Jd. Cremin et al., EFFECTS OF REDUCED PHENOLIC-ACIDS ON METABOLISM OF PROPIONATE AND PALMITATE IN BOVINE LIVER-TISSUE IN-VITRO, Journal of dairy science, 77(12), 1994, pp. 3608-3617
Benzoic acid, 3-phenylpropionic acid, trans-cinnamic acid, and 3-(4-hy
droxyphenyl)propionic acid in ruminal fluid are presumed to be the pro
ducts of chemical reduction of dietary phenolic monomers by ruminal mi
croorganisms. Effects of reduced phenolics on metabolism in bovine liv
er tissue were evaluated by measurement of 1) conversion of propionate
to glucose and CO2, 2) conversion of palmitate to oxidized products,
and 3) leakage of lactate dehydrogenase from liver slices in vitro. In
Experiment 1, .4 mM benzoic, 3-phenylpropionic, trans-cinnamic, or 3-
(4-hydroxyphenyl)propionic acids decreased conversion of propionate to
glucose and decreased conversion of palmitate to total oxidation prod
ucts. At .2 mM, 3-(4-hydroxyphenyl)propionic acid did not inhibit conv
ersion of propionate to glucose compared with that of controls, but th
e other reduced phenolics did. In Experiment 2, the same reduced pheno
lics inhibited conversion of propionate to glucose. Of the reduced phe
nolics tested, cinnamic acid inhibited conversion of propionate to glu
cose at the lowest concentration, .1 nM. Additionally, when present at
greater than or equal to 1.4,.1, or .005 mM, benzoic, 3-phenylpropion
ic, or trans-cinnamic acids, respectively, increased leakage of lactat
e dehydrogenase from liver tissue. The reduced phenolics tested, which
are representative of those in ruminal fluid, inhibited metabolism of
bovine liver tissue in vitro at supraphysiological concentrations. Da
ta at physiological concentrations were inconclusive.