Turnover and hydrolysis of vicine and convicine in avian tissues and digesta

The objectives of this study were to establish factors influencing the absorption, excretion and hydrolysis of vicine and convicine in chicks. Blood vicine, following the oral administration of a single dosage of vicine into the crop of young chicks, reached maximum concentrations within 3 h. It was nearly completely removed from the blood within 12 h and had a half‐life of approximately 4.5 h. The accumulation and excretion patterns of vicine in the liver and kidney were similar to those of the blood except that the concentrations were much higher in these tissues, particularly the kidney. Bile also contained a very high concentration of vicine which tended to accumulate following the decline in other tissues. These results together with the appearance of vicine in the urine of colostomised birds suggest that vicine is excreted in the urine and bile. Convicine in contrast to vicine was not absorbed by the chick. In‐vitro studies were carried out with tissue and digesta homogenates from the chick in order to establish the site(s) at which vicine and convicine were hydrolysed to their aglycone forms. The results demonstrated that neither vicine nor convicine were hydrolysed in the presence of liver, kidney, intestinal wall or caecal wall homogenates, digesta from the large intestine or by enzymes present in whole or ground fababeans. They were, however, slowly hydrolysed in the presence of 0.1N HCl at 37°C and very rapidly hydrolysed by digesta from the caeca. Antibiotic additions to the diets markedly reduced the in‐vitro rate of hydrolysis of these compounds. The latter results suggest that vicine and convicine are hydrolysed by microorganisms in the caeca of the chick but are not hydrolysed by the micro‐organisms in the gastrointestinal tract, by endogenous tissue enzymes or by enzymes present in fababeans and only minimally hydrolysed by the low pH of the stomach.