The phyto-estrogens formononet in (7-hydroxy-4 methoxylsoflavone) and biochanin A (5-7-dlhydroxy-4-methoxylsof lavone) were independently incubated in vitro at 39~ in bovine rumen fluid from a fistulated steer receiving an alfalfa hay

I The phyto-estrogens formononet in (7-hydroxy-4 methoxylsoflavone) and biochanin A (5-7-dlhydroxy-4-methoxylsof lavone) were independently incubated in vitro at 39~ in bovine rumen fluid from a fistulated steer receiving an alfalfa hay diet. Formononet in was incubated in studies 1 and 2, whereas biochanin A was incubated in s tudy 3. The isoflavones were separated and quantified by high performance liquid chromatography. In study 1, formononet in concentration, 14.80 /~ /ml at t ime 0, declined to 1.16/~g/ml by 12 h and to .76 /ag/ml by 24 h. Daidzein (7,4"-dihydroxyisoflavone), .18 #g/ml at t ime 0, peaked at 12 .92/ lg /ml at 6 h and decreased to 1.30 #g/ml by 24 h. Equol (7,4'-dihydroxyisoflavan), detected at 6 h, peaked at 16.94 gtg/ml at 18 h and dropped to 12.64 #g/ml at 24 h. In incubation study 2, formononetin declined from 17.57 gtg/ml at t ime 0 to 7.08/ag/ml by 6 h. Daidzein concentration was 1.75 #g/ml at t ime 0 and increased to 12.03 /ag/ml by 6 h. Equol was detected at 3 h and increased to 2.32 gtg/ml at 6 h. The half-lives were 4.3 for formononet in and 9.8 h for daidzein in this in vitro system. In study 3, biochanin A, 8.54 /.tg/ml at t ime 0, decreased to 0 gtg/ml by 12 h in incubation 3, whereas genistein (5,7,4'-trihydroxyisoflavone), 3.17 gtg/ml at 1 h, peaked at 7.35/ag/ml at 4 h and decreased to .32 gtg/ml at 24 h. Equol was not detected in incubation study 3. The half-lives of biochanin A and genistein were 3.9 and 5,5 h, respectively. Bovine tureen fluid metabolism of formononetin yielded daidzein and equol, but the only identified product of biochanin A was genistein. (