Appearance Brownish needles | ||
Divicine (2,6-diamino-4,5-dihydroxypyrimidine) is an oxidant and a base with alkaloidal properties found in fava beans and Lathyrus sativus. It is an aglycone of vicine. A common derivative is the diacetate form (2,6-diamino-1,6-dihydro-4,5-pyrimidinedione).
Contents
Occurrence
Divicine is found in fava beans and in the legume Lathyrus sativus, also known as khesari, which is a cheap and robust food source commonly grown in Asia and East Africa.
Synthesis
In plants, reduced divicine is formed from the hydrolysis of the inactive β–glucoside, vicine.
A simplified three-step process for artificial divicine synthesis: (1) The benzyl group of 2-amino-5-benzyloxy-4-hydroxypyrimidine is removed by acid hydrolysis, yielding 2-amino-4,5-dihydroxypyrimidine. (2) This intermediate is then treated with nitrous acid to yield the slightly soluble orange product, 2-amino-6-nitrosopyrimidine-4,5-diol (3) which is then reduced with sodium dithionite to yield divicine.
Toxicity
Divicine has been deemed a hemotoxic component of fava beans and plays a role in the development of favism, a disorder that involves a hemolytic response to the consumption of broad beans due to glucose-6-phosphate dehydrogenase (G6PD or G6PDH) deficiency. This deficiency, an X-linked recessive hereditary disease, is the most common enzyme deficiency worldwide. It is particularly common in those of African, Asian, Mediterranean, and Middle-Eastern descent. Symptoms of favism include hemolysis, prolonged jaundice, kernicterus, and even acute renal failure in extreme cases.
The specific mechanism of divicine’s toxicity is still unknown. It had been established that the β–glucosides vicine and convicine were linked to the precipitation of hemolytic crises in G6PDH-deficient individuals, but in a more recent study of rat erythrocyte toxicity, exposure to 1.5 mM of divicine dramatically reduced survival rates while exposure to 5 mM of vicine did not. These results suggest that divicine is a direct-acting hemolytic agent and likely the direct cause of favism.
Divicine is also present in and at least partially responsible for the poisonous action of Lathyrus sativus - a legume commonly grown in drought- and famine-prone regions of Asia and East Africa as an ‘insurance crop’ for human consumption and livestock feed when other crops fail to grow, despite their known health hazards.