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Methylene cyclopropyl acetic acid (MCPA) is found in lychee seeds and also a toxic metabolite in mammalian digestion after ingestion of hypoglycin.
Contents
Overview
Methylene cyclopropyl acetic acid (MCPA) is a compound found in lychee seeds. It is also a metabolite in mammalian digestion after ingestion of hypoglycin, a rare and potentially toxic amino acid, chemically related to the common amino acid lysine. (Hypoglycin is found in the unripe ackee fruit in Africa.)
Dihydrosterculic acid is the major carbocyclic fatty acid in the seed oils of Litchi chinensis. It is a cyclopropene fatty acid; these have been found in many plants of the order Malvales (Sterculiaceae, Malvaceae, Bombaceae and Tiliaceae), in up to 60% of seed oil content, depending on the species but also in leaves, roots and shoots. They are accompanied by small amounts of their cyclopropanoid analogues, i.e. cyclopropyl acetic acid.
Symptoms and signs of poisoning
The symptoms of poisoning are intolerance to prolonged fasting, vomiting, altered mental status with lethargy, progressing to unconsciousness, coma and death.
Mechanism of toxicity per animal studies
MCPA is a potent inhibitor of acyl CoA dehydrogenase, thus preventing the metabolism of fatty acids. The intolerance to prolonged fasting is due to inability to switch from glucose to fatty acid oxidation, impaired ketogenesis. There is increased urinary excretion of dicarboxylic acids, due to omega oxidation that occurs in the endoplasmic reticulum.