Hypoglycin B

Hypoglycin B

Hypoglycin B is a naturally occurring amino acid found in certain plants, most notably in the species belonging to the Sapindaceae family, such as the Ackee tree (Blighia sapida). It is closely related to hypoglycin A, another toxic amino acid found in the same plants. Hypoglycin B, like hypoglycin A, is associated with causing a severe and sometimes fatal illness known as Jamaican vomiting sickness, which results from the ingestion of unripe or inadequately prepared ackee fruit. The toxicity of these compounds is due to their ability to inhibit various enzymes involved in fatty acid oxidation and amino acid metabolism, leading to the accumulation of harmful metabolites and severe metabolic disturbances.

Chemical Structure and Mechanism of Action

Hypoglycin B is characterized by its unique chemical structure that allows it to interfere with the normal metabolic processes within the cell. It acts primarily by inhibiting the enzyme medium-chain acyl-CoA dehydrogenase (MCAD), which plays a crucial role in the beta-oxidation of fatty acids. This inhibition leads to a decrease in the production of adenosine triphosphate (ATP) and an accumulation of fatty acids and their derivatives, causing hypoglycemia and metabolic acidosis.

Clinical Manifestations

The ingestion of hypoglycin B-containing plants, particularly unripe ackee fruit, can lead to a range of clinical symptoms associated with Jamaican vomiting sickness. These symptoms include vomiting, abdominal pain, dizziness, and in severe cases, seizures, coma, and death. The onset of symptoms typically occurs a few hours after ingestion of the toxic substance.

Diagnosis and Treatment

Diagnosis of hypoglycin B poisoning is primarily based on the clinical presentation and a history of exposure to the toxin. Laboratory tests may reveal hypoglycemia, metabolic acidosis, and elevated levels of certain fatty acids and their metabolites. Treatment is supportive and focuses on correcting hypoglycemia and acidosis, as well as preventing further intake of the toxin.

Prevention

Prevention of hypoglycin B poisoning is largely dependent on public education regarding the proper identification and preparation of ackee fruit. Only fully ripe ackee fruits, which have naturally opened on the tree, should be consumed, and all parts of the fruit except the arils (edible portions) must be discarded.

See Also

• Amino acid metabolism
• Fatty acid oxidation
• Metabolic acidosis
• Hypoglycemia