Alkaloids are organic compounds, mainly derived from amino acids and
containing nitrogen, found in plants. Alkaloids are water-soluble, bitter in
taste and have powerful physiological properties. They protect plants against
plant-eating animals and attack by insects, parasites, and competitors.
Major alkaloid groups of concern from the standpoint of human consumption
include pyrrolizidines, xanthines and solanines. Others are mainly consumed by
grazing animals and can be potentially transferred to humans through milk.
Hepatotoxic effects have been reported for some Chinese herbal medicines
(such as Jin Bu Huan, Ma-Huang and Sho-saiko-to), pyrrolizidine
alkaloid-containing plants, germander (Teucrium chamaedrys), chaparral (Larrea
tridentata), Atractylis gummifera, Callilepsis laureola, and others. Severe
liver injury, including acute and chronic abnormalities and even cirrhotic
transformation and liver failure, has been described after the ingestion of a
wide range of herbal products and other botanical ingredients, such as
mushrooms. It is concluded that in certain situations herbal products may be
just as harmful as conventional drugs.
Potatoes contain α-solanine and α-chaconine, two well-known toxic steroidal glycoalkaloids (SGAs). Sprouts and green tubers accumulate especially high levels. The amount of glycoalkaloids increases upon wounding and light exposure. Mild clinical symptoms of glycoalkaloid poisoning include abdominal pain, vomiting, and diarrhea. More serious cases have experienced neurological problems, including hallucinations and paralysis, and fatalities have also been recorded. To avoid postharvest increases in SGAs, harvested potatoes must be stored in the dark at low temperature. In potato breeding, introducing wild potato species as a genetic resource could increase the SGA level.
Other pyrrolizidine alkaloids, such as monocrotaline may cause pulmonary
hypertension and right heart congestive failure.
At least six species of plants including threadleaf groundsel (Senecio
longilobus), Japanese butterbur (Petasites japonicus), coltsfoot
(Tussilago farfara), comfrey ( blackwort) (Symphytum officinale),
giant leopard plant, giant ligularia (Farfugium japonicum), and Aleutian
ragwort (Senecio cannabifolis), have been shown to induce the following
types of cancer: liver cancer, skin cancer, cancer of intestinal tract and
lungs. Solanum alkaloids, including solanine, chaconine, and tomatine, are found in potato, eggplant, and tomato, among others.