EFFECTS OF REDUCED PHENOLIC-ACIDS ON METABOLISM OF PROPIONATE AND PALMITATE IN BOVINE LIVER-TISSUE IN-VITRO

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.