de Montpellier.
Solanum's
Home Page
Investigations into glycoalkaloid accumulation in potatoes. Dissertation work of
Everard J. Edwards, Nottingham Trent University.
Steroid
Alkaloids
Physiologically active toxins found in potatoes, tomatoes, and some other
plants. From Cornell University.
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