Metabolism of intraruminally administered [4-¹⁴C]formononetic and [4-¹⁴C]biochanin a in sheep

Abstract

Two ovariectomized ewes were given a single intraruminal dose of [4-14C]- labelled isoflavone and slaughtered 6 hr later. In the ewe given [4-14C]biochanin A, labelled genistein was detected in addition to labelled biochanin A in the blood plasma, urine, kidney, liver, bile, contents of the rumen, and those of the small intestine. p-Ethylphenol, which is almost certainly a metabolite of biochanin A, was present in the urine but not labelled, which indicates that it originates from ring B of the isoflavone molecule. In the ewe given [4-14C]formononetin, a similar distribution of the isoflavone and its demethylation product, daidzein, was found. In addition, labelled equol was found in the blood plasma and urine. Another labelled metabolite, identified as O-desmethyl angolensin (2,4-dihydroxyphenyl p-hydroxy-ß-methylbenzyl ketone), was also found in the urine. In the urine from both ewes, there were also labelled light petroleuminsoluble acidic compounds but they were not identified.