Ackee Toxin : a Riboflavin Antimetabolite?

Acute encephalopathy in children in Muzaffarpur, India: a review of aetiopathogenesis

The acute encephalopathy occurring in children in Muzaffarpur, India, also recognised in other litchi-cultivating areas of India, Bangladesh, Vietnam and China, had previously been linked to litchi consumption. Recently, it has been identified as hypoglycaemic encephalopathy of an unusual aetiology with three key factors: undernutrition, prolonged fasting and litchi consumption. A second set of investigators has independently reconfirmed the diagnosis and the three-factor aetiology. Skipping the evening meal with an intake of large amounts of litchi in undernourished children is causative. Early-morning hypoglycaemia with an inadequate glycogen store leads to initiation of gluconeogenesis and fatty acid β-oxidation, but methylene cyclopropyl alanine and glycine present in the litchi aril block the fatty acid β-oxidation cycle. The outcomes are uncorrected hypoglycaemia and encephalopathy due to the entry of metabolic intermediates that cross the blood-brain barrier and affect neuronal function. Suggested measures include early 10% dextrose infusion. Awareness about the disease is of prime importance. The diagnosis and aetiopathogenesis are still under question from a part of the scientific community. This review was undertaken to present a comprehensive view of hypoglycaemic encephalopathy and to remove some of the lingering doubts.

Toxicants in plants and plant products

Toxicants are widely distributed in plants and plant products, including intentionally added, incidentally added, and naturally occurring food toxicants. This review covers the toxicity of some food additives: the distribution, residues, toxicity, and methods of removal of some pesticides and toxic metals; and the presence of naturally occurring toxicants in plants and plant products. Extensive review has been done, particularly on natural toxicants. However, there are still extensive gaps in our knowledge pertaining to effect upon the health of many of the substances known to be present in natural plant food products, as well as even the identity of many natural chemical components of plant foods and their potential toxicological significance. An understanding of their presence, formation, and toxicity is important as far as public health is concerned.

Metabolites of riboflavine in milk, urine and tissues of animals in relation to alimentary symbiotic bacteria

1. Riboflavine given orally to sheep, calves, goats and ruminating kids gave rise, in milk and urine, to extra riboflavine accompanied by hydroxyethylflavine, by formylmethylflavine and by other as yet unidentified metabolites, but subcutaneous injection of riboflavine caused prolonged excretion of riboflavine in urine and milk unaccompanied by metabolites.

2. Placement of riboflavine by means of fistulas into the rumen, the abomasum or the caecum and abstraction of samples from the rumen or caecum showed that the rumen was the site of origin of the metabolites, thus accounting for the lapse of time of several hours between the ingestion of riboflavine and the appearance of hydroxyethylflavine in the urine and the absence of metabolites after subcutaneous injection of riboflavine.

3. Kids in which rumination had not yet become established could not produce metabolites from ingested riboflavine although, when fed milk containing the metabolites, they readily excreted them in their urine.

5. Incubation in vitro of kidney or liver tissue from cattle or goats with riboflavine did not give rise to metabolites, but these tissues could both reduce formylmethylflavine to hydroxyethylflavine in vitro.

6. Post-mortem examination of animals to which riboflavine had been fed showed the presence of metabolites only in gut contents, in the urinary bladder and in the bile. When injected, riboflavine reached the bile but no metabolites were produced.

7. Metabolites were found to occur naturally in the urine of ruminants in small amounts. Hydroxyethylflavine was readily demonstrable in the urine of the rabbit, but in the urine of the dog metabolites could not be found.

8. From these and earlier and later experiments the conclusion is drawn that riboflavine metabolites arise in the ruminant from the degradation of riboflavine by rumen bacteria.